Lec 13 - Food Intake Flashcards
3 pillars of food intake
- homeostasis
- reward/hedonic
- aversion
2 systems that control homeostatic control of food intake
> short term system:
- mechanosensation
- chemosensation
- hormone release
- neural activation
long term system:
- maintence of adequate fat stores over long time
(remember theyre both intergrated)
2 key components of energy balance
energy expenditure
energy intake
energy surfeit
weight gain
3 stages of short term homestatic
hunger
satitation (terminates individual meal)
satiety (fullness between meals)
what are the 4 gut hormones that control short term control food intake
- CCK
- GLP-1
- GIP
- Ghrelin
main adiposity signal
leptin
what is gut brain axis
flow of info between GI tract and CNS
orexigenic signal
stimulate feedback
anorexigenic signal
inhibit feedback
what are circumventricular organs (CVO)
structures that permit polypeptide hypothalamic hormones to leave the brain without disrupting the blood-brain barrier (BBB)
what part of hypothalamus are key anorexegnic/orexigenic signal
arcuate hormones
what do POMC neurons release
alpha-melanocyte stimulating hormone (aMSH)
= anorexigenic
3 main orexegnic hormones
ALL released by AgRP/NPY neurons
AgRP (agouti related peptide)
NPY (neuropeptide Y)
GABA (a neurotrans which inhibits POMC neurons)
what neurones does aMSH activate
MC4R neurons
what action does AgRP have
inverse agonist of MC4R
what does NPY do
inhibits PVH neurons
what does GABA do
inhibit POMC neurons
what is POMC cleaved by to make alphaMSH
PC1/3 and PC2
mutations in what are mongenic causes of obsesity in humans and rodents
POMC, PC1 or MCR4 (most common)
what is area postrema (AP)
a circumventricular organ
exposed to blood borne signals
what is Nucleus of the solitary tract (NTS)
recieves input front afferent vagus nerve fibres
= main hub for neuronal input from GI tract
what does the vago vagal circuit control
gastric motility
= if increased = enhanced hunger
how, via leptin, does adiposity effect food intake
increase adiposity = increase leptin = an anorexigenic hormone
- activates POMC
- inhibits AgRP/NPY hormones
what can chronic disruption of energy intake lead to
dysfunctional body weight:
e.g.
- obesity
- anorexia nervosa
- cancer induced cachexia
what are most forms of obesity caused by
caused by a multi-factorial genes x environment interaction creating an imbalance
between energy intake and energy expenditure
(but could be monogenic, see previous flashcard)
