11 Regulation Of Appetite Flashcards
What triggers thirst and which one is the most potent stimulus
Increased of osmolarity
Blood volume reduces
Blood pressure reduces
Plasma osmolarity is the most potent stimulus - 2-3% increase induced a strong response
The other two stimuli require 10-15% increase
Where are the osmoreceptors that trigger thirst and explain what is significant about these locations
Hypothalamus, OVLT (organum vasculosum) and SFO (subfornical organ) which the latter two are part of circumventricular organ
They are outside of blood brain barrier so are able to sense the change in blood plasma osmolarity
How does the change in plasma osmolarity cause the release of ADH
Osmoreceptors shrink to send signals for making ADH
What are the three responses that are responsible to regain plasma osmolarity
Thirst, release of ADH and angiotensin II
What effects do the osmoreceptors in mouth have on thirst
When the brain senses increased plasma osmolarity, the sensation of thirst can be relived temporarily with drinking sensed by the receptors in mouth, pharynx and oesophagus. But thirst is only completely satisfied when plasma osmolarity is corrected
What triggers angiotensin release and how does this regulate plasma osmolarity
Renin angiotensin system is activated when there is decrease in BP. Angiotensin II activates SFO neurons to stimulate thirst
Explain the neuronal organisation of hypothalamus and their neurotransmitters (and their receptors) involved in regulating food intake
Superoinferiorly: paraventrciular nucleus, lateral hypothalamus, ventromedial hypothalamus, 3rd ventricle, arcuate nucleus
Agrp/NPY neurone releases Agrp to stimulate hunger
POMC neurone releases a-MSH to stimulate satiety
Both of these neurotransmitters act on MC4R in paraventricular nucleus
What are the characteristics of obese patients with MC4R or POMC mutations
Red hair
Skin pigmentation
What is leptin and where is it released from and what does it do
167 amino acid produced from white adipocyte to reduce food intake and increase thermogenesis by acting upon the hypothalamus
Which pathways of leptin can go wrong to cause obesity? Can we use this to solve the problem with increasing obesity prevalence in the world
Absent leptin
Regulatory defect
Leptin resistance
No, because most obese people are with leptin resistance evidenced from the fact obese patients express high levels of leptin. However there is a small proportion of congenital defect lacking leptin which mean they are sensitive to treatment supplying them with leptin
What is PYY in terms of its origin of release, its effect and signalling pathway in both non-truncated and truncated form
It is a 36 amino acid. It is released from terminal ileum, colon and rectum.
Non truncated: reduces GI secretion, gall bladder contraction and motility
Truncated (PYY3-36) signals to the hypotalamus to increase POMC activity and inhibit NPY to decrease appetite
What is ghrelin in terms of its structure, function
It is a 28 amino acid peptide with fairy acid chain attached to Ser3 for it to get in different tissues to bind receptors
It stimulates hunger by activated N and inhibiting POMC
