alimentary mechanisms

Question 1

what do sensing organs in hypothalamus detect

Answer 1

circulating gut and appetite regulation hormones

Question 2

how do sensing organs in hypothalamus detect concentration of circulating gut and appetite regulation hormones

Answer 2

many regions have incomplete blood brain barrier

Question 3

how does the hypothalamus elicit a coordinate central response to oversee energy balance, and why have this many

Answer 3

combines peripheral signals (neural input, grehlin, peptide YY, leptin, other gut hormones); many signals as redundancy (make sure if one neuronal population or gene doesn’t work to allow compensation) and different causes (e.g. nausea vs full of food)

Question 4

what 2 nuclei in hypothalamus are involved in fundamental central control of appetite regulation

Answer 4

acruate (bottom of brain) and paraventricular

Question 5

where is the arcuate nucleus located

Answer 5

base of brain

Question 6

what allows peripheral signals to directly activate the arcuate nuclei circuitry

Answer 6

peripheral signals such as nutrients, hormones, concentrations and temperature

Question 7

what are the 2 separate neuronal populations within the arcuate nucleus

Answer 7

NPY/Agrp (neuropeptide Y/Agouti-related peptide) and POMC (proopiomelanocortin)

Question 8

which neurone stimulates food intake, and which neurone inhibits it

Answer 8

NPY/Agrp stimulates, POMC inhibits

Question 9

where are NPY/Agrp and POMC neurones located

Answer 9

NPY/Agrp located medially, POMC located laterally

Question 10

where are the somas of these neurones

Answer 10

acruate nucleus

Question 11

where do the axons from these neurones project for appetite

Answer 11

paraventricular nucleus and other regions of brain

Question 12

how do POMC neurones reduce food intake

Answer 12

a-MSH (a melanocyte stimulating hormone) from POMC neurones binds to MC4R (melanocortin 4 receptor) receptor, agonising receptor

Question 13

how to NPY/Agrp neurones maintain food intake behaviour

Answer 13

Agrp from NPY/Agrp neurones binds to MC4R receptor, antagonising it and blocking satietal signal

Question 14

what are released to bind receptors in paraventricular nuclei

Answer 14

neuropeptides

Question 15

what deficiency and mutation can cause morbid obesity (not usually responsible)

Answer 15

POMC deficiency and MC4R mutation

Question 16

what do other brain input signals into paraventricular nuclei include

Answer 16

higher centres, amygdala (emotion, memory), other parts of hypothalamus (e.g. lateral), vagus to brain stem to hypothalamus

Question 17

what does leptin provide

Answer 17

long term appetite regulation

Question 18

what secretes leptin

Answer 18

cells in white adipose tissue

Question 19

what happens when leptin binds to receptors in hypothalamic circuits

Answer 19

suppresses appetite (stimulates anorexigenic behaviours) and increases energy expenditure (thermogenesis)

Question 20

evolutionary premise of leptin (adipostat mechanism)

Answer 20

well-nourished adult accumulates body fat, which increases leptin secretion and suppresses appetite

Question 21

what is absent leptin, regulatory defect and leptin resistance in hypothalamus associated with

Answer 21

obesity; if high fat diet can cause leptin resistance (massive stimulation of appetite) which cannot be cured with leptin

Question 22

what secretes ghrelin and when

Answer 22

cells in stomach in build up to meal

Question 23

function of ghrelin

Answer 23

binds to hypothalamic receptors and increases short-term perception of hunger and urge to eat (stimulates NPY/Agrp neurones and inhibits POMC neurones)

Question 24

what secretes peptide YY 3-36

Answer 24

cells in ileum and colon in response to meal

Question 25

function of peptide YY 3-36

Answer 25

binds to hypothalamic receptors and reduces short-term perception of hunger and urge to eat (inhibits NPY release and stimulates POMC neurones)

Question 26

what is cleaved off in peptide YY when full

Answer 26

first two amino acids

Question 27

future of obesity treatment

Answer 27

gut hormones targeting only relevant circuits which are released daily without side-effects

Question 28

comorbidities of obesity

Answer 28

depression, stroke, MI, sleep apnoea, hypertension, osteoarthritis, bowel cancer, peripheral vascular disease, gout