Appetite regulation Flashcards
What conditions lead a person to feel thirst?
Change in blood volume, reduction of blood pressure and changes in body fluid osmolarity (that’s the main one on day to day)
What is an important hormone in terms of thirst regulation?
ADH/Vassopression, which when water is low will cause reabsorption. If plasma ADH is low-large volume of urine. Decrease osmolality means DECREASED ADH
ADH causes thirst
What cells detect osmolarity for ADH release?
Osmoreceptors, in hypothalamus, OVLT and SFO-cells shrink and swell is response to the osmololality. Signal down to ADH hypothalamic neclei (neurohypphysis)
These organs are not entirely protected by the blood brain barrier-and can allow proper sensing
What causes short term relief of thirst?
Thrist is decrease by drinking evem before the to correct plasma is reached-mouth, parynx, have receptors BUT this relief is short lived-only relieved with right osmo
What is the role of RAAS system in thrist?
Angiotensiogen to Angio 1 by renin, then 2 by Ace, then to adrenals-release aldosterone-re-intake salt which brings water too
Angiotensin II also evokes a sensation of thirst-and SFO neurons
What is a general descrintpion of body weight homeostasis?
Ghrelin, PYY and other hormones, neural input and leptin => hypothalamus => decide their food intake and energy expenditure
How do hunger signals integrate in the brain?
Signals send to hypothalamus-Leptin from white adipose tissue, PYY from gut act of POMC (inhibitory) neuron. Ghrelin from stomach to AGrP (activatory) neuron. Both these are from neurones in arcuate nucleus-and then communicate to hypothalamus
Amylin from pancrease and CNTF-skeletal muscle go directly to hypothalamic
The hypothalamus then communicates to higher centres
What is the arcuate nucleus?
Hypothalamus has several regions- paraventricular regions in center, lateral and ventromedial on either sides. And at the bottom, arcuate nucleus
What does the arcuate nucleus contain?
Incomplete blood barrier-allow hormone
2 populations of neurons: Stimulatory (NPY/AGRP) and Inhbitory population (POMC)
(POMC is cut differently in hypothalamus)
2 pops are completely separate
What is the role of the arcuate nucleus?
Circulating factors bind the neurons (POMC/NPY)-the cell bodies are in the arcuate nuceleus, but their axons go to the hypothalamus (even sometimes directly to higher center)
Also can decide on some adrenohypohysis releases
Describe the melanocortin system?
Food intake is importat to MC4R in paraventricular nucleus
POMC is cut to alpha-MSH-and that activates the MC4R-decrease food intake
On the other side, Agrp acts as a inhibitor (competitive inhbit) to the receptor, so when youre hundry, agrp is blocking MC4R activation-you are hungry
What mutations to the melanocortin stystem exist in humans?
No NPY or Agrp mutations found. But POMC deficiency (also Ginger) or MC4R cause morbid obesity What other brain regions are part of appetite regulation? Higher centres (for diet, etc), amygdala (emotions, memory), other parts of lateral hypothalamus. Vagus to brain stem to hypothalamus-
What is Leptin?
A 167aa hormone-long term regulation of appetite
Made by adipocytes in adipose tissue, so as you grow fatter, more adipocytes and fatter. Circulated in plasma. Lectin singals to hypothalamus Low fat means low leptin and HIGH appetite (also increases thermogenesis
What is the role of leptin in obesity?
Its leptin resistance-they have high leptin but the resistance means its not signalling to eat less
Unsure if it develops or born with but fat diet for a while decreases sensitivity
There are few cases of leptin deficient people-always hungry
What are the main reason why you don’t feel hungry after a meal?
stretch receptors play a role and can override if too much, but released hormones are the main one
What is Peptide YY (in terms of appetide regulation)
PYY 38aa. Cleave last 2 aa during eating, making PYY3-36-which diminishes appetide
the release of PPY peaks after a meal-around 100 minutes, and is proportional to how much you take in
PPY inhbitits NPY and stimulates POMC-
giving some to humans reduce food intake
