hypothalamus, obesity and eating Flashcards
describe the dual centre model for regulating feeding
two parts of the hypothalamus are responsible for two different functions
lateral hypothalmus: feeding centre (lesioned –> emancipated)
ventral medial hypothalamus: satiety centre (lesioned - fat)
describe lipostatic theory
that they body and brain interact to maintain a constant body weight via leptin
how is leptin produce
by ob gene, expressed in adipocytes
how does leptin relate to fat
circulates in bloodstream in proportion to fat mass
effects of leptin?
- -> decreased glucose, hence decreased insulin and bw
- ->increaesd temp and metabolic rate.
what are the anorexigenic nt’s
POMC CART
what are the orexigenic nt’s
NPY AgRP
where are (an)orexigenic neurons located
arcuate nucleus in hypothalamus
what happens when body weight increases?
leptin increases.
this stimulates anorexigenic nt’s (POMC CART), which turns off lateral hypothalamus (feeding centre), and turns on PVN pathway (CRH, TRH) –> fat burning.
also food seeking behaviour decreased, increased sympathetic arousal to sites involved in energy expenditure
what happens as body weight decreases?
decreased leptin
orexigenic neurons in arcuate nucleus (NPY AgRP) activate lateral hypothalamus (stimulate feeding), turn off PVN pathways
increased feeding behaviour
decreased sympathetic arousal to sties involved in energy expenditure
what are the short term orexigenic signals?
ghrelin
what are the short term anorexigenic signals?
insulin
leptin
CKK
amylin
describe set point theory
weight returns to set point
2 studies relating to set point theory?
- after weight loss, actual energy expenditure < predicted energy expenditure (trying to get weight back to normal)
after weight gain, actual energy expenditure > preducted energy expenditure - started for 10 weeks, then placed on normal diet. body weight, hence leptin, CCK, amylin decreased then increased. hunger and ghrelin increased then decreased.
describe hedonistic eating
eating is reliant on reward pathways - reward pathways are split into liking and wanting
define liking
affective: you enjoy eating something
describe liking pathways
neurons from brainstem synapse with neurons in nucleus accumbens; brainstem neurons release mu opoids which bind to NA, leading to liking of sweet/high fat foods.
define wanting
motivational: leads to you actually eating
describe wanting pathway
dopaminergic neurons extend from ventral tegmental area to basal forebrain.
-lesions result in aphagia, but no change to liking
