Lecture 9 Flashcards
Control of hormone secretion s usually part of which type of feedback loop?
Negative feedback loop.
LSH and FSG are both released from the same signals.
Result depends on how the signal is received.
In the ovaries, which product feeds back to shut off FSH?
Estradiol.
PTH (parathyroid hormone).
Acts to increase blood calcium concentration. It stimulates osteoclasts in the bone to release more calcium from storage in bonds tissue, which increases blood calcium level.
Lactation.
Requires a lot of calcium; the decrease in calcium is detected by PTH, which acts on the bone and causes release of calcium into the blood. The calcium is then used to make the milk.
The pituitary gland is an important structure of the brain.
Infundibulum (stem-like stalk) connects the pituitary to the hypothalamus. Made up of 2 glands: anterior and posterior. It is also called the neurohypophysis.
Anterior pituitary.
Synthesizes trophic hormones . Process: released from the hypothalamus through portal vessels and reaches the anterior pituitary gland.
Growth hormone.
Causes uptake into bone.
ACTH.
Targets the adrenal cortex, causes release of aldosterone (a mineralocorticoid) and retention of sodium, as well as potassium secretion.
Gonadotropins (LH and FSH)/
They target the gonads; stimulate spermatogenesis and cause Leydig cells to secrete testosterone in males. In females, it stimulates the follicle: causes ovulation and formation of the corpus lute during pregnancy.
Does the anterior pituitary produce hormones?
No; it just secretes them. Examples: oxytocin and ADH.
Oxytocin.
Stimulates smooth muscle contractions.
Adenphyphysis.
2 parts: pars anterior (major portion) and the pars intermedia. This tissue is composed of irregular clumps of secretory cells supported by 5 connective tissue fibres and surrounded by a rich vascular network.
5 functional types of secretory cells in the adenophysos.
Somatotrophs (secrete GH- growth hormone, somatotropin), corticotrophs (secrete ACTH- adrenocorticotropic hormone and MSH- melanocyte stimulating hormone); Thyrotrophs (secrete TSH); lactotrophs (secrete PRL-prolactin); and gonadotropes (secrete LH and FSH).
How does GH stimulate growth?
It stimulates the liver to produce growth factors, which in turn accelerate amino acid transport into cells; it is an anabolic type of hormone. It also stimulates lipid metabolism: accelerates mobilization of lipids from cells and speeds up lipid catabolism; this helps break down lipids to use them as a source of energy; hyperglycaemic effect.
Insulin has opposite effects from GH.
Insulin from the pancreas promotes entry of glucose into the cells and promotes storage; GH stimulate triglyceride breakdown.
Ways that GH affects metabolism.
promotes protein anabolism, promotes lipid mobilization and catabolism, indirectly inhibits glucose metabolism by shifting energy to lipid metabolism, and indirectly increases blood glucose.
Adenohypophysis (anterior pituitary): prolactin (PRL).
Produced by lactotrophs in the anterior pituitary During pregnancy, PRL promotes development of the breasts, anticipating milk secretion. Oxytocin results in smooth muscle contractionL causes the milk to be ejected.
Adenohypophysis (anterior pituitary): tropic hormones.
Tropic hormones stimulate the endocrine glands: TSH, ACTH, FSH, LH.
Thyroid stimulating hormone (TSH).
Promotes and maintains growth and development of the thyroid, causes release of T3 and T4; regulates metabolism and calorigenic effect.
Adrenocorticotropic hormone (ACTH).
Promotes and maintains normal growth and development of the cortex of the adrenal gland. Stimulates the adrenal cortex to secrete some of its hormones (cortisol and aldosterone).
ACT promotes the secretion of which adrenal hormones?
Aldosterone and cortisol. Note: aldosterone can also be released in response to dehydration.
Follicle-stimulating hormone (FSH).
In females: stimulates follicle growth and estrogen secretion. In males: stimulates development of testes and spermatogenesis in the Sertoli cells.
Luteinizing hormone (LH).
In females: stimulates the formation and activity of corpus luteum of the ovary, triggering the release of progesterone and estrogen from the corpus luteum as well. LH also supports FSH in follicle maturation. In males: LH stimulates the Leydig cells in testes to develop and secrete testosterone.
