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77 Cards in this Set
- Front
- Back
cell signaling is______. The signaling cell_______. The target cell_________.
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communication between cells, sends the signal, receives the signal
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Types of cell signaling:
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Direct and Indirect
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Direct signaling
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-through Gap Junctions
-hydrophillic chemical messengers can travel directly through lipid membrane -typically involves movement of ions |
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Indirect signalling
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signaling cell releases a chemical messenger that binds to a receptor on the target cell and activates a signal transduction pathway.
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paracrine signaling
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-over short distance
-diffusion to nearby cell |
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autocrine signaling
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-over short distance
-diffusion back to the signaling cell |
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endocrine signaling
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-over long distances
-hormone is transported by the circulatory system |
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Neural signaling
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electrical signal travels along a neuron and releases a neurotransmitter
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Two main types of cell messengers
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1. hydrophilic
2. hydrophobic |
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Gap junctions
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-specialized protein complexes that create an aqueous pore between two adjacent cells
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Indirect signaling
3 Steps: |
1. release of chemical messengers from the signaling cell
2. transport of the messenger through the extracellular environment to the traget cell 3. communication of the signal to the target cell |
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release of chemical messengers
Hydrophobic and hydrophilic |
-hydrophobic messengers: can cross the cell membrane by diffusion
-Hydrophilic messengers: packed into vesicles where they are stored until released by exocytosis |
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exocytosis
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vesicles fuse with the plasma membrane and release contents
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Transport of hydrophilic messengers to the target cell
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the messengers dissolve in aqueous solutions like extracellular fluid and blood.
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transport of hydrophobic messengers to the target cells.
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-hydrophobic messengers bind to carrier proteins in the blood
-some do not bind to carrier proteins -circ system carries the free and bound messenger towards target cell -free messenger enters target cell and binds to receptor, bound messenger cannot enter the target cell -the decreasing concentration of free messenger causes bound messenger to dissociate from the carrier protein, allowing it to enter target cell. |
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carrier protein
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help hydrophobic messengers dissolve in aqueous solutions
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receptors for hydrophobic messengers
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are intracellular protiens
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receptors for hydrophilic messengers
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are transmembrane protiens
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Ligand, What it is and what it does
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chemical messenger that can bind to a specific receptor. The receptor changed shape when it binds to the receptor. Only corrected shaped ligand can bind to a receptor.
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ligand mimics, what they are and what they do
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Antagonist- block the receptor but produce no signal (decreases over all signal by decreasing available binding sites fro natural ligand)
Agonist- activates the receptor and produces a signal (signal can be produced when no natural ligand is present or signal is enhanced if natural ligand is present too) |
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More free ligand will ______response. More receptors will ______ response. Receptors can become_________.
Increasing affinity constant (Ka) will______ response |
increase, increase, saturated, increase
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Down Regulation
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constant exposure to the ligand will lead to a decrease in the number of receptors (receptor desensitization)
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Up-regulation
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constant exposure to ligand will lead to a increase in the number of receptors.
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Signal transduction pathways
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concert the change in shape of the ligand-receptor complex into a complex intracellular response.
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Transducers
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-convert signals from one form to another
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4 components of the signal transduction
ran to a rat |
1. Receiver: ligand binding receptor
2.Transducer: conformational change of receptor 3. Amplifier: signal transduction pathway increases the number of molecules affected 4. Responder: something that responds to the signal |
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Types of receptors
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-Ligand gated ion channels
-Receptor enzymes -G-protein coupled receptors -Intracellular receptors |
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Intracellular receptors
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can regulate the transcription of target genes by binding to the specific DNA sequences and increasing or decreasing mRNA production.
-The ligand-receptor complex translocates to the nucleus and DNA binding domain of the receptor binds to a specific DNA sequence and the transactivating domain interacts with TXN factors bound in the same region. |
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Ligand gated ion channels
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-ligand binds to the receptor
-receptor changes shape, opening the channel -ions move across the membrane -concentration and electrical gradients dictate the direction of ion movement -movement of ions changes ion concentration which alters membrane potential |
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Receptor Enzymes
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-when activated the catalytic domain starts a phosphorylation cascade
-names based on the reaction catalyzed ex tyrosine kinase, serine/threonine kinase, guanylate cyclase |
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G-protein coupled receptors
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-transmembrane protein interacts with intracellular g-protein.
-activate second messengers -have ability to bind guanosine nucleotides ( alpha subunits swap gdp for gtp when active, the active alpha subunit then dissociates and moves through membrane to interact with amplifier enzyme which then activates a second messenger) |
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second messenger Ca2+
1. synthesized by the enzyme: 2. action: 3. effect: |
1. none
2. binds to calmodulin 3. alters enzyme activity |
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second messenger cGMP
1. synthesized by the enzyme: 2. action: 3. effect: |
1. guanylate cyclase
2. activates protein kinases (usually PKG) 3.phosporylates proteins, open and closes ion channels |
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second messenger cAMP
1. synthesized by the enzyme: 2. action: 3. effect: |
1. adenylate cyclase
2. activates protein kinases usually PKA 3.phosphorylates proteins |
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second messenger Phosphatidylinositol
1. synthesized by the enzyme: 2. action: 3. effect: |
1.Phospholipase C
2.Activates protein kinase C, stimulates Ca2+ release from intracellular stores. 3. alters enzyme activity phosphorylates proteins |
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secretory cell of:
1. autocrine/paracrine 2.nervous 3. endocrine |
1. various
2. neuron 3. endocrine |
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target cell of:
1. autocrine/paracrine 2.nervous 3. endocrine |
1. most cells in body
2. neuron, muscle, endocrine 3. most cells in body |
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maximum signaling distance
1. autocrine/paracrine 2.nervous 3. endocrine |
1.short
2. long 3 long |
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signal type
1. autocrine/paracrine 2.nervous 3. endocrine |
1. chemical
2. chemical and electrical 3. chemical |
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Transport
1. autocrine/paracrine 2.nervous 3. endocrine |
1. extracellular fluid
2. synapses 3. circ system |
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speed
1. autocrine/paracrine 2.nervous 3. endocrine |
1. rapid
2. rapid 3. slower |
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duration of response
1. autocrine/paracrine 2.nervous 3. endocrine |
1. short
2. short 3. longer |
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Eicosanoids
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act only in paracrine and autocrine signalling
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prostaglandins
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involved in pain reception; blocked by many painkillers
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nervous system
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-collection of cells that can carry signals across long distances
-neurons allow electrical signals to be propagated across long distances within a cell |
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synapse
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region between two neurons or a neuron and other target cells
-gap junctions -neurotransmitters |
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endocrine system
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- sends chemicals (hormones) through the blood
-produced by endocrine glands -other chemicals can act as hormones ex neurohormones -nonendocrine organs like the heart can produce hormones |
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3 types of hormones
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-steroid
-peptide -amines |
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peptide hormones
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-are hydrophilic
-made in advance -stored in secretory vesicles -released by exocytosis -transported dissolved in plasma -have a short half life -receptors are located on cell surfaces -they activate second messenger pathways |
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Steriod hormones
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-are hydrophobic
-synthesized on demand -not stored -are released by diffusion -transported by carrier protiens -have a long half life -have receptors in cytoplasm or in nucleus (some on cell surface) -alter gene expression but some non genomic responsibilities as well |
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amines:
catecholamines |
-hydrophilic
-made in advance -stored in secretory vesicles -released by exocytosis -transport dissolved in plasma -short half life -receptors on cell surface -activates second messengers |
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amines:
thyroid hormones |
-hydrophobic
-made in advance -precurser is stored in secretory vesicles -released by diffusion -transported bound to carrier protiens -have long half life -receptors are located in the nucleus -alter gene expression |
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pepide hormones are sythesized in the
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rough ER
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steps in peptide hormone synthesis
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1. translated in rough er
2.preprohormone is in lumen, cleaved of signaling sequence and enters vesicle as prohormone 3.goes to golgi 4.in the secondary vesicle a peptide fragement is cleaved and active hormone present |
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synthesis of steriod hormones
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1. derived from cholesterol
2.enzymes for synthesis are in smooth ER and mitochondria 3. cannot be stored in cell so must be produced on demand -sloow effects except for the stress hormone cortisol which has rapid non genomic effects |
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three classes of steroid hormones
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1. mineralocorticolids-electrolyte balance ex. aldosterone
2. glucocorticoids-stress hormones ex. cortisol 3. reproductive hormones-regulate sex specific characteristics and reproduction |
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amine hormones
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-possess amine (-NH2)
-some true hormones -some neurotransmitters -some both (acetylcholine, serotonin, melatonin, histamines) - have diverse effects |
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exocrine cell signaling
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-secretions via ducts to the outside of the body including skin, respiratory surfaces and the gut
-cell to cell, pheromones, allelochemicals |
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Positive feedback
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output acts as further stimulus
-outside factor is required to shut off the positive feedback cycle |
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negative feedback
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output reduces the stimulus
can be direct, first, second or third order ect. |
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direct feedback
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-simplest system
-endocrine gland acts as the receptor, intergrating center and the endocrine gland. -stimulate endocrine gland which then sends hormone to target cell example: parathyroid hormone |
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first order feedback
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-stimulate sense organ
-signal is intergrated and then stimulates target cell |
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2nd order feedback
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-stimulate sense organ
-signal is intergrated and then stimulates endocrine gland -hormone is then sent to target cell |
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3rd order feedback
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-stimulate sense organ
-signal is intergrated and then stimulates endocrine gland -hormone is then sent to second endocrine gland that is then stimulated -2nd hormone stimulates target cell |
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parathyroid hormone
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stimulus: low plasma Ca2+
endocrine gland: parathyroid gland target organ: kidneys and bones Respones:kidneys retain calcium and bones release it. so plasma concentration of Ca+ increases and is negative feedback |
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epinephrine 2nd order feedback
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-flight or fright response
-sense organs preceives an alarming stimulus -sensory nerves send signal to the brain -brain intergrates the signal and sends signal out via motor nerves -adrenal medulla responds to signal by releasing epinephrine -epinephrine interacts with heart and muscles |
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Insulin
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-direct stimulus response and second order feedback
-cck-stimulates digestion -ach-major NT used during digestion -stretch receptors in digestive tract and glucose receptors and inc in blood glucose cause pancreas to secrete insulin |
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posterior pituitary
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-extension of hypothalamus
-neurons originate in hypothalamus and terminate in the posterior pituitary -cell bodies synthesize neurohormones that travel in vesicles down axons -eg oxytocin and vasopressin -first order endocrine pathway |
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anterior pituitary
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-hypothalamus synthesizes and secretes neurohormones
-portal system to anterior pituitary -tropic hormones cause release of another hormone -3rd order endocrine pathway |
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tropic hormones
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cause release of another home
ex. TSH stimulates the thyroid gland to release thyroid hormones |
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regulation of blood glucose is tightly controlled. To low__________To high___________. Hormones used____________. The hormones have ___________ pairing which means they__________________. Beta cells of pancreas release______ and alpha release__________.
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brain cannot function, osmotic balance of blood is disturbed, insulin and glycogen, anatgonistic pairing, have opposite effects, insulin, glycogen
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similarities between plants and animals pathways
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-use calcium as secondary messenger
-have pathways that involve protien kinases |
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differences between plants and animals pathways
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-plants do not have receptor tyrosine kinases or RAS protiens
-plants have unique transmembrane serine and threonine kinases |
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vertebrates vs invertebrates
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-all have nervous systems except sponges
-circ and endocrine systems developed independently in several groups -all vert use a series of steroid hormones and invert just use esterogen --insects/crustaceans use different series of steroids to regulate molting and metamorphosis |
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vertebrates horomones have alterations in the ______ tissues respond to a hormone rather then a change in the _____________
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-way, hormone
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prolactin
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-stimulates milk production in mammals and inhibits metamorphosis and promotes growth in amphibians and regulates water balance in fish.
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adrenal glands
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-on kidneys
-have interrenal and chromaffin tissue |