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415 Cards in this Set
- Front
- Back
Two systems of internal communication and regulation in multicellular organisms |
Nervous system Endocrine system |
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Nervous system vs endocrine system |
Nervous = -rapid, short-acting responses -message sent to a specific cell Endocrine= -slower, longer lasting response -message sent to cells throughout body but only received by specific cells |
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Berthold's Experiment |
Observed male roosters were aggressive and had large waddles and cones and large testes -removed tests: males lost secondary sex characteristics ---> testes necessary -removed one teste and put in abdominal cavity: male still had secondary sex characteristics ---> testes sufficient -Concluded that testes secretes a substance which conditioned blood and blood acted on chicken to produce secondary sex characteristics (substance later found to be testosterone |
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Classify signaling molecules based on distance of target |
hormones = affect distant target cells; transported via bloodstream paracrines = affect neighboring cells; through ECF but probably not blood autocrines = affect same cell that secretes them (some paracrines and hormones can have autocrine functions) |
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examples of paracrines |
neurotransmitters; cytokines |
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Endocrine cells
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Cells that secrete hormones |
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Sources of hormones |
1) Isolated endocrine cells in a tissue 2) Endocrine Glands = aggregation of endocrine cells that secrete hormones into ECF; ductless glands (as opposed to exocrine grands) 3) Neurosecretory Cells = specialized nerve cells; secret neurotransmitters that diffuse into blood and act on distant targets -- called neurohormones |
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Chemical Classes of Hormones & whether lipid or water soluble |
1) Peptides or Proteins -Water Soluble *ex: Insulin and growth hormone 2) Steroid Hormones -synthesized from steroid cholesterol -Lipid Soluble *ex: Estrogen and Progesterone 3) Amine Hormones -Synthesized from amino acid, typically tyrosine -Some are lipid soluble, some are water soluble *ex: epinephrine + TH |
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How water soluble hormones signal |
--Can't freely cross plasma membrane, but can travel freely in blood: -Packaged in vesicles and secreted by exocytosis -travels freely in blood -binds to receptor on cell surface of target cell, triggering a signal transduction pathway: ---leads to responses in cytoplasm, activating or inactivating an enzyme or altering gene expression |
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How lipid soluble hormones signal |
--Can diffuse through plasma membrane but can't travel freely in blood -diffuses through plasma membrane -binds to transport proteins in blood - keeping it soluble in blood -diffuses into target cell -binds to receptor either in nucleus or cytoplasm ---bound hormone receptor alters gene expression |
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first hormone identified |
secretin |
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Hormone action depends on: |
Cell type & Receptor Type -different cells have different signaling cascades, leading to different responses (as do different receptors) |
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Epinephrine secretion and effects
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-Sympathetic Division of Nervous System stimulates endocrine glands to secrete epinephrine
-different effects on different cells: --Liver - breaks down glucose (binds to beta receptor) --Blood vessels in skeletal muscles dilate (binds to beta receptor) --Blood vessels in intestines constrict (binds to alpha receptor) |
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Evolution of hormone signaling molecules |
Hormone signaling molecules are highly conserved --find same compounds and same receptor in many organisms, although the systems have diversified to serve different functions |
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Simple Endocrine Pathway: |
Stimulus causes Endocrine Cell to Release Hormone which travels in blood to Target Cell triggering a response of target cell -- can act as negative or positive feedback |
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Simple Neuroendocrine Pathway: |
Stimulus causes Sensory Neuron to Respond stimulating Neurosecretory Cell to release a Neurohormone which travels in blood to Target Cell triggering a response -- can act as negative or positive feedback |
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Oxytocin - example of neuroendocrine pathway: |
1) Stimulus = baby suckling on breast 2) Sensory neuron stimulates neurosecretory cells to release oxytocin 3) Oxytocin travels through body and binds to receptors on smooth muscle of mammalary glands 4) Causing release of milk 5) Acts as + feedback, causing baby to suckle more |
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What part of the body regulates hormone secretion
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hypothalamus and pituitary gland |
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Hypothalamus's role in hormone secretion |
Control Center - integrates nervous and endocrine systems to maintain homeostasis |
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Pituitary Gland - role in hormone secretion |
Master Gland for hormone secretion and control: -interface between nervous and endocrine systems -still gets its control from hypothalamus |
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2 Glands of Anterior Pituitary- Origins + What type of cells it includes |
1) Anterior Pituitary -Originates from gut epithelial tissue -Contains glandular (endocrine) tissue cells 2) Posterior Pituitary -Originates from neural tissue -Contains axons from hypothalamic nerve, which go directly into the posterior pituitary |
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Anterior pituitary - overview |
-Originates from gut epithelial tissue -Contains glandular (endocrine) tissue cells ---the cells produce & secrete specific hormones -----some of which are tropic hormones ("in turn" cause release of hormones from other glands) -Have actual release AND synthesis of hormone here |
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Control of hormone secretion in anterior pituitary |
Controlled by Hypothalamus: -hypothalamic neurons lead to release of hypothalamic releasing hormones or release-inhibiting hormones --these hypothalamic neurhormones reach anterior pituitary traveling through the hypothalamic pituitary portal system (which only goes from nerve terminals of hypothalamic nerves to AP glandular tissue) |
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Anterior Pitutitary Hormones to Remember; -which are tropic |
FLAT PEG: TROPIC: FSH and LSH = follicle stimulating hormone and luteinizing hormone -Stimulates testes and ovaries to produce testosterone and pregestins, estrogen ACTH = Adrenocorticotropic Hormone -Stimulates adrenal cortex to produce corticosteroids TSH = Throtropin (thyroid stimulating hormone) -Stimulates thyroid to produce Thyroid Hormone Not-Tropic: Prolactin = Stimulates mammalary glands (to produce milk) Endorphins and Enkephalins = analgesic effects GH = growth hormone; stimulates bones (leads to bone growth) |
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Anterior Pituitary Hormone Secretion pathway |
Stimulus --> Stimulates/inhibit Hypothalamus ---> releases hormones which travel to Anterior Pituitary ----> Releases Tropic Hormones ---> which travels to Endocrine Gland ---> Releases Hormone Hormone can act as negative feedback on stimulus; Tropic hormone can ALSO act as negative feedback on stimulus |
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Posterior Pituitary |
-Originates from neural tissue -contains axons from hypothalamic neurons -hormone synthesis occurs in hypothalamus and hormone is transported down axons to posterior pituitary where hormones are stored and released -Secretes 2 hormones: --Antidiuretic Hormone (ADH) - targets kidney tubule to increase water retained by kidneys --Oxytocin - Targets mammalary glands and uterine muscles to stimulate milk flow, uterine contractions, also "cuddle hormone" |
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thyroid gland |
consists of many follicles (composed of follicle epithelial cells and colloid) and parafollicular cells (C-Cells) in between |
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Two types of hormones secreted by Thyroid Gland |
1) Calcitonin 2) Thyroxin |
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Calcitonin |
Produced by Parafollicular Cells (C-Cells) of thyroid
-Helps regulate calcium homeostasis |
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Thyroid Hormone - overview |
Produced by follicle epithelial cells of thyroid -increases metabolism; essential fro growth and neural development -Contains both T3 (triiodothyronine) and T4 (thyroxine) |
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T3 and T4 names |
T3 = triiodothyronine T4 = thyroxine |
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How are T3 and T4 produced (and list steps) |
Via iodination of tyrosine in the follicular cells of throid: 1) Thyrglobulin, which contains ~100 tyrosines, is produced by follicle epithelial cells and secreted into follicle lumen 2) Iodide is actively transported (via iodide pumps) from capillary -> epithelial cell -> Follicle lumen 3) Iodination of Tyrosine Units of Thyroglobulin in follicle lumen 4) Endocytosis of thyroglobulin into epithelial cells 5) Hydrolysis of Thryroglobulin epithelial cells by lysosomal proteases 6) Release of T3 and T4 into circulatory system |
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T4 vs T3 |
T4 = prohormone b/c has little metabolic activity T3 = active form - capable of binding nuclear thyroid hormone receptors Thyroid releases 10x more T4 than T3 T4 can be converted to T3 - thus additional layer of control of TH signaling |
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Deiodinases |
Deiodinases = enzymes that can remove iodine moieties from TH: thus controlling activation and inactivation ot TH within a cell Type 2 Deiodinase = Activating Deiodinase -Convertes T4 -> T3 by removing outer ring of iodine Type 3 Deiodinase = Inactivating Deiodinase -Converts T4 -> rT3 (reverse T3), which is inactive -Also converts T3 -> T2 (inactive also) -does this by removing inner ring of iodine --Deiodinase activity is controlled in time and tissue specific manners |
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2 ways to get T3 |
1) Secreted by thyroid 2) Type 2 deiodinase converting T4 -> T3 |
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How does T3 lead to response in target cell |
1) Lipid-Soluble T3 readily enters the cell 2) T3 binds to receptor - on cell nucleus (called thyroid hormone receptor) 3) Receptor sits on promoters of genes sensitive to thyroid hormone, called thyroid hormone responsive elements (TRE) thus causing gene transcription upon binding 4) Gene Products are responsible for multiple actions of thyroid hormone |
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Functions of Thyroid Hormon |
Increases: Metabolic activity of whole body Heat Production Heart Rate & strength of heart rate Growth Rate & Bone maturation Mental Processes |
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Insufficient TH in perinatal period causes: |
Cretinism Impaired development of skeletal system, CNS, severe mental retardation, short statured, potbellied, coarse facial features, protruding tongue |
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Regulation Pathway of Thyroid Hormone |
1) Hypothalamic Neurons secrete Thyrotropin Releasing Hormone (TRH) into Portal Vessels 2) TRH travels to AP and stimulates thyrotroph cells to secrete Thyroid Stimulating Hormone (TSH) into circulatory system 3) TSH binds to receptor in thyroid and stimulates thyroid to synthesize and secrete Thyroid Hormone - T3 & T4 4) Negative Feedback: TH decreases sensitivity of thyrotrophs to TRH and also decreases release/production of TRH by hypothalamus |
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Hypothyroidism |
Main cause: Grave's Disease - autoimmune disorder involving antibodies to TSH receptor, mimicking TSH - increased TH production b/c Thyroid max stimulated (by antibodies binding to TSH receptor)---> causing hyperplasia/hypertrophy of thyroid follicular cells (causing goiter) -TSH levels low (due to negative feedback from high TH) -symptoms: high metabolic rate, heat intolerant, etc. |
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hyperthyroidism |
Main cause = iodide deficiency -decreased TH (b/c don't have iodination of thyroglobulin) -TSH levels high (b/c don't have negative feedback from TH) --> Max stimulation of thyroid (leads to goiter) Symptoms = low metabolic rate, cold intolerant, etc. |
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TSH and TH levels in hypothyroidism and hyperthyroidism & how both lead to goiter |
Hypothyroidism: high TH (b/c antibody binding) low TSH (b/c negative feedback from TH) --> goiter results from antibody stimulating thyroid Hyperthyroidism low TH (b/c not getting iodination of thyroglobulin) high TSH (b/c no negative feedback from TH) ---> goiter results from high TSH stimulating thyroid |
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3 organ systems involved in calcium homeostasis (and what they each do) |
bone = deposition and absorption of bone kidney = excretion of calcium intestine = absorption of calcium |
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3 hormones involved in calcium homeostasis |
Calcitonin = inhibits osteoclasts ---> blood calcium levels fall Parathyroid Hormone = stimulates bone turnover and decreases Ca2+ exretion by kidne ---> blood calcium levels rise Calcitriol = promotes absorption of Ca2+ from GI --> blood calcium levels rise |
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Calcitonin |
plays role in ca2+ homeostasis Calcitonin = inhibits osteoclasts ---> shifts balance to osteoblasts (which use Ca2+ from blood to make new bone); thus blood calcium levels fall *Not a major player in adult human Ca2+ homeostasis -secreted by thyroid |
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Parathyroid Hormone |
plays role in ca2+ homeostasis Secreted from Parathyroid Glands (4 small structures on posterior surface of thyroid) -Ca2+ activates receptors on parathyroid cells which inhibit PTH ---low levels of Ca2+ trigger release of PTH PTH increases blood calcium levels by: -Stimulating bone turnover -decreasing calcium excreted by kidneys -activating Calcitriol in kindey |
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Calcitriol |
plays role in Ca2+ homeostasis synthesized from Vitamin D (which has 2 sources - diet & synthesis in skin from cholesterol in presence of UV light) in liver and kidney Final step of conversion to Calcitriol occurs in kidney and is activated by PTH --> promotes absorption of Ca2+ from GI to raise blood calcium levels |
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Glucose |
key fuel for body; when we eat our body breaks food down to form glucose |
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Insulin |
hormone that allows glucose to get into cells and provide the energy they need |
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how is insulin released & how does it lead to uptake of glucose |
-secreted by beta cells of pancreas & travels through body (as does glucose) -when insulin binds to a cell - activates glucose transporters in cell membranes to pull glucose in --when glucose is absent, transporters are returned to cytoplasm and glucose uptake is inhibited |
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Diabetes Mellitus |
Group of diseases marked by hyperglycemia (high glucose levels in blood b/c not entering cells) due to defective insulin production, action, or both |
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Type 1 Diabetes vs Type 2 |
Type 1 = lack of insulin Type 2 = lack of insulin responsiveness in target cell |
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Diabetes results in... |
Lack of metabolic fuel: -can lead to blindness, kidney failure, heart disease, and stroke |
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Treatment of diabetes |
Type 1 = insulin injections Type 2 = also insulin injections, b/c body needs a lot since cells less responsive |
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Hormones involved in Glucose Homeostasis |
Insulin & Glucagon |
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How does insulin regulate glucose homeostasis |
decreases blood glucose levels: -after eating, glucose levels rise --> insulin is secreted (by beta cells in pancreas) --> stimulates muscle, adipose, liver to take up glucose --> blood glucose levels fall |
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How does glucagon regulate glucose homeostasis |
increases blood glucose levels: -when fasting, blood glucose levels fall --> glucagon is secreted (by alpha cells in pancreas) --> stimulates liver to convert glycogen to glucose --> blood glucose levels rise |
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Adrenal Gland |
Endocrine gland within a gland - composed of adrenal medulla and adrenal cortex
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Adrenal Medulla |
Inside portion of adrenal gland: -under nervous system control (develops from nervous tissue) -Produces sympathetic hormones: epinephrine and norepinephrine ---> fight or flight hormones |
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Adrenal Cortex |
Outer portion of adrenal gland: -Under hormonal control -Produces steroid hormones --> which can be divided into 3 functional groups: the three S's "Salt, Sex, and Sugar" |
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Hormone Groupings Secreted by Adrenal Cortex |
Sal/Sex/Sugar: (1) Mineralcorticoids = for salt and water homeostasis; effects on kidneys --ex: aldosterone: stimulates kidneys to conserve Na+ and excrete K+ (2) Sex Steroids = for sexual behavior and development --amounts negligible compared to gonads (although testosterone secretion by females here could become critical if something wrong) (3) Glucocorticoids = regulate glucose levels and also protein and fat metabolism *main glucocorticoid in human = cortisol = stress hormone |
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Main glucocorticoid |
cortisol = stress hormone released in times of physical or emotional stress; -triggers non-critical cells to decrease glucose uptake -immune system reactions are blocked |
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Production pathway for cortisol |
Stressor ---> Hypothalamus secretes Corticotropin-Releasing Hormone (CRH) which travels to AP via portal system --> AP secreates Adrenocorticotropic Hormone which travels in blood to adrenal cortex --> Adrenal Cortex secretes Cortisol -Cortisol acts as negative feedback on AP and hypothalamus |
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Different pathways in Adrenal Gland |
-Corticosteroids from adrenal cortex = respond to long-term stress: ---Hypothalamus (hormone signal) -> AP (hormone signal) -> Adrenal Cortex (corticosteroid) -Catecholamines from adrenal medulla = short term stress: ---Hypothalamus (nerve impulse) -> Adrenal Medulla (catecholamines) |
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Production of Sex Steroids occurs in _____ in response to _______ from ______ |
Occurs in gonads in response to Gonadotropins (LH and FSH) from Anterior Pituitary |
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How is LH and FSH release controlled |
By hypothalamic Gonadotropin Releasing Hrmone (GnRH) - which increases release during puberty |
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Male Gonads - what they are, and what they secrete |
Testes -secrete androgens; with primary androgen geing testosterone |
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Male Secondary Sex characteristics |
Axillary and Public Hair Deepening of voice Muscle Growth |
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Femal Gonads - what they are and what they synthesize |
Ovaries -Synthesize Estrogens and Progesterone ---main estogen = estradiol |
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Female secondary sex characteristics |
Axillary and pubic hair breat growth body fat redistribution inditation of menstrual and ovarian cycles |
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What determines whether fetus becomes phenotypically male or female?
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Sex Hormones: -Early embryo, gonads undifferentiated -around 7th week - ---androgens are produced in presence of Y-chromosome -- male reproductive structures form ---if lack androgens --- female reproductive structures form |
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Goals for studying hormone action |
1) Detect, identify, and measure hormone 2) Identify and characterize receptors 3) determine signal transduction pathways in different tissues |
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Immunoassay |
Can be used to detect and measure hormones =techniques that use interactions between antigen (hormone) and an antibody to that antigen; can measure half life of hormone -create a standard curve: measure radioactivity of different known concentrations (when have known concentration of known labeled, here radioactive hormone). -Then measure the radioactivity of unknown concentration (again with same amount of known labeled concentration). -find where on the standard curve unknown concentration falls (in terms of radioactivity) to determine concentration amount |
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Affinity Chromotography |
Allows you to identify receptors and quantify them -wash a column containing beads with hormone of interest -hormone binds to bead -run proteins through column -proteins with stick to hormone bound to the bead - these are the receptors for that hormone -one hormone can bind to multiple receptors -can create drugs to block specific receptors and thus specific responses |
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What type of Receptors to Epinephrine and Norepinephrine bind to in cells of the body |
Adrenergic Receptors |
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Sexual reproduction |
Creation of offspring by fusion of 2 haploid cells (gametes) to form a diploid zygote |
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gametes that fuse to form zygote |
Sperm and egg |
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Asexual reproduction; description and types |
Creation of new individuals without fusion of gametes 3 types: 1) Budding: New individuals form from bodies of older animals (by mitosis) -genetically identical to parent 2) Regeneration: Fragment of organism forms complete organism (by mitosis) -genetically identical to parent 3) Parthenogenesis: Development of offspring from unfertilized egg -progeny is haploid OR diploid -most of these species also engage in sexual reproduction -may be identical to parent or not |
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Pros and cons of sexual and asexual reproduction |
Sexual: pros= -Genetic diversity is created; through which evolution acts cons = -less efficient (only 50% of pop produces offspring) -mating behavior has costs and risks Asexual pros = -no energy for mating -don't have to find mate -preservation of successful phenotype = good in constant environments cons = -doesn't result in genetic changes = bad in non-constant environments |
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How to get genetic diversity |
3 Ways: Gametes produced during meiosis produces genetic diversity 2 ways: 1) Crossing over between homologous chromosomes 2) independent assortment of chromosomes (which homologue goes to which daughter cell is random) Third way: have different individuals 3) Variation of genetics between any two parents |
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Steps of Sexual Reproduction |
1) Gametogenesis = making gametes *spermatogenesis and oogenesis 2) Mating = getting gametes together 3) Fertilization = fusing gametes * sperm (n) + Egg (n) = Zygote (2n) |
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Which step(s) of sexual reproduction are similar among, and which are different? |
Gametogenesis and fertilization = similar mating = varies widely |
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Steps in fertilization |
1) Sperm and egg recognize each other 2) Activation of sperm 3) Plasma Membranes fuse (of sperm and egg) 4) Egg blocks entry of additional sperm (block polyspermy) 5) Egg is activated metabolically 6) Egg and Sperm nuclei fuse |
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Layers of egg - for sea urchins and humans |
Sea urchins Outer = Jelly coat Inner = Vitelline envelope Humans Outer = Cumulus Inner = Zona Pellucida |
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How is fertilization by the wrong species prevented |
Lock and Key mechanism Sperm binds to species specific receptors on inner layer of egg to prevent fertilization by wrong species In sea urchins: bindin molecules in accrosomal process bind to bindin receptors on egg's vitelline layer |
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Sperm anatomy (for sea urchins; similar for humans) |
Tail = allows it to swim Numerous Mitochondria = produce ATP so can swim Nucleus = haploid Centriole Acrosome = membrane enclosed structure on sperm head that contains enzymes and other proteins |
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Accrosomal Reaction - function |
Allows sperm to recognize and pass through protective layers of egg |
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Accosomal Rxn - steps (in sea urchins) |
1) Jelly coat releases substances attracting sperm 2) Contact - sperm makes contact with jelly coat, triggering accrosomal rxn 3) Accrosomal Membrane breaks down, releasing enzymes that digest through jelly coat 4) Growth of Accrosomal Process; polymerization of actin causes it to elongate and form accrosomal process which has bindin molecules = key to lock, bind to bindin receptors on egg's vitelline layerr 5) Formation of Fertilization cone - fusion of plasma membranes of sperm and egg; 6) Fertilization Cone draws sperm in: Entry of Sperm Organelles - contributes sperm nucleus and centriole; mitochondria degrade |
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What does the sperm contribute to the zygote? |
Centriole and sperm nucleus |
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Ployspermy |
Fertilization of egg by more than 1 sperm -don't want more than 2n = too many chromosomes (triploidy, etc.) |
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Types of Blocks to Polyspermy in Sea Urchins
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1) Fast Block = influx of Na+ ions 2) Slow Block = release of Ca2+ and fusion of corticol granules = corticol rxn (caused by releases of corticol granule contents) |
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Fast Block to Ployspermy in Sea Urchins |
-Influx of Na+ ions (after fusion of plasma membranes) --> depolarizes membrane, preventing fusion of other sperm within the membrane -occurs 1-3 sec after sperm/egg membrane fusion -lasts for about 1 minute |
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Slow block to polyspermy in sea urchins |
Corticol rxn: Series of changes in outer zone of egg cytoplasm to make egg impenetrable to sperm: 1- Sperm entry triggers release of Ca2+ (stored in endoplasmic reticulum of egg) 2 - causing Corticol Granules to fuse with plasma and release contents 3 - Corticol Granule contents block polyspermy: -enzymes dissolve bonds between vitelline envelope and plasma membrane -proteins cause water to rush in - causes swelling and formation of fertilization envelope (as vitelline layer is lifted off); fertilization envelope aids in resisting sperm entry -enzymes degrade sperm binding receptors as envelope hardens -enzymes cause envelope to harden |
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Which coat triggers accrosomal rxn in sea urchins? In humans? |
Sea Urchins = Outer Coat (Jelly Coat) Humans = Inner Coat (Zona Pellucida) |
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Cumulus |
Outer layer of egg -contains follicle cells in a gelatinous matrix -sperm just travels through (no accrosomal rxn) |
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Zona Pellucida |
Inner layer of egg -contains glycoproteins -triggers accrosomal rxn that digests path through zona pellucida (accrosomal rxn similar to that in sea urchins) |
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Blocks to polyspermy in Mammals vs in sea urchins |
- Don't have fast block - Still have slow-block --Sperm binding triggers increase in Ca2+ and cortical reaction -Don't have fertilization envelope --But sperm binding molecules ARE destroyed - functions as slow block to polyspermy |
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fertilization envelope |
Envelope that forms in sea urchins after enzymes from corticol granules cause water to rush in and vitelline layer to be lifted -aids in resisting sperm entry |
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Diocious Species
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Species that have separate male and female members |
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Monocious (or hermaphroditic species) - description and types |
Have a single individual that produces both sperm and egg (still a form of sexual reproduction). Two types: 1) Simultaneous: Male and Female at the same time -some species - must mate with another individual -other species - can self fertilize (still sexual reproduction 2) Sequential: Function as male or female at different times |
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Advantage of monecious species |
If individuals have low probability of finding mate |
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External Fertilization - description and what it requires |
Eggs shed by female and fertilized by male in environment (aka "spawning") -requires environment where eggs can develop without desiccation or heat stress (usually in water) |
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Features of external fertilization that ensure fertilization will occur |
-Release large numbers of gametes -release can be synchronized by day length, temperature, etc. -Sometimes get congregation of potential mates |
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Internal Fertilization |
Release of Sperm into female reproductive tract -need to keep egg moist & also a place where sperm can swim to egg -produce fewer zygotes compaired to external fertilization -provide more parental care of the young |
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Oviparous vs. Vivipourous Animals |
Oviparous = lay eggs that can withstand harsh environments (eggs provide more paternal care than external fertilization would) Viviparous = retain embryo, which develops in reproductive tract (provides much more parental care) |
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Complex reproductive systems that have evolved for internal fertilization |
Primary Sex Organs = Gonads Secondary Sex Organs = All additional components of reproductive system, including genitalia (external sex organs) Copulation = joining of female and male accessory sex organs |
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Male Primary Sex Organ |
Testes |
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Testicle |
Testis + Scrotum -testis is held externally to body in scrotum |
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Sperm travel (in males) |
remember SEVEN UP: 1) S: Sperm are produced in Seminiferous Tubules of Testis 2) E: Mature and Stored in Epididymis 3) V: Travel through Vas Deferns which goes behind bladder -seminal vesicle - links up and contributes vital fluids to semen 4) E: joining become Ejaculatory Duct -sperm passes through Prostate Gland and then Bulbourethral Duct Gland - both of which contribute vital fluids to semen 5) N: nothing 6) U: Ejaculatory duct links up with Urethra - and have common output for urinary and reproductive systems 7) P: Ejaculated through Penis (male copulatory organ) |
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Components of Semen |
1) sperm = less than 5% of semen 2) Fluids and molecules that support sperm + facilitate fertilization --> are secreted by 3 accessory glands (all are paired structures: (1) Seminal Fluid (seminal vesicles) ~60% of semen (2) Prostate Fluid (Prostate Glands) ~30% of semen (3) Alkaline Secretion (Bulbourethral Glands) small volume |
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Secretions by male sexual accessory glands |
1) Seminal Fluid (seminal vesicles): ~60% of semen -seminal vesicles empties into vas deferens -contributes fructose - nourishes sperm 2) Prostate Fluid (Prostate Gland): ~30% of semen -gives fluid alkaline properties - neutralizes acidity in male and female reproductive tracts 3) Alkaline Secretion from Bulbourethral Gland (in addition to that secreted by prostate gland): small volume -also neutralizes acidity in urethra -lubrication - facilitating sperm movement during climax |
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how sexual stimulation leads to sperm delivery (overview) |
-Sexual Stimulation produces penile erection - enabling penis to be inserted into vaginaW |
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What is human penis composed of |
Spongy erectile tissue derived from modified veins and capillaries |
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Steps from Sexual Arousal -> Erection |
1) Sexual Arousal -> Arousal triggers stimulation from CNS through ANS which causes (through its release of Nitric Oxide, NO): 2) Artery Dilation -> allows more blood to flow into spongy tissue 3) Veins are compressed as vascular compartments expand -> causing them to not be able to empty as much blood 4) Erectile Tissue becomes engorged with blood -> due to actions of arteries and veins; thus facilitating insertion into vagina |
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Erectile Dysfunction |
Inability to achieve an erection -Can be treated with drugs that promote vasodialation of the local regulator, Nitric Oxide (NO); -ex: Viagra |
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Steps of Semen Expulsion |
-After erection begins, semen is expelled through vas deferntia, ejaculatory duct, and urethra: 1) Semen Emission: Rhythmic Contractions of Glands & Ducts move semen into urethra at base of penis 2) Semen Ejaculation: Contractions by muscles at base of penis cause ejaculation: ejaculate = ~2-6ml of semen, with 50-130 million sperm per mL 3) Prostaglandins in semen stimulate Uterine Contractions ---> cause sperm to move up (only later do sperm swim!) 4) Anticoagulants liquify semen to liberate sperm - so can swim |
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Female primary sex organ |
2 ovaries |
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Egg travel in females |
(1) Starts in Ovary (2) Travels to Oviduct (aka fallopian tube) (3) Then to muscular Uterus (4) then base of uterus - the cervix, with small opening (5) Finally to the vagina |
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Primary Function(s) of male and female sex organs |
Male: (1) Produce and Deliver Sperm Female: (1) Produce Eggs (2) Receiving Sperm |
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Sperm Travel in females |
(1) Sperm is deposited into Vagina (2) Contractions propel sperm through Cervical Opening (3) Travels through Uterus (4) Finally ends in Oviduct - where fertilized |
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How eggs are released and move |
Ovaries contain many follicles - all follicles are formed at birth; Ovulation = release of an egg (from ovaries): -follicle cell bursts, releasing egg into oviduct - fimbria of oviduct collects egg and makes sure it travels to oviduct and not abdominal cavity -cilia propel egg towards uterus -neck of uterus is cervix which opens to vagina |
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follicle |
Functional unit of oveary ; One egg cell surrounded by follicle cells |
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Uterus |
thick muscular organ lined with endometrium and rich in blood vessels |
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where does gametogenesis occur? (What are gametes called?) |
In Gonads: males = testes (gametes = sperm) females = ovaries (gametes = ova) |
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How are gametes produced (broadly for men and women?) |
from Germ Cells = present in early development; migrate to gonads when gonads begin to form Germ cells undergo mitosis to produce stem cells: spermatogenesis and oogenesis --> self-regenerating stem cells that also produce spermocytes and oocytes Meiosis then produces haploid cells that mature into sperm and ova |
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Spermatogenesis = what it is and where it occurs |
Production of mature sperm cells Occurs in seminiferous tubules of testis -spermatagonia is located in periphery of each seminiferous tubule and developing cells move towards lumen |
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Process of Spermatogonia |
(1) Male Germ Cells (2n) = 1 **mitosis --> (2) Spermatagonium (2n) = 1 **mitosis --> (3) Primary Spermatocyte (2n) = 1 **first meiotic division --> (4) Secondary Spermatocyte (n) = 4 **second meiotic division --> (5) Spermatids (n) = 4 **growth and maturation --> (6) Spermatozoa (sperm) (n) = 4 |
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What types of cells (from spermatogenesis) are found in embryo? |
Male Germ Cells Spermatogonium |
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What types of cells (from spermatogenesis) are found in adults? |
Spermatogonium Primary Spermatocytes Secondary Spermatocytes Spermatids Spermatazoa |
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Oogenesis |
Production of Mature, unfertilized egg cells |
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Process of Oogenesis |
(1) Female Germ Cell (2n) = 1 **mitosis --> (2) Oogonium (2n) = 1 **mitosis --> (3) Primary Oocyte (2n) = 1 **arrested in meiosis prophase I until puberty **starting at puberty, first meiotic division--> (4) Secondary Oocyte (n) = 1 + 1 polar body **arrested until fertilization **after fertilization, second meiotic division--> (5) Ootid (n) = 1 + 2nd polar body (and 1st) **"growth/maturation" --> (6) Ovum (egg) (n) = 1 (polar bodies degrade) |
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Why get polar bodies during oogenesis |
During meiotic division, cytokinesis is unequal: -most of cytoplasm goes to one daughter cell -other cell becomes polar body |
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Cytoplasmic Bridges in Spermatogenesis |
Connect spermatids --> b/c have 2 X cells and 2 Y cells; Xs have some necessary proteins that Ys are missing; thus need the connection |
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gametogenesis in males vs femals |
(1) Asymmetry during cytokenesis of meiotic divisions of oogenesis: -get 1 product in oogenesis -get 4 products in spermatogenesis (2) Females have all the primary oocytes they'll ever have; Males sperm cells continue to develop throughout life (3) Oogenesis has long periods of arrested development Spermatogenesis is an uninterrupted process |
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Gonadotropin Relesaing Hormone (GnRH) |
Released by hypothalamus = key regulator of LH & FSH in Anterior Pituitary |
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What controls male sexual function? |
Hormones; |
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List the steps of increased production of testosterone beginning at puberty |
(1) Increased GnRH produced by hypothalamus, causes (2) Release of LH and FSH by Anterior Pituitary (3) **LH stimulates Leydig Cells to increase Testosterone --> Testosterone leads to increased growth rate and development of secondary sex characteristics **FSH and testosterone control sertoli cells - which control spermatogenesis (4) Negative Feedback Loops: **Sertoli Cells also produce inhibin which exerts negative feedback on Anterior Pituitary **Testosterone can exert negative feedback on hypothalamus and anterior pituitary |
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The Linked cycles in females, and what they do |
Ovarian Cycle = produces egg and hormones Menstrual Cycle = prepares endometrium for embryo |
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Ovarian Cycle - features |
-Woman only has so many: born with ~1 million primary oocytes in each ovary, most degenerate, but a woman will go through ~450 ovarian cycles -At menopause (end of fertility) may only be a few oocytes left --> ovaries lose responsiveness to gonadotropins as well, thus resulting in a decline of estrogen producton |
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Phases of Ovarian Cycle |
(1) Follicular Phase: follicular cells produce estrogen and progesterone -usually one follicle matures completely - releasing egg midcycle (2) Luteal Phase: Follicle cells left in ovary develop into endocrine gland = corpus luteum -CL produces estrogen and progesterone for ~2 weeks -CL degenerates if no fertilization |
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Menstrual cycle - features |
Prepares environment for fertilized egg -parallels ovarian cycle -consists of buildup and breakdown of endometrium: ---endometrium thickens in preparation of embryo (in max state of preparedness for ~9 days) ---if no embryo, sloughing off of endomentrium = menstruation -human menstrual cycle ~28 days -human females = receptive to sexual activity throughout their cycles ---unlike most mammals which go into estrus (when receptive; around ovulation) |
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Basic Pathway for release of Estrogen and Progesterone by Follicles and CL |
(1) Hypothalamus secretes GnRH (2) AP secretes LH and FSH (3) Ovary - follicles and CL secrete Estrogen and Progesterone (4) Estrogen and progesterone travel to uterus; Also provide feedback: **Estrogen = positive AND negative feedback to hypothalamus and AP **Progesterone = negative feedback to hypothalamus and AP |
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hormonal control of Menstrual and Ovarian Cycles |
(1) Pre-menstrual: high FSH and high LH **stiumlates: (2) Follicle Growth in ovaries **causes: (3) Increased production of estrogen by maturing oocytes **causes (positive feedback): (4) Surge of LH and FSH **causes: (5) Ovulation and development of Corpus Luteum **leads to (6) CL secretes Estrogen and Progesterone - so levels rise **stimulating (7) Development of endometrium (in preparation for pregnancy) **eventually, if not pregnant: (8) Corpus Luteum degenerates **causing (9) Decrease in Estrogen and Progesterone **causing (negative feedback): (10) LH and FSH levels rise --> back to step 1 |
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When can pregnancy occur?
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Over a 5-7 day window around ovulation --ovulation occurs around day 14 of ovarian/menstrual cycle B/c: (1) egg hangs around in oviduct for ~24/48 hours (2) sperm can live in female reproductive tract for ~ 5-7 days |
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Fertilization - where occurs, and basics on what is happening (and what is formed) |
Sperm must reach egg in upper oviduct in order to fertilize fertilization stimulates secondary oocyte to complete secondary meiotic division fertilization results in fusion of haploid sperm and egg nuclei to form diploid zygote -undergoes cell division and becomes blastocyst --blastocyst implants in endometrium |
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Pregnancy Length in humans |
266 days/9 months -3 trimesters |
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formation of placenta |
tissues from growing blastocyst and endometrium develop into placenta
-blood vessels in umbilical cord carry nutrients and oxygen from mother to fetus and carry waste away ---vein = caries in oxygenated blood ---artery = carries blood with waste away |
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Changes in Ovarian Cycle during pregnancy |
Changes in mother cause it to cease: ----> High levels of estrogen and progesterone prevent pituitary from secreting gonadotropins. Get high levels as such: -After fertilization and implantation: --layer of cells covering blastocyst secrete human chorionic gonadotropin (hCG) ---hCH stimulates CL to produce estrogen and progesterone to prevent menstruation and maintain endometrium --after CL degenerates (~2nd trimester) -> placenta becomes main producer of estrogen and progesterone |
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first trimester basics |
main period of organogenesis -heart beats and limbs form by end of week 8 all major adult structures are present in rudimentary form = now known as a fetus Period when most susceptible from damage from drugs/chemicals (because fetus is rapidly developing) |
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Second trimester basics |
Limbs elongate - fingers, toes, facial features form fetal movement is felt by motherT |
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Third trimester basics |
Internal organs mature Kidneys can now excrete urine Brain goes through sleep wake cycles Birth occurs when lungs are mature |
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Stages of Labor |
(1) Dilation of cervix (2) Expulsion: delivery of infant (3) Delivery of placenta |
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Main process that enables childbirth to occur |
Strong rhythmic contractions -triggered by hormonal and mechanical stimuli |
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Cause of contractions during birth |
(1) Increased ratio of estrogen (stimulates contractions) to progesterone (inhibits contractions by increasing activity of oxytocin receptors on uterine wall) by end of 3rd trimester (2) Fetus pushes more on cervix (3) Release more oxytocin (4) Stimulating more contractions (5) Causing more dilation of cervix (first stage of labor) |
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Failure proof methods for preventing pregnancy |
(1) Abstinence (2) Surgical Removal of Gonads |
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Contraception |
Prevent fertilization of implantation |
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Abortion |
Termination of pregnancy after fertilized egg has implanted. Two types: Spontaneous Abortions: miscarriage Medical Intervention |
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Reproductive technologies |
Artificial Insemination: Sperm placed in female reproductive tract Assisted Reproductive Technologies: Unfertilized eggs are removed from ovary, combined with sperm outside body, and replaced in female (ex IVF) |
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Why don't have hormonal contraception for men? |
Blocks testosterone --> unwanted consequences (decreased sex drive/feminizing) |
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genitalia |
external sex organs |
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leydig cells |
produce testosterone; in testicles |
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Sertoli Cells |
In testicles; enable spermatogenesis also produce inhibin (exerts negative feedback on FSH production) |
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Development |
Process in which a multicellular organism undergoes a series of progressive changes that characterizes its life cycle |
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Stages of development in embryos: |
1. Determination = fate of cell is set 2. Differentiation = becoming specialized in structure and function (i.e., actually becoming cell determined to be) 3. Morhpogenesis = organization and spatial distribution of differentiated cells (includes organ development) 4. Growth = increase in body size by cell division and cell enlargement |
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Cell fate |
which type of tissue the cell will eventually become |
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What influences cell fate determination |
differential gene expression and extracellular environment |
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determination vs differentiation |
determination = a commitment differentiation = actualization of commitment |
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Cell potency |
Potential to differentiate into other cell types (declines with development) |
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Greatest level of potency cells to least |
Greatest (1) Totipotent (2) Pluripotent (3) Multipotent (4) Unipotent Least |
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Totipotent |
Can differentiate into any cell -early embryo |
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Pluripotent |
Can differentiate into most cell types - but can't form new embryo -late stage embryo |
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Multipotent |
Can differentiate into several related cell types -Late developmental stages and into adulthood |
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Hematopoetic Stem Cells - what is and potency |
Stem cell that gives rise to other blood cells -Multipotent |
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Unipotent |
Can differentiate into once cell type -mature organism |
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Two ways cell fate is determined: |
(1) Cytoplasmic Segregation (2) Induction |
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Cytoplasmic Segregation |
Unequal Cytokinesis -- helps determine cell fate |
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How does cytoplasmic segregation help determine cell fate |
-Determines Polarity - causing Cytoplasmic Determinants to be distributed unequally in egg cytoplasm: -Cytoplasmic Determinant distribution directs embryonic development -cytoskeleton contributes to this asymmetrical distribution of determinants: ---microtubules have polarity (grow in + direction only) ---cytoskeletal elements can bind motor protein elements which transport determinants to one side of cell or other |
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polarity |
the difference between one end of the organism and the other -develops early in development -yolk and other factors are distributed asymmetrically --> get two poles: Animal Pole and Vegetal Pole |
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Experiments that show that animal and vegetal poles can differ in developmental potential - thus helping determine cell fate |
Take 8 cell stage sea urchin embryo - dissect two ways and get different results --> (A) Let animal and vegetal poles develop separately --> get undeveloped cells on top and abnormal larva on bottom (B) Dissect L-R so have some of each pole in both sections --> both halves develop into small but normal larvae |
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cytoplasmic determinants |
Can be specific proteins, small regulatory RNAs and mRNAs Help direct cytoplasmic segregation which determines polarity and cell fate |
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induction |
cells in development embryo influence one another's developmental fate via chemical signals known as inducers and signal transduction mechanisms |
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How do inducers control activation of genes |
through signal transduction cascades: -most inducers are proteins (or growth factors) so have receptors on cell surface: when bind, goes through signal transduction phase in order to effect cell -differential gene expression leads to cell differentiation |
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Pannexin Proteins: are only found in the brain; In a liver cell, what would you find of Pannexin? |
Pannexin Gene But NOT pannexin mRNA or Pannexin Protein |
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how do inducers affect transcription? |
inducer molecules go mostly to cell closest to it -concentration of inducer affects degree to which transcritption factor is activated --if high enough, transcription factor will enter nucleus and stimulate gene expression involved in cell differentiation |
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What does fusion of sperm and egg plasma membranes accomplish? |
-Produces 2n zygote -Stimulates ion fluxes across egg membrane -blocks polyspermy -changes pH of egg cytoplasm (expels H+) -increases egg metabolism and DNA/Protein Synthesis -initiates cell division = first steps of development |
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contributions to zygote from egg and sperm |
Egg: -haploid nucleus -cytoplasm = rich in organelles, nutrients, and cytoplasmic determinants -mitochondria (with DNA) Sperm: -haploid nucleus -centriole -> becomes centrosome, which organizes mitotic spindles for cell division |
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Hemispheres of Frog Zygote |
Vegetal Hemisphere = lower half, where yolk granules (nutrients) are concentrated Animal Hemisphere = upper half, highly pigmented, contains haploid nucleus |
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rearrangement of egg cytoplasm in frogs post - summary of what is happening |
Sperm entry establishes polarity in zygote -information molecules are thus not divided evenly among daughter cells |
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rearrangement of egg cytoplasm in frogs post - detail of process |
(1) Sperm Enters in animal hemisphere; causing (2) Rotation of Outer Cortical Cytoplasm towards site of entry -causing shift in animal and vegetal poles - start to connect, causing (3) Gray Crescent forms = band of pigmented cytoplasm opposite sperm entry (becomes future dorsal side of tadpole) -formation relies on centriole -important for specifying body axis -key organizational roles in development embryo |
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How does cytoplamic rearrangement change distribution of critical developmental signals? |
Centriole (from sperm) initiates cytoplasmic reorganization: (1) Causes microtubules in vegetal hemisphere to form a parallel array to guide movement of cortical cytoplasm ---> formation of gray crescent (2) As cytoplasm moves, key developmental signals are distributed -ex: Beta Catenin transciption factor produced by maternal mRNA |
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Successive Stages following Fertilization |
(1) Cleavage = to create multicellular embryo (embryo called blastula) (2) Gastrulation = to produce 3-layered embryo (embryo called gastrula) (3) Organogenesis = forming organs |
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Cleavage |
Early cell divisions with NO cell growth -embryo becomes a solid ball of small cells |
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Embryo called after blastocoel forms |
blastula |
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blastocoel |
central fluid-filled cavity that forms in middle of balls of cells during cleavage |
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blastomeres |
cells of blastula |
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patterns of cleavage depend on |
amounts of yolk -- which depends on how much embryo needs nutrients from egg |
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Types of cleavage |
Complete Incomplete-Discoidal Incomplete-Superficial |
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Complete Cleavage |
Completely cleaves through zygotes -in mammals, frogs, sea urchins, etc. -blastomeres similar in size (except in frogs - vegetal pole has more yolk, so unequal division - daughter cells in animal pole are smaller) |
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incomplete - discoidal cleavage |
Embryo forms a blastodisc on top of yolk; cleavage doesn't penetrate yolk -occurs in eggs with lots of yolk (birds, fish, etc.) |
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Incomplete - Superficial Cleavage |
Mitosis without cell division -get many nuclei, known as syncytium: single cell with many nuclei. -The many nuclei move to periphery and plasma membrane grows inwards around nuclei -End result = blastoderm -Occurs in Insects |
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how do cytoplasmic determinants determine planes of cleavage and arrangement of blastomere |
cytoplasmic determinants determine position of mitotic spindles -orientation of mitotic spindles is important for planes of cleavage and arrangement of blastomeres |
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types of cleavage based on arrangement of mitotic spindles |
(1) Radial Cleavage = mitotic spindles form parallel or perpendicular to animal-vegetal axis (2) Spiral Cleavage = Mitotic spindles form at oblique angles to animal-vegetal axis (3) Rotational Cleavage = (in mammals) -First division: Parallel to A-P axis, yields to blastomeres -Second division: involves 2 planes at right angles to each other (and to the first plane) |
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Features of cleavage in mammals |
-Complete & Rotational -Slow & Asynchronous -Transcriptional changes play role (b/c so slow) |
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Features of Cell division during cleavage in mammals |
-Early Divisions = loosely associated ball of cells -8 cell stage = blastomeres change shape and maximize contact with one another to form tight ball (no blastocoel) -32 cell stage = cells separate into 2 groups: *inner cell mass = becomes embryo *Trohpoblast = Sac that forms from outer cells; helps to make blastocoel by secreting fluid -After 32 stage, embryo is calld a BLASTOCYST (not a blastula) |
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Where do fertilization and cleavage occur? |
Fertilization = in oviduct Cleavage = as zygote travels down oviduct to uterus |
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when does human zygote hatch out of zona pellucida |
when reaches Uterus |
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What prevents early implantation of the egg? |
Zona Pellucida |
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When does implantation of the egg occur? |
When troophoblast adheres to endometrium in a specific uterine section (and is aided by adhesion molecules and enzymes) -anywhere else leads to ectopic pregnancy ---trophoblast wants to make contact with maternal blood, so can lead to hemorrhaging |
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Fate Maps |
Produced by labeling blastomeres to identify the tissues and organs they generate |
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Mosaic Development vs. Regulative Development - what decides the type |
Depends on when become "determined" -Mosaic development = early determination - each blastomere contributes certain aspects to adult mammal *remove 1 blastomere and portion of embryo won't form -Regulative Development = late determination = other cells will compensate for any lost cells |
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Key concept behind why twins form |
Regulative development --- if blastomeres separate into 2 groups, each can become an embryo |
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Twin Types |
Monozygotic = identical twins from same zygote -depending on when blastomeres split, can have own or shared placenta Non-Identical Twins = 2 eggs fertilized by 2 sperm Conjoined = inner cell mass starts to split but doesn't split all the way Parasitic Twins = inner cell mass starts splitting but doesn't split all the way -one side develops normally, other side doesn't and is absorbed by normal side |
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Potency and Monozygotic Twins |
Shared Placenta = broke off when pluripotent Two placenta = broke off when totipotent |
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gastrulation |
massive movements of cells transform blastula into an embryo with 3 tissue layers and distinct body axes |
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Germ Layers |
(1) Endoerm = innermost layer -becomes lining of 2 tubules - respiratory and digestive -also becomes out growth of tubes - pancreas, thyroid, liver, and lungs (2) Ectoderm = outermost layer -nervous system, eyes, ears, and skin (3) Mesoderm = middle layer -contributes to tissue in many organs: heart, blood vessels, muscle, and bone |
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What does gastrulation begin with? |
Changes in shapes of blastomere and slowing of mitosis |
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Types of cell movement during gastrulation |
(1) Invagination = infolding of sheet of cells into embryo (2) Involution = cells rolling over the edge of a lip into interior (3) Epiboly = cells moving over surface of embryo towards site of involution |
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At end of gastrulation - |
-embryo has 3 germ layers -dorsal-ventral and Anterior-Posterior organization -fates of specific regions have been determined |
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Gastrulation in sea urchins - steps |
(1) Vegetal Hemisphere flattens as cells change shape (2) Vegetal pole cells migrate into cavity and become primary mesenchyme (cell layers of mesoderm) (3) Vegetal pole invaginates - cells form archenteron which is pulled inward by secondary mesenchyme which have filapodia that attach to ectoderm (4) Finally, make contact with archeneron + ectodermal cells on top. Opening = blastopore and becomes anus (other end, end of contact, eventually pinches off to form mouth) |
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Archenteron |
Primative Gut |
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Filapodia |
On Secendary mesenchyme of sea urchin; during gastrulation attach archenteron and ectodermal cells on top |
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Gastrulation in the frog - steps |
(1) Bottle Cells form in gray crescent area and elongate and move to form dorsal lip of blastopore (2) Cells start moving over lip and involute into the interior - to form mesoderm and endoderm layers (3) Blastopore Lip surrounds a "pug" of yolk rich cells; another set of bottle cells form and involution causes archenteron & destroys bloastocoel |
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Hans Spemann Experiments - result |
Reveals how determination occurs |
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Hans Spemann Experiments - details of each |
Experiment 1: Bisected salamander two ways with different results (1) bisected gray crescent -> two normal larvae produced (2) Gray crescent on one side only -> normal developed on side of gray crescent, belly piece developed on other side ----> Conclusion: cytoplasmic factors, such as those in gray crescent, are necessary for normal development Experiment 2: Transplant (of what should be neural ectoderm to where epidermis should form) in salamander eggs at different stages: (1) early gastrula -> epidermis did form (2) late gastrula -> second neural plate formed instead --> Conclusion: cell fate is determined during gastrulation Experiment 3: Placed part of dorsal lip in area that should make epidermis -had second site of gastrulation -> got 2 salamanders --> conclusion: since blastopore dorsal lip could induce host tissue to form an entire embryo, called the dorsal lip the primary embryonic organizer |
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Primary embryonic organizer in frogs |
Dorsal Lip |
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How does the dorsal lip in frogs result in body organization? |
Involutes during gastrulation - thus guiding formation of head, trunk, etc.: -produces specific growth factor antagonists at different times to achieve different patterns of differentiation on A-P axis ---by interacting with growth factors in adjacent cells (inhibiting or activating), since involuting, changing adjacent cells |
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Gastrulation in Reptiles and Birds (and basically mammals) - Steps |
(1) Start with blastodisc: flat disc of cells on top of the yolk --arranged in two layers: hypoblast (lower, will contribute to extraembryonic membrane) and epiblast (upper, will become embryo) (2) Epiplast cells move towards midline, forming ridge - known as primative streak - continue moving until streak fully formed in midline |
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Primative Streak - features |
Primative Groove = in middle, where cells migrate through to become endoderm and mesoder -functions as blastopore Hensen's Node = most anterior of streak, primary organizer -equivalent to dorsal lip in amphibians -in reptiles, birds, mammals |
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Inner cell mass in mammals |
Two layers: hypoblast = lower layer - contributes to extraembryonic membranes that surround embryo and helps form placenta epiblast = upper layer - forms embryo -upper layer forms amnion - surrounds embryo and is filled with amniotic fluid |
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What helps determine left right symmetry in mammals? |
Cilia at top of Primative Groove which beat to create asymmetrical flow of extracellular fluid |
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features of gastrulation in placental mammals |
-Very similar to with reptiles -Have inner cell mass with the two layers (hypoblast and epiblast) -have a primative groove -have Hensen's Node = primary organizer |
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Organogenesis |
Organ and Organ Systems form - cells from different germ layers participate in formation of single organ |
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neurulation |
one part of organogenesis (occurs early in organogenesis): initiation of the nervous system |
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chordamesoderm |
mesoderm closest to midline; prodces notochord -has organizer functions and induces overlying ectoderm to form nervous system |
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notochord |
= rod of mesoderm that provides support for embryo (not present in adults, is replaced by vertebral columns in ectoderm)
-produced by chordamesoderm |
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Steps in neurulation |
(1) Chordamesoderm produces Notochord (2) Ectoderm lying over notochord thickens to form Neural Plate (3) Edges of Neural plate fold and a deep groove forms (4) Folds fuse - forming Neural Tub and layer of epidermal ectoderm (5) Neural Crest Cells dissociate from neural tube and migrate outward; leading development of connections between CNS and rest of body |
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Failure of neural tube to form |
At Anterior End = Brain -Anencephaly (no forebrain develops) Rest = spinal cord At Posterior End -Spina Bifida |
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when does body segmentation occur |
during neurulation |
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somites |
body segments; form from mesoderm on either side of neural tube -produce cells that become vertebrae, ribs, muscles, limbs, and lower skin layer -guide neural crest cells in peripheral nerve development |
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homeotic genes |
genes that control body segmentation -all have a DNA sequence called the homeobox which encodes the homeodomain responsible for DNA binding |
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Hox Genes |
Homeotic Genes for vertebrates -> control differentiation along A-P axis -are expressed along A-P axis of embryo in same order as their arrangement between the 3' and 5' ends of the gene complex on the chromosome -different segments of embryo receive different combinations of gene products |
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Positional Information |
Molecular cues that control pattern formation |
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morphogens |
inducer that provides positional information |
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Ex of a morphogen |
Morphogen Sonic Hedgehog (Shh) - produced by Zone of Polarizing Activity; -makes an Shh gradient that determines A-P axis ---cells exposed to a higher dose of Shh (closest to ZPA) = little finger forms ---cells exposed to lower dose of Shh (further from ZPA) = thumb forms (hox genes also play role in this) |
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how dorsal-ventral information is obtained |
genes provide d-v information: -tissues in each body segment different based on dorsal-ventral position |
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functions of morphogenesis |
-cell differentiation -cell division -ALSO Apoptosis |
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potency of a zygote; what occurs during development |
Totipotent -> as development proceeds, cells become determined and lose their totipotency **but, most differtentiated cells still contain the entire genome and still have the genetic capacity for totipotency |
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Example of Nuclear Transfer |
Animal Cloning: Dolly the sheep - (1) Take udder cell (somatic differentiated cell) and remove nucleus --> becomes donor nucleus (2) take an egg from a different sheep and also remove the nucleus --> becomes host sheep (3) Take donor nucleus and place in egg from host sheep and then place the egg back into the host sheep --> Clone develops in host -no genetic information is lost as cell passes through developmental stages -cytoplasmic environment can modify cell fate |
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Stem Cells |
Rapidly dividing undifferentiated cells that can differentiate into several cell types |
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Stem Cells in adults - potency |
Multipotent |
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Stem cells in embryonic blastocyst |
Embryonic Stem Cells = pluripotent -can be harvested from human embryos |
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Problems with embryonic Stem Cells |
(1) Ethical issues (2) Could have immune response - rejection |
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Induced Pluripotent Stem Cells (iPS Cells) |
Made from differentiated cell in vitro by the addition of several genes essential for undifferentiated state |
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heterotrophs vs autotrophs |
heterotrophs = derive nutrition from eating other organisms autotrophs = use solar or inorganic chemical enrgy to synthesize its own organic molecules all animals are heterotrophs, but all get nutrition (either directly or indirectly) from autotrophs |
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Diet supplies what 3 nutritional needs |
(1) Chemical Energy for cellular processes -fuel that allows cellular processes to work (2) Organic Raw Materials used for Biosynthesis -come in form of carbon skeletons, which can be used by body to make most molecules in body (3) Essential Nutrients -raw materials from carbon skeletons aren't enough to make all molecules we need, so need to get some materials pre-assembled = essential nutrients |
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Food energy conversion to biological work |
Follows first law of thermodynamics (energy can't be destroyed or created, must be converted) -mammals balance energy in (fat, protein, and carbohydrates) with energy out (metabolic processes and exercise) |
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All energy needs are met by _____. Explain |
Food. Breakdown organic molecules to release energy to perform biological work |
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Kilocalorie |
unit for energy in nutrition 1 kcal - 1,000 calories = 1 Calorie (Cal) 1 cal = amount of heat needed to raise 1 gram of water 1 degree Celsius |
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components of food are broken into ______________. How much energy each provide |
Protein: 4.1 Cal/gram Carbs: 4.2 Cal/gram Fats: 9.5 Cal/gram <--- most energy per gram! |
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Basal Energy Requirement - definition; amount for human adult male and female |
Amount of energy to just perform basic activities to live Male = 1600-1800 Cal/day Female = 1300-1500 Cal/day |
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How is food stored: |
Carbohydrates ---> -stored in liver and muscle as glycogen -meets about 1 day's energy reserves Fats ----> -stored with little associated water, more compact (ex: in adipose tissue) -most important form of stored energy (b/c more energy per gram) Proteins ---> -NOT used for storage but can be metabolized as last resort |
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Chronic Deficit of Calories leads to... |
Starvation: metabolism of body's own molecules begins: - first, glycogen and fat are broken down -finally proteins are metabolized: ---muscles decrease - start to lose kidney function ---eventually results in death - loss of heart, liver, or kidney function |
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Chronic Excess of Calories leads to... |
Obesity: Excess stored as increased body mass -first, glycogen stores build -then excess carbs, fats, and proteins are converted to body fat (first, subcutaneous fat under skin, then body fat goes to ectopic ares such as liver -can lead to increased health risks: ---type 2 diabetes, cardiovascular disease, and some cancers ---reduced life expectancy |
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Measure obesity |
Using BMI = Weight (kg) / Height (m^2) Normal = 18.5 - 24.9 Overweight = 26-29 Obese = 30-40 Morbidly Obese = 40+ |
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Carbon Skeletons |
building blocks for larger organic molecules animals require organic molecules to supply them. |
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Example of a carbon skeleton |
Acetyl Group --- is used to build more complex groups -must obtain acetyl group from food |
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In addition to an organic source of carbon skeletons, also need a source of organic ______, usually from _____ |
Nitrogen; usually in amino acids from digestion of proteins |
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Essential Nutrients = Molecules that ______ |
must be obtained in pre-assembled form |
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What are the classes of essential nutrients that food must supply |
(1) Essential Amino Acids (2) Essential Fatty Acids (3) Minerals (4) Vitamins |
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How many amino acids do animals require? |
20; but different animals can synthesize different amino acids |
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Essential Amino Acids |
Amino Acids that a particular animal cannot synthesize |
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How many essential amino acids must human adults obtain from food |
8 |
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What type(s) of food will give humans all 8 essential amino acids at once |
Animal Proteins |
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Complementary Diet |
Of Plant foods; eating food together that supply all 8 essential amino acids -since most plant proteins are incomplete (and must get all 8 around the same time -ex: grains and legumes |
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Essential Fatty Acids |
Certain unsaturated fatty acids that animals can't synthesize (have difficulty making double bonds in some fatty acids) |
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Example of an essential fatty acid |
Linoleic Acid = helps synthesize other unsaturated fatty acids, including signaling molecules and membrane phospholipids |
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Minerals |
the inorganic required nutrients Macronutrients and micronutrients |
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types of minerals; examples |
Macronutrients = mineral elements required in large amounts (ex: Ca2+ b/c of high turnover) Micronutrients = mineral elements required in small amounts (ex: Iron, Iodide) |
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Vitamins |
carbon compounds required for growth and metabolism that cannot be synthesized; (most function as coenzymes or parts of coenzymes) |
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How many vitamins do humans require |
13 |
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Two types of Vitamins |
Water soluble - including B and C -excreted in urine if there's excess Fat Soluble - AEDK -can accumulate to toxic levels in body fat and liver |
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Vitamin D - hormone or vitamin? |
both! Starts as prohormone Califerol -if don't get enough skin exposure, body can't synthesize it from skin so need it (thus a vitamin) |
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Nutrient Deficiencies can lead to _____; chronic ____ can lead to _____ |
Malnutrition Chronic Malnutrition can lead to deficiency diseases |
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Deficiency Diseases: -Causes -Results |
Scurvy (lack Vit D) = bleed easily, poor wound healing Beriberi (lack Vit B1) = extreme weakness Hypothyroidism (lack Iodine) Pernicious Anemia (lack Vit B 12) |
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Classifications of animals based on diet |
Herbivores = prey on plants Carnivores = prey on animals Omnivores = prey on plants and animals |
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Type of teeth an animal has is called _____ and it reflects ____ |
Dentition, diet |
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Tooth layers |
Enamel = composed of calcium phosphate, covers crown Dentine = bony material in crown and root Pulp Cavity = contains blood vessels, nerves, and dentine producing cells |
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Dentiton by animal type |
Herbivores = -large molars and premolars (to grind) -modified incisors and canine (for biting off pieces) Carnivores = -enlarged canine teeth (killing prey and ripping flesh) Omnivores = -multipurpose set of teeth |
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GI Tract also called |
Alimentary canal |
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Functions of GI System |
Motility = moving food mouth -> anus Digestion = mechanical (fragmenting food) and chemical Secretion = of enzymes to break down food Absorption = to get food/nutrients into body |
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When is food truly "inside" your body |
Only after absorption |
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what breaks down macromolecules in GI system (i.e., chemical digestion) |
hydrolytic enzymes which cleave bonds by hydrolysis |
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Hydrolytic enzymes which cleave bonds by hydrolysis (i.e., chemical digestion) - enzyme name and bonds broken |
Proteases: Break bonds between adjacent amino acids and proteins Carbohydrates: hydrolyze carbohydrates Peptidases: hydrolyze small peptides Lipases: hydrolyze fats to get fatty acids and glucose Nucleases: hydrolyze nucleic acids to get component nucleotides |
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What prevent GI Tract (enzymes) from destroying itself? |
1) Zymogens: digestive enzymes are produced in inactive form, known as zymogens -must be activated by another enzyme within GI tract lumen -can't act on cells that produce it 2) Mucus: cells lining gut are protected from enzymes by mucus |
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Key Aspects of Human GI Tract (Organs Beginning to End) |
1) Oral Cavity: Tongue, mouth, teeth 2) Esophagus 3) Stomach 4) Small Intestine: -Duodenum -Jejunum -Ileum 5) Large Intestine/Colon: -Ascending Colon -Transverse Colon -Descending Colon 6) Rectum 7) Anus |
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Tissue layers of the gut |
Lumen = gut cavity -inner layer, exposed to outside Mucosa = lines gut cavity -layer of epithelial cells -may secrete mucus, digestive enzymes, or hormones (depending on location -may aid in digestion Submucosa = Layer right under mucosa -contains blood and lymph vessels and nerves 2 Layers of Smooth Muscle: Circular Muscle Longitudinal Muscle |
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what initiates swallowing |
Food is chewed and tongue pushes bolus to soft palate |
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swallowing: propels food through ____ into ____ |
through Pharynx into Esophagus |
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enteric nervous system |
nerve nets in submucosa and between smooth muscle (in GI Tract) -only forms synapses with other nerves in network -like a second brain - mostly autonomous (although CNS can influence ststem small amount) -responsible for communication within GI Tract |
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what allows food to enter the esophagus |
upper esophageal sphincter |
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peristalsis |
waves of muscle contractions in esophagus that move food towards stomac |
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what type of muscle is the esophagus |
Skeletal in upper esophagus (voluntary aspects of swallowing) Rest is smooth - involuntary |
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How are muscles coordinated in esophagus? |
by Enteric Nervous System: -circulatory muscles contract and then longitudinal muscles contract then circulatory muscles contract again to force food forward; followed by waves of relaxation -as food moves resulting stretch causes next region to contract |
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_________ prevents food from moving backward into esophagus. _________ cause this to relax |
Lower esophageal sphincter = ring of circular smooth muscle -waves of peristalsis cause it to relax |
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how does food move in stomach and small intestines? |
Not as coordinated as in Esophagus -segmentation movements: segments of gut periodically contract but DON'T generate a wave of contraction that moves in one direction ---> allows food to move back and forth and mix with digestive juices -although do have some peristalsis to keep food moving down |
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where does chemical digestion begin; how? |
in the mouth: salivary glands secrete amylase that breaks down carbohydrates |
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How does chemical digestion occur in stomach? |
Gastric Pits: in stomach, have 3 types of secretory cells (which aid in digestion)- 1) Chief Cells 2) Parietal Cells 3) Epithelial cells that secrete mucus, which protects tissues from the acids and enzymes (against self-digestion) |
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Chief Cells |
In Gastric Pit of stomach -secrete Pepsinogen = zymogen of the protease pepsin (which begins protein digested when activated) |
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Pepsin: Purpose, and activation |
Begins protein digestion -Low pH in stomach converts inactive pepsinogen to pepsin -pepsin activates other pepsinogen molecules through autoacatalysis (positive feedback) |
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Parietal cells |
Secrete HCL which keeps pH ~2 by maintaining H+ concentration difference |
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How do Parietal cells maintain H+ concentration differences? |
--In the cell: Carbonic Anhydrase catalyzes formation of carbonic acid which dissociates into H+ and bicarbonate *an antiporter activaley transports bicarbonate out of cell into blood cell and Cl- into parietal cell from blood cell *another antiporter actively transports H+ into lumen (from Parietal cell) in exchange for K+ ions --K+ will leak out of cell (down gradient) into lumen, causing it to keep being pumped out - causing H+ to continually return to lumen --Cl- will additionally leak out into lumen from parietal cell - thus allowing HCl in lumen ----> thus the low pH (which helps activate pepsinogen, and also helps denature proteins) |
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Chyme |
Mixture of gastric juices and partly digested food in the stomach |
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how does chyme move through stomach |
stomach walls contract to move chyme to bottom of stomach |
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Pyloric Sphincter |
Allows small amounts of chyme to enter the small intestine at a time |
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Main function of liver |
synthesizes bile salts (from cholesterol) and secretes them as bile which flows through hepatic duct to duodenum |
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Gallbladder |
Site of bile storage |
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How is the gallbladder stimulated to release bile |
-Fats enter duodenum and signal epithelial cells to release the hormone Cholecystokinin (CKK) -CKK stimulates walls of gallbladder to contract rhythmically and squeeze bile into duodenum |
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How do Bile Salts emulsify fats in chyme |
-Have 1 lipophilic end and one hydrophilic end --Lipophilic ends merge with fat droplets to keep them from sticking together, thus breaking them down into micelles -this increases the surface area exposed to lipases (which digest fat); and also makes the outside hydrophilic |
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Pancreas main (exocrine) functions: |
function as both exocrine function and endocrine gland -Exocrine functions = secrete digestive enzymes to duodenum via pancreatic duct |
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What are some of the main exocrine enzymes secreted by pancreas |
Tripsinogen = protease zymogen -activated in duodenum by enterokinase to produce trypsin protease (which activates other zymogens) Bicarbonate = neutralizes chyme in intestine (b/c other proteases work better and more neutral pHs) |
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where do you finally get monomers in GI Tract |
small intestine |
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Where does most chemical digestion occur in the GI tract |
Small intestine; particularly the duodenum |
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Parts of the small intestine; main functions |
Duodenum = most digestion occurs here Jejunum and ileum = carry out most absorption |
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How digestion occurs in the small intestine |
epithelial cells secrete various enzymes which cleave peptides, disaccharides, and lipids : larger molecules --> monomers (which are then absorbed) |
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Two prime functions of small intestine |
digestion and absorption |
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anatomical features of small intestine that aid in digestion |
Increased Surface Area -has many folds with finger like projections, villi -villi have smaller projections: microvilli which give intestine enormous surface area for absorbing nutrients |
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How does absorption occur in small intestine (of everything except fat: nucleic acids, proteins, and carbohydrates)? |
(1) Nutrients are transported across epithelial cells - actively or passively. (2) From epithelial cells, move into the intestinal capillaries: (3) Capillaries/Veins -> Hepatic Portal Vein carries nutrient-rich blood to liver (4) from liver, blood travels to heart, etc. |
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How are nutrients (excluding fat) absorbed by small intestines? |
Either actively or passively: -Diffusion -Facilitated Diffusion --> ex: fructose (moves down concentration gradient) -Osmosis ---> ex: water -Active Transport ---> ex: inorganic molecules -Co-Transport ---> Symporters combine transport of nutrient molecules with Na+ |
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How are fats/lipids absorbed in small intestine? |
(1) Bile Salts emulsify fats into Micelles in the small intestine (2) Lipases work on micelles - convert to Fatty Acids and Monoglycerides (lipid soluble) (3) FA and Monoglycerides pass through microvilli membranes (b/c lipid soluble) (4) In cell, FA and monoglycerides are reformed into Chylomicrons = TG and cholesterol coated with proteins (water soluble) (5) Chylomicrons pass into lacteals = vessels of lymph system (6) Lymph eventually drains from lymphatic system into large veins which return blood to the heart |
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Main function of large intestine |
Absorbs (most) water and ions, and produces feces |
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feces |
semi-solid mass of waste products |
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too much or too little water absorption by large intestine causes |
too much = constipation too little = diarrhea |
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how is feces eliminated? |
Through anus, which consists of 2 sphincters: internal sphincter = under involuntary control external sphincter = under voluntary control |
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Explain mutualistic adaptations in GI Tract |
Microbiome provide nutritional benefits to humans: -intestinal bacteria produce vitamins, such as Vitamin K and Biotin -more microorganisms as move down GI Tract (most in colon) |
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What enables herbivores to digest cellulose |
Bacteria in cattle rumens produce cellulase which allows cows to digest celluse |
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Cecum |
microbial fermentation chamber of herbivores |
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3 hormones that aid in digestion |
Gastrin Secretin Cholecystokinin (CKK) |
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How does gastrin aid in digestion -negative feedback loop |
-Released from stomach -Stimulates stomach movements (increasing release of chyme) and secretion of (acidic) digestive juices ---> Stimulates secretion of HCl and Pepsin *Low pH inhibits Gastrin release |
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How does Secretin aid in digestion -negative feedback loop |
-Released from duodenum due to acidity of chyme (chyme release wasdue to gastrin - if acidic, Secretin is released) -causes pancreas to secrete bicarbonate (neutralizing chyme) *Slows down stomach movements, causing decrease in chyme release |
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How does Cholecystokinin (CCK) aid in digestion *negative feedback loop |
-Released by duodenum epithelial cells when fat in chyme (chyme release was due to gastrin; if fat in it, CCK is released) -Causes gallbladder to contract and release bile (also causes pancreas to release digestive enzymes *Slows stomach movements, causing decrease in chyme release |
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How does the liver convert and store nutrients? |
Gluconeogenesis: converts amino acids and other molecules into glucose Glycogenolysis: breaks down glycogen into glucose Also, controls fat metabolism by production of lipoproteins |
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Lipoproteins: -Description -Types |
= Core of hydrophobic fat and cholesterol with covering of hydrophilic proteins -Can be transported in blood (a way of transporting fat); ex: chylomicrons TYPES: High-Density Lipoproteins (HDLs) = "the good" -high ratio of protein to lipid -removes cholesterol from tissues and carries it to liver Low-Density Lipoproteins (LDLs) = "the bad" -Transport cholesterol in the body Very-Low Density Lipoproteins (VLDLs) = "the ugly" -Transport triglycerides to fat cells |
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What causes glycogenolysis and gluconeogenesis? Which occurs first? |
When blood glucose levels fall, insulin release decreases, and thus glucose uptake by cells also decrease -Glucagon release by pancreas causes glycogenolysis (short term fasting) and gluconeogenesis (long term fasting) |
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How do glucose levels effect nutrient storage - during absorptive period |
-Blood glucose levels increase --> pancreas stimulated to produce insulin -insulin release promotes uptake and utilization of glucose for metabolic activities and for synthesis of glycogen and fat |
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How do glucose levels affect nutrient storage - during post-absorptive period? |
-Blood glucose levels fall, insulin release decreases, and thus glucose uptake by cells also decrease -Glucagon release by pancreas causes glycogenolysis (short term fasting) and gluconeogenesis (long term fasting) -Most cells switch to fatty acids for fuel |
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What is the arcuate nuclues and what does it do?
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Part of hypothalamus - integrates feedback signals regulating food intake: -hormones that activate neurons in it inhibit feeding: -Leptin = released by fat cells in proportion to how much lipid they contain -Insulin -hormons that inhibit neurons activate feeding: -Ghrelin = released by stomach when empty |
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Ob and Db genes in mice |
Ob = code for protein leptin Db = code for leptin receptors -If have ob or db (recessive), will have loss of function of the Gene = weight gain |
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What % water are humans? Where is that water? |
60%: 2/3 is intracellular 1/3 is in extracellular fluids: ~20% in plasma ~80% in interstitial fluid |
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Why must we maintain water at certain levels in ECF? |
Solute concentration in ECF determines water balance in the cells -ECF ionic composition influences cell-function -important for nitrogenous waste elimination |
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Osmoregulation |
Management of Body's water content and solute compostion |
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Osomolarity |
Moles of Osmotically active solute per liter of solution = (Molarity) X (#particles in solute that dissolve) |
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2 solns of same osmolarity |
isoosmotic |
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2 solns at different osmolarity: -one at lower = ____ -one at higher = ____ |
Lower = hypoosmotic Higher = hyperosmotic |
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Osmolarity is a type of ______ |
Diffusion |
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Water flows from ___ osmotic solns to _____. |
From Low to High |
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Water transport is ALWAYS _____ |
Passive |
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What are the two factors that cause water movement (which way does water move with both)? |
(1) Osmolarity Differences (OSMOSIS) -from hypoosmotic -> hyperosmotic (up gradient) (2) Pressure Diferences (FILTRATION) -from high pressure -> low pressure (down gradient) |
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Two types of organisms in terms of balancing water balance - Types, features, Pros and cons |
Osmoconformers = isoosmotic with environment -don't actively adjust internal osmolarity -most stay in pretty constant environments Osmoregulators = control internal osmolarity independent of environment (either hypoosmotic or hyperosmotic regulation) -can live in environments that would be uninhabitable for osmoconformers (ex: all terrestrial, fresh water) -BUT must control internal osmolarity which is energetically costly |
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Most Vertebrates are regulate _____ and ______ |
Osmolarity AND ion concentration |
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Ion Regulators |
Selective in the ions conserved vs ions excreted |
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Why must nitrogenous waste by eliminated? What is nitrogenous waste? |
-Breakdown of proteins and nucleic acids lead to nitrogenous products - most commonly NH3. -Must eliminate to maintain health; also important for effect on osmoregulation -Most wastes are dissolved in water to eliminate (except CO2) -must be continuously excreted (NH3 very toxic), but water soluble so will also lose water, or converted |
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3 Ways Animals excrete Nitrogen |
(1) Excrete Ammonia = ammonotelic Animals (2) Convert ammonia to Urea to excrete = Ureotolic Animals (3) Covert Ammonia to Uric Acid to excrete = Aricotelic Animals |
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Features of Ammonia and ammonotelic animals |
-animals = aquatic animals and most bony fish -Toxic -ammonia is Water Soluble -excreted via diffusion across gills (usually passive) -low energetic cost of excretion |
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Features of Urea and Uretolic animals |
-animals = mammals, most amphibians, cartilaginous fishes -urea is water soluble (important for placenta - can pass through) -converted from NH3 to Urea (through CO2) -Relatively Non-Toxic -High Energetic cost of excretion |
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Features of Uretelic Acid and Uricotelic Animals |
-Animals = birds, insects, and reptiles -Convert NH3 to Uric Acid -Relatively Non-toxic -insoluble in water (important so doesn't expose embryo in egg) -excreted as semi-solid with little water loss -high energetic cost |
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humans mostly excrete nitrogenous waste as ____ but also secrete ____ (too much of which can lead to gout) and ______ |
Mostly = urea Also (too much of can lead to gout) = uric acid And = ammonia |
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Excretatory System |
The organs that control volume, concentration, and composition of the ECF and secrete wastes |
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Urine |
Output of excretatory systm; fluid containing nitrogenous wastes |
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3 Key processes in urine formation |
(1) Filtration = using pressure differences to separate the majority of wastes (2) Secretion = process of removing more waste (3) Reabsorption = reabsorbing waste into blood that is not to be remoed |
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What are the two main mechanisms of excretatory systems |
(1) Body Fluid is collected -through filtration through semipermeable membrane (excludes cells and large molecules) -pressure forces water and small solutes into excretatory systems -fluid collected = filtrate (once in excretatory tube) (2) Composition of body fluid is adjusted -active transport to reabsorb valuable solutes -non-essential solutes and wastes are secreted |
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How do circulatory systems play a role in excretatory systems |
Filtration is driven by pressure differences - if don't have a circulatory system (or it is open), must approach filtration differently (or not at all |
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Describe Protnephrida Excretatatory features (and features of an organism that has it) |
Ex: Flat worm = no circulatory system; -Network of tubules: *Tubule has a flame cell with a tuft of cilia (1) Cilia of Flame cell beat inside tubule, leading to negative pressure in tubule (2) Causing fluid to move in between tubule cells ---In end -> Filtrate is less concentrated than ECF, and exits through pores (thus conserve salts and excrete water) |
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Describe features of Metanephridia excretatory system (and features of an organism that has it) |
Ex: Annelids (Earthworms), with closed circulatory system Ciliated Nephrostome -> tubule -> nephridiope (open to outside) (1) High pressure inside circulatory system filters blood into coelom (Coleomic/Body Cavity) (2) Cilia on Nephrostomes guide coelomic fluid into Tubules (3) In tubules, have active Reabsorption and Secretion into the filtrate -> In end, have dilute urine (usually in a moist environment) |
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Describe features of Malphigian Tubules (and features of an organism that has it) |
Ex: Insects, open circulatory system **USES ACTIVE TRANSPORT, NOT FILTRATION Blind ended tubules open to gut (1) Tubules use active transport to transport uric acid, K+ and Na+ into tubules and water out (2) Waste travels to gut; in hindgut, Na+ and K+ are actively reabsorbed into hemolymph cavity (water follows osmotically) (3) Uric Acid forms colloidal suspension and eliminates waste (with little water) ***in end, have concentrated urine (with little water) |
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three examples of invertebrate excretatory systems |
Protonephridia Metanephridia Malphigian Tubules |
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key features of the nephron |
Glomerulus = ball of capillaries, site of blood filtration, makes direct contact with: Bowman's Capsule = first part of tubule Renal Tubule = filtrate passes through here, cells modify filtrate by reabsorption and secretion of solutes Afferent Arteriole = blood enters glomerulus from here Efferent Areteriole = blood leaves gloerulus from here Peritubular Capillaries = transport substances to and from renal tubes |
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bowman's capsule |
encloses glomerulus site of blood filtration |
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cells of Bowman's capsule |
Podocytes = in direct with glomerular capillaries |
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Pressure drives water and small solutes out of _______ and into _______ |
Out of glomerular capillaries and into Bowman's Capsule |
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Why is there a high filtration rate between Bowman's capsule and glomerular capillaries |
1) High capillary blood pressure 2) High permeability of glomerular capillaries and podyctes |
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Travel of filtrate (by large organ) |
Kidney ---> Ureters (collected here) ----> Urinary Bladder ----> Urethra (expels filtrate) |
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How does urethra expel filtrate |
Have 2 sphincters at base of urinary bladder Smooth muscle sphincter ---> involuntary control Skeletal Muscle Sphincter ---> voluntary control |
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Key analogy of Kidney |
Outer Cortex Inner Medulla -> broken into renal pyramids Renal Pyramids: collecting duct nephrons go through, collect filtrate into pelvis Pelvis: funnel shape extension of ureter; collects filtrate Renal Artery = bring blood supply Renal Vein = after filtration, blood leaves |
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Tubule Sections of Nephron starting at glomerulus |
1) Proximal Convoluted Tubule (PCT) 2) Loop of Henle: 3 segments: ----1-Thin Descending Limb ----2-Thin Ascending Limb ----3-Thick Ascending Limb 3) Distal Convoluted Tubule 4) Collecting duct (eventually leads to pelvis and ureter) |
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Peritubular capillaries |
Surround proximal and distal convoluted tubule |
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Vasa recta |
Network of peritubular capillaries parallel to the loops of Henle and Collecting Duct -drain off into venule, then vein to renal vein and back to systemic circut |
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Proximal Convoluted Tubule: -main function |
Site of most reabsorption of water and solutes -Active transport of Na+, glucose, and Amino Acids out of Tubules, and water follows osmotically -> taken up by peritubular capillaries and back to rest of body |
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PCT -features |
-Many microvilli --> increase surface area -Many mitochondria --> important for Active Transport |
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Importance of Loop of Henle |
Concentrates urine (due to countercurrent multiplier) -> due to tubular fluid flowing in opposite directions in ascending and descending limbs, which leads to creation of solute gradient in renal medulla (increasing osmolarity of ISF from outer cortex to inner medulla) |
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How does the Loop of Henle lead to increased concentration of inner medulla |
Cells of loop differ anatomically: Thin Descending Limb & Thick Ascending Limb: -No microvilli -Few mitochondria Thick Ascending Limb: -many mitochondria = for active transport |
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How different segments of the Loop of Henle vary |
Descending = losing water (many aquaporins) Ascending = Losing ions (few aquaporins)
Thick = Active transport (many mitochondria) |
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Thin descending Limb: Permeability What losing (and how) Osmolarity |
Permeable to water, impermeable to Na+ and Cl- -Loses water to ISF (via diffusion) -Before entering, osmolarity in tubule is same as in blood plasma |
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Thin ascending limb: permeability what losing (and how) osmolarity |
Permeable to Na+ and Cl-, impermeable to water -loses NaCl to ISF (via passive diffusion) -Beforing entering, osmolarity is very high in tubule |
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Thick ascending limb: permeability what losing (and how) osmolarity |
-Impermeable to Water -Loses NaCl to ISF (via active transport) |
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Purpose of blood flow through medulla (through vasa recta |
-Tubule needs nutrients, but vasa recta must conserve the concentration gradient. Does by: -blood flows down descending vasa recta (which is proximal to ascending loop of henle): loses water and gains solutes -blood flows down ascending vasa recta (which is proximal to descending loop of henle): gains water and loses solutes |
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aquaporins |
membrane proteins that form water channels - insert into cell membranes (on both sides of cell - facing lumen and facing bloodstream) |
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Where are there lots of aquaporins found in renal tubules; where are there few |
Lots = PCT, and descending loop of henle few = Ascending loop of henle |
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osmolarity of ISF and Tubules ______ as you go down |
Increases |
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Distal Convolutd Tubule: main function |
Fine tuning of ionic compostion and water reabsorption: -Active secretion and reabsorption of: Calcium, Phosphate, Bicarbonate, and Potassium -Hormone regulation: PTH and other hormones work here |
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Collecting duct: -where fluid comes from -composition of fluid -function |
Comes from Tubule (DCT) -has same concentration as blood plasma but different composition ---> now mostly urea -in collecting duct, concentrate uring: *is permeable to water --> increases osmolarity of filtrate -urea diffusion out adds to osmotic potential -in end, concentration same as ISF |
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Two ways that kidneys remove H+/add HCO3- from/to the blood |
(1) Through HCO3- conversion: 1-HCO3- is filtered out of blood at gomerulus and into the tubule lumen & Renal tubule cells secrete H+ into tubule fluid 2-H+ and HCO3- react to form CO2 in tubule lumen 3-CO2 diffuses back into tubule cells 4-CO2 is converted back into HCO3- in tubule cells and transported to ISF/blood (2) Through NH4+ formation 1-NH3 and HCO3- are produced in tubules by metabolism of glutamine 2-HCO3- is transported to ISF/Blood 2-NH3 is transported to lumen and combines with H+ to produce NH4+ |
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Results of kidney failure |
Salt and Water retention = high blood pressure Urea Retention = uremic poisoning Decreasing pH = acidosis |
|
Dialysis Treatment |
Pass blood through membrane channels bathed in a plasma like soln to remove waste: 1-take arterial blood from patient 2-dialyze blood across semipermeable membrane bathed with soln similar in concentration to blood plasma: --high glucose conc -> dialysis fluid has higher osmolarity than blood blasma, so water diffuses out of blood --concentration of ions that are the same in both = no net mvmt --bicarbonate ions = soak up H+, removing excess H+ from blood 3-used dialysis soln is discarded and blood returned to patient via a vein |
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Glomerular Filtration Rate |
Volume of blood plasma filtered per unit time |
|
Pair of humans filter ____ Liters per day. Most is _____ |
~180L Most is reabsorbed |
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Main 2 mechanisms for ensuring high glomerular blood pressure (to maintain high GFR) |
Dilation of afferent arterioles Constriction of efferent arterioles |
|
Name 4 hormones that can result in altered kidney function |
Angiotensin: increase BP Aldosterone (release stimulated by Angiotensin): increase BP ADH: increase BP ANP: decrease BP *increasing BP = increased GFR *decreasing BP = decreased GFR |
|
Describe how Renin release causes an increase in GFR |
(1) If GFR falls, kidneys release the enzyme renin (2) renin activates the hormone angiotensin (by converting angiotensinogen to angiotensin) (3) Angiotensin raises GFR (by increasing BP): 1-constricts efferent renal arterioles 2-constricts peripheral blood vessels 3-stimulates release of aldosterone from adrenal cortex - which increases Na+ reabsorption |
|
How is renin released |
DCT makes contact with glomerular afferent and efferent arterioles -Macula Densa = specialized cells in tubule ---> detect concentration of NaCl, if low, signal to: Juxtaglomerular Cells = specialized cells in arteriole ----> release renin **this can occur b/c if GFR is low, there is more time, so more NaCl is reabsobed, so NaCl is low -> so renin is released, leading to increased BP |
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how does ADH regulate blood pressure and blood osmolarity |
Insertts aquaporins on collecting duct to increase water permeability ---> leading to water retention which increases blood pressure decreases osmolarity |
|
how is ADH release controlled |
Osmoreceptor Neurons in hypothalamus: detect high blood osmolarity --> triggers release of ADH ---> increases blood pressure by increasing water retention Stretch Receptors in Aorta and Cartoid Arteries: detect high blood pressure --> inhibits release of ADH ---> decreases blood pressure |
|
ANP |
Atrial Natriuretic Peptide |
|
How does ANP regulate blood pressure |
-increased venous return stretches atria and muscle fibers release ANP -ANP leads to decreased reabsorption of Na+ in the kidney -increasing loss of Na+ and water ---> decreases blood volume and pressure |
|
After drinking lots of water, what hormone will increase |
ANP |
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Different species have different loops of henle. How do differing loops of henle reflect ability to concentrate urine |
Long loops = very concentrated urine -ex: desert rat - wants to conserve water Short loops = less concentrated urine -ex: birds, but use uric excretion as water conservation mechanism |