Endocrine System

The 2nd control system of the body, composed of endocrine glands and specialized endocrine cells

The (?) releases chemicals called hormones that regulate complex body processes. Hormones travel through the blood and alter the activity of target cells

Overall, the (?) regulates complex processes such as (?)

_______ are chemical substances secreted by endocrine cells into the extracellular fluids that regulate the metabolic activity of other cells in the body

Classification/s:

• Amino acid-based molecules (proteins, peptides and amines)

• Steroids

• Prostaglandins

A given hormone affects only certain tissue cells or organs, referred to as its (?)

Function/s:

• Change plasma membrane permeability or membrane potential by opening or closing ion channels

• Activate or inactive enzymes

• Stimulate or inhibit cell division

• Promote or inhibit secretion of a product

• Turn on or turn off transcription of certain genes

HORMONE FUNCTION & REGULATION

• Steroid and Thyroid hormones

• Hormones that are lipid-soluble molecules = diffuse through the plasma membrane

Process:

1. Once inside, the steroid hormone enters the nucleus and binds to a specific hormone receptor

2. Hormone-receptor complex then binds to specific sites in the cell’s DNA

3. Activates certain genes to transcribe messenger (mRNA)

4. mRNA is translated in the cytoplasm

5. Protein synthesis

• Protein or peptide hormones

• NOT water-soluble and are unable to enter target cells directly

• Instead, they bind to hormone receptors situated on the target cell’s plasma membrane and use a second-system messenger system

Process:

1. Hormone binds to the receptor protein on the plasma membrane

2. Activated receptor activates an enzyme

3. Enzyme catalyzes reactions to produce second-messenger molecules (cyclic AMP or cAMP or cyclic adenosine monophosphate)

4. cAMP stimulates a response/reaction inside the target cell

The stimuli that activate endocrine glands fall into three (3) major categories:

most common; endocrine glands are stimulated by other hormones

changes in blood levels of certain ions and nutrients stimulate hormone release

nerve fibers stimulate hormone release

Major endocrine glands are (?) glands that produce hormones that they release into the blood or lymph

• Pea-sized gland hanging by a stalk from the inferior surface of the hypothalamus

• It has two functional lobes—the anterior pituitary (glandular tissue) and the posterior pituitary (nervous tissue)

• not an endocrine gland in the strict sense because it does not make the peptide hormones it releases.

• Instead, it acts as a storage area for hormones made by hypothalamic neurons.

hormone released only during childbirth and nursing. It stimulates powerful contractions of uterine muscle during sexual relations, labor and breast feeding. It also causes milk ejection (“letdown reflex”) in a nursing woman.

• DIURESES – urine production

• Water is a diuretic fluid and a powerful inhibitor of ADH release

• It causes the kidneys to reabsorb more water from the forming urine = urine volume decreases and blood volume increases

• ADH also increases blood pressure by causing constriction of arterioles (small arteries) (Vasopressin)

Posterior Pituitary 2 Hormones

• Condition of excessive urine output due to hyposecretion of ADH

• S/Sx: continually thirsty and drink huge amounts of water

• “Master Endocrine Gland”

• All (?) hormones (1) are proteins (or peptides), (2) act through second-messenger systems, and (3) are regulated by hormonal stimuli

• General metabolic hormone

• Direct effect on growth of skeletal muscles and long bones of the body, and thus it plays an important role in determining final body size

• Stimulates most target cells to grow in size and divide

• Causes breakdown of fats for energy

• Saves glucose to maintain blood sugar homeostasis

Hyposecretion of GH during childhood; Body proportions are fairly normal, but the person as a whole is a living miniature (with a maximum adult height of 4 feet)

Hypersecretion of GH during childhood; Individual becomes extremely tall; height of 8 to 9 feet is common. Again, body proportions are fairly normal.

• Hypersecretion of GH after long bone growth has ended during adulthood

• Cause: result from tumor on pituitary gland

• Enlargement of facial bones particularly the lower jaw and bony ridges of underlying the eyebrows, feet and hands

• Enlargement of heart and other organs

• Protein hormone structurally similar to growth hormone

• Target organ/cell: Breast (mammary glands)

• Stimulates and maintains milk production by the mother’s breasts after childbirth

Anterior Pituitary 5 Hormones

They regulate the hormonal activity of the gonads (ovaries and testes)

2 Gonadotropic Hormones

• Female: stimulate follicle development in ovaries in women. As follicles mature, they produce estrogen and eggs are readied for ovulation.

• Male: stimulates sperm development

• Female: egg ovulation in women to produce progesterone and estrogen

• Male: stimulates testosterone production in the testes

Hyposecretion of FSH, the lack of ability to successfully reproduce in both males and females

Hyposecretion of LH, inability to complete one full term of pregnancy

• Also called as “thyroid-stimulating hormone” (TSH)

• Influences the growth and activity of the thyroid gland

Hormone that regulates the endocrine activity of the cortex portion of the adrenal gland

• Small, cone-shaped gland that hangs from the roof of the third ventricle of the brain (EPITHALAMUS)

• Melatonin – primarily responsible for regulating your body’s circadian rhythm to manage natural sleep cycle; peak level occurs at night and makes us drowsy and lowest levels occurs during daylight.

primarily responsible for regulating your body’s circadian rhythm to manage natural sleep cycle; peak level occurs at night and makes us drowsy and lowest levels occurs during daylight.

• Located at the base of the throat; just inferior to the Adam’s apple

• Fairly large gland consisting of two lobes joined by a central mass or isthmus

• Internally, it is composed of hollow structures called follicles which store a sticky colloidal material that form the thyroid hormone

• The thyroid gland makes two (2) hormones:

• Thyroid hormones

• Calcitonin

The thyroid gland makes two (2) hormones

“Body’s Major Metabolic Hormone”

It has two (2) iodine-containing hormones:

• Thyroxine (T4)

• Triiodothyronine (T3)

Thyroxine has (?) iodine atoms, whereas triiodothyronine has (?)

It controls the rate at which glucose is “burned” or oxidized, and converted to body heat and chemical energy (ATP)

It is also important for normal tissue growth and development, especially in the reproductive and nervous systems

It is an enlargement of the thyroid gland due to iodine deficiency in diet

Thyroid-Stimulating Hormone ”calls” for the release of thyroxine (T4), but as the peptide part of the molecule is made, the thyroid gland enlarges because the protein component is nonfunctional without iodine, thus, a continuous production of the peptide component

A type of dwarfism and hypothyroidism in which adult body proportions remain child-like, with a proportionally longer torso and shorter legs compared to normal adults

• Lack of thyroxine from birth or before birth; could be lack of thyroid gland or lack of iodine in mother

• severe irreparable mental defects

• Stunted growth

• Reduced growth and function of many organs

Tx: Hormone replacement therapy in early diagnosis to prevent mental impairment and deficiencies

Hypothyroidism or hyposecretion of thyroxine (T4) occurring in adults

• Characterized by both physical and mental sluggishness (but no mental impairment)

• Cause/s: viral infection, cancer, radiation exposure, autoimmune disease

• S/sx: puffiness of the face, fatigue, poor muscle tone, low body temperature (the person is always cold), obesity, and dry skin

• Medx: Oral thyroxine (T4)

Hyperthyroidism generally from a tumor on the thyroid gland

• Thyroid gland enlarges

• (+) Exophthalmos – bulging of the eyes

• S/sx: high metabolism, heat intolerant, rapid heartbeat, weight loss, nervous and agitated behavior• Tx: surgical removal of tumor or part of the affected thyroid gland or use of thyroidblocking drugs or radioactive-iodine to destroy some of the thyroid cells

bulging of the eyes

• Decreases the blood calcium ion level by causing calcium to be deposited in the bones

• Released directly to the blood in response to an increasing level of blood calcium ions

Tiny masses of glandular tissue most often found on the posterior surface of the thyroid gland

• Typically, there are (?) parathyroid glands on each thyroid lobe

• It secretes parathyroid hormone (PTH)

• Most important regulator of calcium ion (Ca++) homeostasis of the blood

• Parathyroids release PTH to stimulate the osteoclasts when calcium in the bloodstream drops below a certain level

• PTH also stimulates the kidneys and intestines to absorb more calcium ions (from urinary filtrate and food)

uncontrollable spasms or rapid muscle twitching when calcium ions fall too low

massive bone destruction; large punched-out holes in the bone matrix (X-ray). Fragile and brittle bones.

• Located in the upper thorax, posterior to the sternum

Large in infants and children, decreases in size throughout adulthood and by old age, it is composed mostly of fibrous connective tissue and fat

Produces a hormone called thymosin

essential for normal development of a special group of white blood cells (T lymphocytes) and the immune response

Also called “suprarenal glands” are two glands curved over the top of the kidneys like triangular hats

Adrenal Glands two (2) parts:

Adrenal Glands:

outer; made of glandular tissue

Adrenal Glands:

inner; made of neural tissue

Hormones of Adrenal Cortex

Hormones of Adrenal Cortex:

three major groups of steroid hormones produced by the adrenal cortex

Hormones of Adrenal Cortex:

Corticosteroids 3 major groups

• Regulates mineral (or salt) content of the blood, particularly sodium (Na+) and potassium (K+) ions

• Water and electrolyte balance

• When (?) increases, the kidney reabsorb increasing amounts of sodium (Na+) ions and secrete more potassium (K+) into the urine. When sodium is reabsorbed, water follows.

• Renin – enzyme produced by the kidneys to release (?) when blood pressure drops

enzyme produced by the kidneys to release aldosterone when blood pressure drops

• Promote normal cell metabolism and help the body resist long-term stressors, primarily by increasing the blood glucose level

• High (?) = fats and proteins are broken down and converted to glucose

• Controls inflammation and reduces pain

• Also called “Adrenal Androgens”

• Androgens – male sex hormones (mostly)

• Estrogens – female sex hormones

• Stimulate pubic and axillary hair growth (both male and female) and sex drive in females

• Hypersecretion = masculinization regardless of sex

• Hirsutism – increase in body hair in a masculine pattern such as a beard in females

increase in body hair in a masculine pattern such as a beard in females

masculinization regardless of sex

Low levels or hyposecretion of all adrenal cortex hormones, especially aldosterone and cortisol

Hypersecretion of cortisol and androgens due to a tumor on the adrenal cortex

Hormones of the Adrenal Medulla

(?) stimulates the adrenal medulla via sympathetic nervous system (fight or flight response)

• Located close to the stomach in the abdominal cavity

• Both an exocrine gland and an endocrine gland

• PANCREATIC ISLETS (Islets of Langerhans) – little masses of endocrine (hormone-producing) tissue

PANCREAS:

Two (2) important hormones produced

• Released from the pancreatic islets

• Helps the cells absorb glucose, reducing blood sugar and providing the cells with glucose for energy

• Without (?), cells are unable to use glucose as fuel and they will start malfunctioning

• Insulin moves sugar from the blood into your cells to be stored or used for energy

• With diabetes, your body either doesn’t make enough insulin or can’t effectively use the insulin it makes

• (N) blood glucose: 80 to 120 mg/100ml

• Released from the pancreatic islets

• Acts an antagonist of insulin

• When blood sugar levels are too low, the pancreas releases (?)

• (?) instructs the liver to release stored glucose, which causes blood sugar to rise

• Ovaries (female) and Testes (Male)

• Both has endocrine and exocrine function

• The major differences from the adrenal gland and gonads when producing sex hormones are the source and relative amounts of hormone produced

Hormones of the Ovaries

paired, slightly larger than almond-sized organs located in the pelvic cavity

development of sex characteristics in women (growth and maturation of the reproductive organs)

menstrual cycle

Hormone of the Testes

paired oval-shaped organs of the male and are suspended in a sac called the scrotum, outside the pelvic cavity

growth and maturation of the reproductive system organs to prepare the young man for reproduction. It also causes the male’s secondary sex characteristics (growth of facial hair, development of heavy bones and muscles, and lowering of the voice) to appear and stimulate the male sex drive.

ENDOCRINE GLANDS

Other Hormone Producing Tissues and Organs

• A temporary organ formed in the uterus of a pregnant woman

• Produces several protein and steroid hormones that help maintain the pregnancy and pave the way for delivery of the baby

• In the 3rd month of pregnancy, the (?) is the one producing estrogen and progesterone, while the ovaries become inactive for the rest of the pregnancy

Hormones of the Placenta

early pregnancy; stimulates to continue production of estrogen and progesterone so that the lining of the uterus is not sloughed off during menstruation

hormone that works with estrogen and progesterone in preparing the breasts for lactation.

hormone produced in a pregnant woman during labor; it causes the mother’s pelvic ligaments and the pubic symphysis to relax and become more flexible, which eases birth passage.

During old Age:

• Gradual decrease efficiency of endocrine system and hormones

• Mildly hypothyroid

• Decrease insulin production = type 2 diabetes