endocrine 2 Flashcards
pituitary gland is the ___ gland of the body
it is under control of the ___
master gland
hypothalamus
pituitary & hypothalamus are physically connected
pituitary gland is a ___ structure that hangs off the bottom of the ___
what are its lobes?…
lobe-like
hypothalamus
anterior & posterior lobe…both are connected to hypothalamus by hypothalmic hypophysial tract
bottom of the hypothalamus is a little swelling called ___, then goes down and connected to ___
median eminence
pituitary
the posterior pituitary looks like it has ____
neurons (has cell body, axons, terminals) - they started out as neurons but have evolved into endocrine cells (called neurosecretory cells) –> posterior pituitary called the neurohypophysis (pars nervosa)
neurosecretory cells do not generate APs or secrete neurotransmitters, instead, they synthesize and secrete hormones directly into bloodstream (hormones synthesized in cell body of neurosecretory cells then trafficked down axons & released into secretory system from terminals)
there are 2 groups of neurosecretory cells found in posterior pituitary:
where are they located?
supraoptic nucleus (above optic chiasm)
paraventricular nucleus (next to a ventricle of brain)
(named by their location)
supraoptic nucleus synthesizes & secretes ___
paraventricular nucleus synthesizes & secretes ___
ADH (vasopressin)
oxytocin
ADH and oxytocin are both ____
what is major diff b/w them?
peptide hormones (composed of 9 peptides)
major diff is ADH has an arginine instead of leucine at 2nd to last peptide –> so ADH often called arginine vasopressin
regulation of ADH secretion? what is its signal and mechanism?
- osmotic receptors in major arteries sense conc of NaCl in blood - indirect measure of dehydration
- BP drops (sensed in aortic arch and carotid sinus)
- atria of heart stress less as they fill (atrial stretch receptors respond to changes in blood volume)
signals sent to hypothalamus & active supraoptic nucleus to synthesize & secrete ADH –> ADH circulates and targets collecting duct & binds to receptor –> activates G proteins, bind GTP –> activate adenylate cyclase –> ATP to cyclic-AMP –> activates PKA by pulling off regulatory subunit –> PKA phosphorylates aquaporin –> increases insertion of aquaporin channels in collecting duct membrane –> more water reabsorption, restores blood volume
describe oxytocin’s first effect and its mechanism
kinetic hormone during childbirth - stimulates uterine smooth muscle to aid in childbirth
at term, baby in position, uterus smooth muscle is stretched –> this stretch sends neural signals to hypothalamus & causes paraventricular nucleus to synthesize & secrete oxytocin –> oxytocin causes uterine smooth muscle to contract & propel baby thru canal –> the more the uterus contracts, the stronger the signals are sent to hypothalamus –> more oxytocin released, so more contractions (positive feedback, amplification)
baby also produces oxytocin…
oxytocin also acts on second target tissue besides uterine smooth muscle…
baby also produces some oxytocin at end of term which enhances the whole uterine smooth muscle mechanism
oxytocin acts on placenta –> stimulates placenta to synthesize & secrete prostaglandins –> these act to increase uterine smooth muscle contraction
describe specific mechanism of how oxytocin works to stimulate uterine smooth muscle contraction
oxytocin binds to receptor, activates set of G proteins –> G proteins activate enzyme phospholipase C –> converts membrane phospholipid to 2 products, IP-3 & DAG –> IP-3 interacts with its own receptor to activate a calcium channel on SR, releasing calcium which initiates smooth muscle contraction
describe oxytocin’s second effect and its mechanism
stimulating mammary gland smooth muscle to aid in milk ejection during nursing
mom looking at baby is enough to produce 2nd oxytocin release –> enhanced by neural signals by nerves in nipples, feeds back to hypothalamus –> stimulates paraventricular nucleus –> 2nd wave of oxytocin targets mammary gland smooth muscle –> contraction & milk ejection
why does first pulse of oxytocin that effects uterine gland smooth muscle not have an effect on mammary gland smooth muscle?
depends on regulation of oxytocin receptors - oxytocin receptors remain low during most of pregnancy, but rapidly upregulated at end of term, 1st set upregulated are for uterine smooth muscle near time of birth
mammary gland smooth muscle is upregulated much more slowly and does not reach peak until after childbirth
after childbirth, uterine smooth muscle receptors are downregulated, but oxytocin receptors on mammary gland smooth muscle remain high
2nd pulse of oxytocin for mammary gland smooth muscle will also have an effect on…
uterine smooth muscle –> helps to contract uterus back to normal size & shape and helps to expel placenta
do males make oxytocin?
yes, oxytocin other function also effects the nervous system and responds to varying stimuli
oxytocin receptors found in nose, plays a role in responding to diff olfaction (especially memories associated with smells)
oxytocin release also plays role in creating bonding b/w mother and child
- also released during sex & creates parabonding
- also during social interactions, also sedation to calm down
