Appetite

Question 1

what is the most potent stimulus of thirst?

Answer 1

plasma osmolality increase

Question 2

what are less potent stimuli of thirst?

Answer 2

blood volume reduction

blood pressure reduction

Question 3

what hormone is important for the regulation of osmolality?

Answer 3

ADH (vasopressin)

Question 4

main physiological action of ADH

Answer 4

acts on kidneys to transport aquaporin 2 channels to the collecting duct membrane > reabsorption of water

Question 5

low plasma ADH produces what urine?

Answer 5

large, dilute volumes

Question 6

high plasma ADH produces what urine?

Answer 6

small, concentrated volumes

Question 7

where in the hypothalamus are osmoreceptors found?

Answer 7

subfornical organs

organum vasculosum of the lamina terminalis

Question 8

osmoreceptor response to more concentrated plasma

Answer 8

cells shrink > ^proportion of cation channels > membrane depolarises > sends signals to ^ADH > fluid retention, invokes drinking
AND VICE VERSA

Question 9

when is thirst decreased after drinking?

Answer 9

decreased even before sufficient water has been absorbed by the GI tract to correct plasma osmolality

Question 10

receptors involved in thirst are found where?

Answer 10

mouth
pharynx
oesophagus

Question 11

is relief of thirst sensation via receptors in the mouth, pharynx, oesophagus short lived or long acting?

Answer 11

short lived

Question 12

when is thirst completely satisfied?

Answer 12

once plasma osmolality is decreased or blood volume or arterial pressure corrected

Question 13

effect of RAAS on blood pressure/volume

Answer 13

angiotensin II > ADH secretion, vasoconstriction, ^ sympathetic activity, thirst, (aldosterone release > H20 retention via electrolytes)

Question 14

aldosterone is released from where?

Answer 14

zona glomerulosa of adrenal cortex

Question 15

effect of aldosterone on electrolytes

Answer 15

Na+ absorption

K+ excretion

Question 16

effects of a reduction in fat mass

Answer 16

increases food intake and reduces energy expenditure

Question 17

effects of adipose tissue expansion

Answer 17

reduces food intake and increases energy expenditure

Question 18

what mechanism defends against reduction of body fat?

Answer 18

central circuit

Question 19

what molecules/hormones are involved in appetite regulation?

Answer 19

ghrelin
PYY
gut hormones
leptin

Question 20

briefly outline the structures of the hypothalamus

Answer 20

arcuate nucleus
paraventricular nucleus
lateral hypothalamus
ventromedial hypothalamus

Question 21

what is the arcuate nucleus involved in?

Answer 21

regulation of food intake

Question 22

how does the arcuate nucleus have access to peripheral hormones?

Answer 22

incomplete blood brain barrier

Question 23

the arcuate nucleus has what two neuronal populations?

Answer 23

Stimulatory (NPY/Agrp neuron)

Inhibitory (POMC neuron)

Question 24

neurons in the arcuate nucleus give feedback to?

Answer 24

paraventricular nucleus

Question 25

the melanocortin system

Answer 25

POMC > alpha-MSH > MC4R | Agrp >Agrp > MC4R

Question 26

what human CNS mutation affect appetite?

Answer 26

POMC deficiency | MC4-R mutation

Question 27

what signals from other brain regions affect appetite?

Answer 27

higher centres amygdala other parts of hypothalamus e.g. lateral hypothalamus vagus > brain stem > hypothalamus

Question 28

adipostat mechanism

Answer 28

circulating hormone produced by fat > sensed by hypothalamus > alter neuropeptides to increase or decrease food intake

Question 29

where is leptin made?

Answer 29

adipocytes in white adipose tissue

Question 30

main physiological actions of leptin

Answer 30

acts on hypothalamus regulating appetite (intake) | thermogenesis (expenditure)

Question 31

what is condition involving leptin?

Answer 31

congenital leptin deficiency

Question 32

mechanism of action of leptin

Answer 32

leptin > receptor (LRb) in the brain > regulate energy balance and neuroendocrine function. LRb signaling via STAT3 and a number of other pathways is required for the totality of leptin action.

Question 33

levels of leptin when body fat is low

Answer 33

low

Question 34

levels of leptin when body fat is high

Answer 34

high

Question 35

leptin in obesity

Answer 35

leptin resistance > hormone is present but doesn't signal effectively

Question 36

is leptin a viable weight control drug?

Answer 36

no, ineffective

Question 37

GI hormones are secreted from?

Answer 37

enteroendocrine cell in the stomach, pancreas and small bowel

Question 38

list GI hormones that regulate appetite

Answer 38

Ghrelin | Peptide YY

Question 39

effect of ghrelin

Answer 39

stimulates appetite | increases gastric emptying

Question 40

effect of peptide YY

Answer 40

inhibits food intake

Question 41

when are blood levels of ghrelin highest?

Answer 41

before meals

Question 42

how does ghrelin help prepare for food intake?

Answer 42

increases gastric motility | increases acid secretion

Question 43

effect of ghrelin on neurons in arcuate nucleus

Answer 43

stimulates NPY/Agrp neurons | inhibits POMC neurons

Question 44

apart from appetite regulation, ghrelin has a role in?

Answer 44

regulation of reward taste sensation memory circadian rhythm

Question 45

PYY is released from?

Answer 45

terminal ileum | colon

Question 46

PYY is released in response to?

Answer 46

in response to feeding

Question 47

effects on PYY

Answer 47

reduces appetite

Question 48

PYY inhibits what?

Answer 48

inhibits NPY release

Question 49

PYY has what effect on neurons in the arcuate nucleus?

Answer 49

stimulates POMC neurons

Question 50

obesity is associated with what comorbidities?

Answer 50

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

Question 51

describe the global trend of obesity and related comorbidities

Answer 51

increasing worldwide