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.
Name 2 gonadotropins.
FSH and LH.
Through which feedback pathway does the hypothalamus adjust secretions of the anterior pituitary?
Negative feedback.
FSH levels at menopause.
Levels rise.
FSH on the ovary in normal circumstances.
FSH stimulates follicle growth. Follicle continues to grow, reaching a critical size as the level of estrogen increases. Estrogen then reaches a critical level, sending positive feedback through LH. LH release causes ovulation, which leads to formation of the corpus luteum; progesterone levels increase. If conception does not occur, the corpus luteum is destroyed, leading to a drop in progesterone.
FSH levels on the ovary at menopause
Menopause: running out of oocytes (eggs). FSH tries to grow a follicle, but never gets the feedbackk inhibition from LH; FSH levels will rise a lot. There is no spike in estrogen, since there is no formation of the follicles. Body temperature fluctuates a lot. Homeostasis eventually forces this to shut down.
How do hypothalamic regulatory hormones reach the anterior pituitary?
hypothalamic-hypophyseal portal system: direct connection to the hypothalamus.
Corticotropin releasing hormone (CRH) and which hormone are released in conjunction from the anterior pituitary?
ACTH.
Hypophyseal portal system.
An arrangement of blood vessels in which blood from one exiting tissue is immediately carried to a second tissue before returning to the heart.
Hormones released from the hypothalamus to the anterior pituitary in the hypophyseal portal system.
Growth hormone releasing hormone (GHRH), growth hormone inhibiting hormone (GHIH), corticotropin releasing hormone (CRH), thyrotropin releasing hormone (TRH), gonadotropin releasing hormone (GnRH), prolactin releasing hormone (PRH), and prolactin inhibiting hormone (PIH).
Hypothalamus and the posterior pituitary,
Neurosecretory cells have their bodies in the hypothalamus and their axon terminals in the posterior pituitary, They do not produce the hormones, merely secrete them,
Does the posterior pituitary make hormones?
No, it simply secretes them.
3 methods of hormone pathology.
Hormone excess, hormone deficiency, and abnormal responsiveness of target tissues.
Hormone excess: Cushing’s disease.
Excessive amounts of cortisol. Normal cortisol action: protein breakdown, glucose formation, lipolysis, anti-inflammatory effect, and depression of immune response. Hypersecretion of cortisol: a tumour of the adrenal gland secretes an excess of ACTH, which stimulates excessive secretion of cortisol. There is a breakdown of muscle proteins and redistribution of fat, resulting in “moon face:, pendulous abdomen, and flushed appearance.
Hormone deficiency: underachieve thyroid.
Normal actions of thyroid hormones: increase BMR, stimulate use of oxygen to make ATP, calorigenic effect, stimulates protein synthesis and increased use of glucose and fatty acids for ATP production, enhances the actions of catecholamines (epinephrine and norepinephrine), and accelerates body growth,. Deficiency: swelling of facial tissue (puffiness), slow heart rate, low body temperature, sensitivity to cold, dry hair and skin. It can lead to iodine deficiency, stress, and congenital.
Abnormal responsiveness of target tissueL Type 2 diabetes,
Normal action of insulin: accelerates facilitated diffusion of glucose into cells, speeds up conversion of glucose into glycogen, increases uptake of amino acids, increases protein synthesis, lipogenesis, slows glycogenolysis, and slows gluconeogenesis. Abnormal response causes high blood glucose weight loss, excessive e thirst, and frequent urination.
Type I diabetes.
Production of insulin is inhibited.
Type II diabetes.
Insulin is present in large amounts, but cells are not responding to it.
Which components balance calcium ion use?
Calcitonin, parathyroid hormone, and vitamin D.
