What is a hormone?
a molecule released in one part of the body but regulates the activity of cells in other parts of the body. (excites or gets moving)
What are exocrine glands?
(outside) secrete their products into ducts that carry the secretions into body cavities, into the lumen of an organ or to the outer surface of the body
Exocrine glands are sweat, oil, mucous, and digestive glands
What are endocrine glands?
(within) secrete their products(hormones) into the interstitial fluid surrounding their secretory cells rather than into ducts
What is contained in the sndocrine systme?
- Hypothalamus Pancreas
- Testes Ovaries
- Thymus Kidneys
- Stomach Small intestines
- Heart Placenta Liver Skin
- Adipose tissue
What is a down-regulation and up-regulation?
Down-regulation is a present hormone in excess # of receptors on target cells may decrease (less sensitive to a hormone)
Up-regulation is when a hormone is deficient, the number of LH receptors increases to make the target tissue more sensitive to the hormone
Chemicial class: Lipid/fats soluable hormones
Steroid hormones-derived from cholesterol
Thyroid hormones-are synthesized by attaching iodine to the amino acid tyrosine
Nitric Oxide-is a gas that serves as both a hormone and a nuerotransmitter
Chemical class: Water soluable hormones
Amine hormones- synthesized by modifying certain amino acids
Peptide hormones- consist of chains of 3 to 49 amino acids
Protein hormones- include 50 to 200 amino acids include human growth hormone and insulin
Eicosanoid hormones-derived from arachidonicacid, 20-carbon fatty acid
What are transport proteins and their functions?
Bind to lipid soluable hormones; synthesized by cells in the liver.
- Functions: 1. make lipid-soluable hormones temporarily water-soluable thus increasing their soluability in blood.
- 2. Retard passage of small hormone molecules through the filtering mechanism in the kidneys, thus slowing the rate of hormone loss in the urine.
3. They provide a ready reserve of hormone, already present in the blood stream.
What is free-fraction?
it diffuses out of capillaries, binds t receptors and triggers hormonal responses. As free hormone molecule leave the blood and bind to their receptors, transport proteins, release new ones to replenish the free fraction.
Explain the Action of Lipid-soluable hormones
(bind to their receptors within target cells)
- 1. (detaches, blood, interstitial fluid, lipid bilayer then to cell)
- Lipid-soluable hormone molecule detaches from its transport protein in the bloodstream, then diffuses from the blood through interstitial fluid and through the lipid bilayer of the plasma membrane into a cell.
- 2.If the cell is a target cell, the hormone binds to and activates receptors located within the cytosol or nucleus. The activated receptor-hormone complex then alters gene expression by turning specific genes on or off.
- 3. As the DNA is transcribed, new messenger RNA(mrna) forms, leaves the nucleus, enters cytosol. There it directs synthesis of a new protein, often an enzyme on the ribosomes.
4. New proteins alter the cell's activity and cause the responses typical of that hormone.
Explain the action of water-soluable hormones
- 1. Water soluable hormone(first messenger) diffuses from the blood through interstitial fluid and then binds to its receptor on the exterior surface of a target cell's plasma membrane.
- 2. as a result of the binding, the enzyme: adenylate cyclase, converts ATP to cAMP because the enzyme's active site is on the inner surface of the plasma membrane, this reaction occurs in the plasma membrane, this reaction occurs in the cytosol of the cell.
- 3. cyclic AMP(2nd messenger) activates several enzymes
- 4. Activated enzymes catalyze reactions that produce physiological responses
- 5. After a brief period, cAMP is inactivated by an enzyme called phosphodiesterase. Thus the cell's response is turned off unless new hormone molecules continue to bind to their receptors on the plasma membrane.
What is the first and second messenger?
First-A water-soluable hormone binds to its receptor at the surface of the plasma membrane
- Second-stimulated by the first messenger inside the cell, where specific hormone stimulated responses take place
- ex: cyclic AMP(cAMP)
What are the effects of hormone interactions?
Responsiveness depends on1. Hormone concentration in the blood 2. abundance of the targets cell hormone receptors3. Influences exerted by other hormones. A target's cell responds more vigorously when the level of a hormone rises or when the target cell has more receptors
What are synergistic and antagonist effects?
Synergistic effect-the effect of 2 hormones acting together is greater than the effect of each hormone acting alone
Antagonist effect-one hormone opposes the actions of another hormone ex: insulin
Explain the control of hormone secretion?
- Regulated in 3 ways
- 1. Signals from the nervous system
- impulses to the adrenal medulla alter the release of epinephrine
- 2. Chemical changes in the blood
- Blood ca2+ level regulates the secretion of parathyroid hormone
3. Other hormones-Adrenocorticotropic hormone stimulates the release of cortisol by the adrenal cortex
What are the 7 hormones of the anterior pituitary and what are they secreted by?
- 1.Human growth hormone(hgh) secreted by somatotrophs
- 2. Thyroid stimulating hormone(tsh) secreted by thyrotrophs
- 3. Follicle-stimulating hormone (fsh) secreted by gonadotrophs
- 4. Lutinizing hormone(LH) secreted by gonadotrophs
- 5. Prolactin(PRL) secreted by lactotrophs
- 6. Adrenocorticotropic hormone(ACTH) secreted by Corticotrophs
- 7. Melanocyte(MSH) secreted by cortocptrophs
What are the 7 hormones of the anterior pituitary's hypothalamic releasing hormone and hypothalamic releasing hormone(stimulated secretion) and hypothalamic inhibiting hormone(suppress)?
- 1. HGH releasing hormone:
- inhibiting hormone:
- 2. TSH thyrotropin releasing hormone and inhibiting hormone
- 3. FSH gonadtropin releasing hormone and no inhibiting hormone
- 4. LH gonadtropin releasing hormone and no inhibiting hormone
- 5. PRL prolactin releasing hormone(prh) and prolactin inhibiting hormone
- 6. Adrebocorticotropic hormone(ACTH) CRH releasing hormone and no inhibiting hormone
- 7. MSH CRH releasing hormone and dopamine inhibiting hormone
What is the pituitary gland and hypothalamus?
Both regulates growth, development, metabolism, and homeostasis.
Pituitary-(hypophysis) the "master" endocrine gland, it secretes several hormones that control other endocrine glands synthesize 7 different hormones
Hypothal-below the thalamus, links nervous and endocrine system. Cells in hypothalamus synthesize at least 9 different hormones
What does the pituitary gland contain?
- -lies in sella turcica of sphenoid bone
- -attaches to hypothalamus by a stalk(infundibulum) means funnel
*Anterior pituitary-influenced by hormones from hypothalamus
- *hypophyseal portal system-blood flows from capillaries in hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary
- *Superior hypophyseal arteries-branches of the internal carotoid arteries, bring blood into the hypothalamus, where the arteries divide into a capillary network(primary plexus)
- *hypophyseal portal veins-blood drains into it and passes down the outside of the infundibulum
- *Secondary plexus-formed by hypophyseal veins(capillary network)
Explain the control of secretion by anterior pituitary?
Releasing hormones-stimulate secretion of anterior pituitary hormones. Secreted by neurosecretory cells in hypothalamus.
Inhibiting hormones-Suppress secretion of anterior pituitary hormones
What are neurosecretory cells?
clusters of specialized neurons contained in hypothalamus synthesize hypothalamic releasing and inhibiting hormones in their cell bodies and package hormones inside vesicles, which are transmitted within axons of the neurosecretory cells to their axon terminals.
Explain anterior hypophyseal veins
Hormones are secreted by anterior pituitary cells pass into the secondary plexus capillaries which drain into anterior hypophyseal veins and out into the general circulation.
Tropic hormones/tropins-anterior pituitary hormones that influence another endocrine gland
Gonadtropins-regulate functions of the gonad
Describe the adrencorticotropic hormone (1/7) ACTH
stimulates the production and secretion of glococorticoids, primarily cortisol by the cortex of adrenal glands
- -Corticotropin-releasing hormone-released from hypothalamus stimulates the anterior pituitary to secrete ACTH.
- As the blood rises, secretion of both ACTH and corticotropin-releasing hormone drops due to negative feedback suppression of the anterior pituitary and hypothalamus
Describe the human growth hormone(HGH)(2/7) and the IGF functions
Human Growth hormone HGH-
the most plentiful anterior pituitary hormone. The main function of HGH is to promote synthesis and secretion of small protein hormones called IGF(insulin like growth factors) similar to insulin, responds to human growth hormone, cells in liver, skeletal muscles, cartilage, bones and other tissues secrete IGF's.
?What are the 2 hypothalamic hormones that control secretion of HGH and the 10 items blood glucose level regulates GHRH and GHIH secretes
- 1. GHRH-Growth hormone-releasing hormone, promotes secretion of human growth hormone
- 2. GHIH-Growth hormone inhibiting hormone suppresses GHRH
- Blood glucose level is a major regulator of GHRH and GHIH secretion
- 1. Hypoglycemia-abnormally low blood glucose level, stimulates the hypothalamus to secrete GHRH, which flows through the hypophyseal portal veins to the anterior pituitary
- 2. GHRH stimulates the anterior pituitary to release human growth hormone
- 3. HGH stimulates secretion of IGF's which speed up breakdown of liver glycogen into glucose, causing glucose to enter the blood more rapidly
- 4. As a result, blood glucose rises to the normal level
- 5. An increase in blood glucose above the normal level inhibits release of GHRH
6. Hyperglycemia-abnormally high blood glucose concentration, stimulates the hypothalamus to secrete GHIH
- 7. On reaching the anterior pituitary in portal blood, GHIH inhibits secretion of HGH
- 8. A low level of HGH and IGF's slows breakdown of glycogen in the liver, and glucose is released into the blood more slowly.
- 9. Blood glucose falls to normal level
- 10.A decrease in blood glucose below normal level(hypo) inhibits release of GHIH