apetite Flashcards
what is osmolality and why we use it over osmolarity
Body fluid osmolality : solute concentration in 1kg vs osmolarity in one mol so osmolality more clinically relevant
what are the stimuli that tell the body we are thirsty and which is the most potent
body fluid osmolality
decreased blood volume
reduced bp
what hormone regulates osmolality? organ and specific site of action
ADH- Acts on the kidneys to regulate the volume & osmolality of urine
Collecting duct - Aquaporin 2 channel
action of ADH- SO EXPLAIn when high vs when low
When plasma ADH is low a large volume of urine is excreted (water diuresis)
When plasma ADH is high a small volume of urine is excreted (anti diuresis)
where is ADH STORED
posterior pituitary
how does our body measure osmolality and what does it do about it
Sensory receptors
Osmoregulation
Found in the hypothalamus
how do osmoreceptors stimulate ADH release and thirst
1) cells shrinK when plasma more concentrated BC fluid moves out
2) more cation channels open (as a direct result of shrink- mechanically they are pushed to open see slide 9)
3) membrane depolarizes
4) sends signal to ADH producing cells to incr ADH
5) fluid retention invokes drinking
what happens to our sensation of thirst when we first drink water and how?
Thirst is initially decreased temporarily due to
Receptors in mouth, pharynx, oesophagus are involved
when is thirst completely satisfied?
once plasma osmolality has decreased or blood volume or arterial pressure corrected.
how is the renin angiotensin aldosterone system involved in blood pressure/ volume changes
juxtaglomerular cells sense drop in BP and convert pre-renin to renin in kidney
then renin converts angiotensinogen to angiotensin I in the liver
then ACE converts angiotensin I to angiotensin II in the lungs
ANGIOTENSIN II does all the things to fix the issue of low water in body…
Angiotensin II actions to ensure high osmolality drops
1) increase thirst
2) aldosterone release from adrenal cortex which increases h2o retention via nacl absorption and K excretion in kidneys
3) vasoconstriction by increasing sympathetic activity
4) ADH secretion
are adults more likely to fluctuate weight a lot if they dont put consious effort to balance their intake and expenditure?
no. in general most adults maintain stable weight over long periods
based on body weight homeostasis principles what are the homeostatic processes that occur when fat mass incr and decr
when fat incr food expenditure decr and energy expend incr and sympathetic nervous system activity incr!!!
aiming to loose weight
and opposite for fat decr
aim to regain weight
What system(s) defend against rapid expansion of body weight?
Yet to be discovered
what is the main brain area involved in appetite regulation
hypothalamus controls food intake and energy expenditure
