human physiology spring 2025: endocrine, cardiovascular, etc

endocrine glands of the body

pituitary, thyroid, parathyroid, adrenal, and pineal

Gs

stimulates adenylyl cyclase to produce cAMP, which then triggers protein kinase A

Gq

triggers phospholipase C to derive PIP2 from the plasma membrane in order to produce second messengers IP3 and DAG

receptor tyrosine kinases

hormone receptor binding causes tyrosine kinases on each receptor to cross phosphorylate; phosphorylated tyrosines of the receptors serve as docks for relay proteins which then get activated via phosphorylation on their own tyrosine amino acids

receptor guanylyl cyclases

water-soluble hormones bind to receptors, which then dimerize; dimerization triggers guanylyl cyclase components of the receptors to produce cGMP, which then activates protein kinase G

janus kinase coupled receptors

a water-soluble hormone binds to the JAK receptor which then dimerizes with a neighbor and they cross phosphorylate each other; the active JAKs then phosphorylate a tyrosine in the cytosolic portion of the receptor; STAT proteins dock and get phosphorylated (activated) before entering the nucleus to alter gene transcription to produce a cellular response

tropins

hormones that act on endocrine glands or tissues to regulate the secretion of another hormone

hormone secretion can be regulated by

the nervous system, chemical changes in the blood, mechanical organ signals, or other hormones

infundibulum

stem structure that connects the pituitary gland to the hypothalamus

somatotrophs

APG cells that secrete growth hormones

gonadotrophs

APG cells that secrete folic stimulating hormone (FSH) and luteinizing hormone

thyrotrophs

APG cells that secrete TSH

corticotrophs

APG cells that secrete adrenocorticotropic hormone (ACTH)

lactotrophs

APG cells that secrete prolactin

hypothalamic-hypophyseal portal system

blood flows the hypothalamus into portal veins that take it to the anterior pituitary gland, allowing the hypothalamic hormones to act on the pituitary gland immediately and directly

pro-opiomelanocortin (POMC)

the precursor to a variety of peptides that impact various aspects of homeostasis like appetite, cortisol levels, pain signals, and hormones including ACTH

follicle stimulating hormone

development of eggs and secretion of estrogen in females; production of sperm in males

posterior pituitary gland

made of neurosecretatory cells, so it stores and releases hormones synthesized by APG

oxytocin

neurosecretatory cells of the hypothalamus secrete this in response to uterine distention to initiate labor

calcitonin

regulates blood calcium levels by inhibiting osteoclasts, which break down bone into calcium and phosphate components

hypothyroidism

deficiency in thyroid hormones causes by thyroid dysfunction, lack of TRH from the hypothalamus or TSH from the anterior pituitary gland, or lack of iodine in the blood

parathyroid glands

made up of parafollicular cells called chief cells and oxyphil cells, the parathyroid gland chief cells release PTH to increase levels of calcium, magnesium, and phosphate ions in the blood via bone respiration (breakdown)

antagonistic hormones in the endocrine system

insulin and glucagon, PTH and calcitonin,

adrenal cortex

produces steroid hormones mineralocorticoids, glucocorticoids, and androgens in the outer glomerulosa, middle fasciculata, and inner reticularis respectively

aldosterone

regulates blood pressure and blood volume through the RAA pathway in response to dehydration, hemorrhaging, or sodium deficiency; also regulates levels of K+, Na+, and H+ in the blood to prevent acidosis

glucocorticoid function

protein breakdown, neoglycogenesis, lipolysis, stress response/resistance, anti inflammatory, and immune response depression

glucocorticoid negative feedback cycle

low glucocorticoids stimulates the hypothalamus to release CRH, which triggers the release of ATCH from the anterior pituitary, which then causes the adrenal cortex to release glucocorticoids as a homeostatic response

adrenal medulla

modified sympathetic ganglion of the autonomic nervous system made of chromaffin cells, which synthesize and release epinephrine and norepinephrine to augment the fight or flight response of the sympathetic nervous system

suprachiasmatic nucleus

the body’s internal biological clock located in the hypothalamus that establishes circadian (daily) rhythms (theoretically) in sync with the light/dark cycle based on visual input relayed to the retinohypothalamic tract

pineal gland

secretes melatonin, which is derived from tryptophan, to induce sleep, protect against free radicals, and regulate circadian rhythms

pancreas

the endocrine portion has cells called pancreatic leaflets that secrete hormones as part of the endocrine system: alpha cells secrete glucagon, beta cells secrete insulin, and delta cells secrete somatostatin

insulin uptake

insulin binds to an insulin receptor tyrosine kinase, cross phosphorylation occurs, insulin receptor substrates bind to the active (phosphorylated) sites and then trigger intracellular pathways for glucose transporters to bring glucose into the cell, thus lowering blood sugar levels

insulin functions

glycogenesis to turn glucose into glycogen in liver and skeletal muscle cells, inhibit catabolic processes that release glucose (glycogenolysis), and promote synthesis of triglycerides and proteins from preexisting fatty acids and amino acids

glucagon

targets hepatocytes to break down large glycogen molecules into smaller, usable glucose molecules through catabolic processes and the Gs adenylyl cyclase cAMP pathway

glucagon function

antagonistic functions to insulin, so glucagon forms glucose from non-carb sources and breaks down triglycerides and proteins into smaller components

stomach

produces ghrelin for stimulating appetite and gastrin for digestive juice secretion and digestive motility

skin and kidneys

contribute to the absorption of the active form of vitamin D3 as cholecalciferol and calcitriol are produced by the respective organs; vitamin D is crucial for calcium absorption into the blood stream

placenta

serves as the site of nutrient and waste exchange between the mother and the fetus during pregnancy and secretes several hormones involved in child development and mammary preparation

cause of craving for salty foods

an excess of aldosterone is released in response to low sodium levels in the blood

somatostatin

is released by delta cells of the pancreas and inhibits secretion of glucagon, insulin, and growth hormones. also slows nutrient absorption during digestion. can inhibit and be inhibited by the pancreatic polypeptide.

go to G protein IP3 receptor

oxytocin and ADH

FSH, LH, ATCH, TSH, CRH, PTH, calcitonin, glucagon

go adenylyl cyclase cAMP receptor

ANP

goes to guanylyl cyclase cGMP receptor

insulin

goes to tyrosine kinase receptor

prolactin, GH

go to janus kinase STAT receptor

glucocorticoids, estrogen, testosterone, progesterone, aldosterone, T3, T4, and cortisol

go to steroid receptors