Hmmm those are definitely good to know. I'd say ADH and aldosterone are two biggies, and I'd know the FLAT PEG mnemonic for the anterior pituitary. FLAT (FSH, LH, ACTH, TSH) are "tropic hormones", so they act on an organ which then releases something to effect change in the ultimate, target organ and PEG (Prolactin, Endorphins, and Growth Hormone) are "direct hormones", which bind directly to the target, affected organ. To make that make more sense, I guess I'll talk about a whole pathway? So Corticotropin Releasing Factor (CRF) is released from the hypothalamus into the hypophyseal portal system (bloodstream), swims on over to the anterior pituitary, binds, stimulates release of ACTH, ACTH swims waaaaaay over to the adrenal cortex, which releases cortisol, a glucocorticoid. The adrenal cortex ITSELF wasn't "changed" by the ACTH, to the ACTH is a tropic hormone. Then the cortisol does what it does (increased gluconeogenesis, decreased (?) protein synthesis, decreased inflammation/immunological response, and a bunch of other crap I really don't understand). The majority of the pituitary hormones work like that: 1) hypothalamus secretes its hormone (usually called a "releasing factor"-->2) pituitary secretes its hormone-->3) other crap happens!
Huh, I actually don't think I know which ones are steroid vs. peptide... I think estrogen, testosterone, glucocorticoids and mineralocorticoids are steroid and the rest except T3 and T4 are peptide?
But yeah, ADH and aldosterone: respond to the same thing, low blood volume (or high blood osmolarity, same thing), and act to increase blood volume by decreasing excretion of water and increasing reabsorption of it, but by very different pathways. ADH, secreted by the posterior pituitary (which is essentially just an extension of the hypothalamus that secretes oxytocin or ADH in response to action potentials from the hypothalamus), binds to the collecting ducts of the kidney tubule and makes the pores in the duct physically bigger, so that water flows out of the tubule and into the bloodstream (I don't know the exact mechanism by which this is done but I feel like that's totally unnecessary to know).
Aldosterone is a mineralocorticoid (so, a steroid hormone) released by the adrenal cortex in response to the renin-angiotensin pathway or ACTH bound to ACTH receptors on the adrenal cortex. Essentially, when blood volume is low (or, more specifically, blood pressure is low), renin is secreted by the juxtaglomerular apparatus (I think it's a part of the nephron right next to the glomerulus? hahaha), which converts inactive angiotensinogen into angiotensin I. Angiotensin I isn't really potent, so it pretty much just sits around, but ACE (Angiotensin Converting Enzyme) converts this active form of angiotensin into angiotensin II, which in and of itself is very potent and has a powerful vasoconstricting effect, leading to increased blood pressure. Angiotensin II binds to (receptors, I guess) on the adrenal cortex and releases aldosterone, which binds to Na+/K+ pumps in the collecting duct of the kidney tubule, changing their activity so that more Na+ leaves the tubule and is reabsorbed into the bloodstream, and so that K+ is pushed into the tubule (along with H+ protons), and excreted. Water follows the Na+ out of the tubule and into the bloodstream, so blood vessels experience increased blood pressure due to aldosterone's effects (in tandem with angiotensin II). Oh, just a cool note on ACE: ACE inhibitors are common ways to treat hypertension because angiotensin I pretty much does squat to increase blood pressure, so by not being able to be converted to angiotensin II--> aldosterone, the renin-angiotensin pathway is cut short and the patient experiences decreased blood pressure! ARB's are also common, they're antagonists to angiotensin II receptors.
Whew, sorry for the ridiculously long post, that was good to review for me. Totally suck at glucocorticoids so I should go look those up. Hope that helped a bit, tots!
Could someone go through the menstrual cycle, por favor? I'm having some trouble understanding it fully.
Merci!
