hypothalamus, obesity and eating

Question 1

describe the dual centre model for regulating feeding

Answer 1

two parts of the hypothalamus are responsible for two different functions
lateral hypothalmus: feeding centre (lesioned –> emancipated)
ventral medial hypothalamus: satiety centre (lesioned - fat)

Question 2

describe lipostatic theory

Answer 2

that they body and brain interact to maintain a constant body weight via leptin

Question 3

how is leptin produce

Answer 3

by ob gene, expressed in adipocytes

Question 4

how does leptin relate to fat

Answer 4

circulates in bloodstream in proportion to fat mass

Question 5

effects of leptin?

Answer 5

• -> decreased glucose, hence decreased insulin and bw

- ->increaesd temp and metabolic rate.

Question 6

what are the anorexigenic nt’s

Answer 6

POMC CART

Question 7

what are the orexigenic nt’s

Answer 7

NPY AgRP

Question 8

where are (an)orexigenic neurons located

Answer 8

arcuate nucleus in hypothalamus

Question 9

what happens when body weight increases?

Answer 9

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

Question 10

what happens as body weight decreases?

Answer 10

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

Question 11

what are the short term orexigenic signals?

Answer 11

ghrelin

Question 12

what are the short term anorexigenic signals?

Answer 12

insulin
leptin
CKK
amylin

Question 13

describe set point theory

Answer 13

weight returns to set point

Question 14

2 studies relating to set point theory?

Answer 14

1. 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
2. started for 10 weeks, then placed on normal diet. body weight, hence leptin, CCK, amylin decreased then increased. hunger and ghrelin increased then decreased.

Question 15

describe hedonistic eating

Answer 15

eating is reliant on reward pathways - reward pathways are split into liking and wanting

Question 16

define liking

Answer 16

affective: you enjoy eating something

Question 17

describe liking pathways

Answer 17

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.

Question 18

define wanting

Answer 18

motivational: leads to you actually eating

Question 19

describe wanting pathway

Answer 19

dopaminergic neurons extend from ventral tegmental area to basal forebrain.
-lesions result in aphagia, but no change to liking