Appetite

Question 1

the body regulates/controls thirst through which main triggers?

Answer 1

body fluid osmolality
blood volume is reduced
blood pressure is reduced

Question 2

why is plasma osmolality the most potent stimulus in thirst

Answer 2

change of 2-3% induces strong desire to drink

- 10-15% decrease in blood vol/pressure required to produce same response

Question 3

what is the role of adh in thirst and osmolality

Answer 3

acts on collecting duct in kidneys - aquaporin 2 channels

and regulates olume and osmolality of urine

Question 4

what is water diuresis

Answer 4

when plasma ADH is low and water is excreted

Question 5

what is anti diuresis

Answer 5

when plasma ADH is high, small volume of urine is excreted

Question 6

where is adh stored

Answer 6

posterior pituitary gland

Question 7

what are osmoreceptors

Answer 7

sensory receptors
responsible for osmoregulation
found in the hypothalamus

Question 8

which regions of hypothalamus are osmoreceptors found?

Answer 8

organum vasculosum of lamina terminalis

subfornical organ

Question 9

how do osmoreceptors regulate adh release

Answer 9

cells shrink when plasma is more concentrated
proportion of cation channels increases - membrane depolarises
sends signals to adh producing cells
fluid retention invokes drinking

Question 10

when is thirst completely satisfied

Answer 10

once plasma osmolality is decreased/ blood vol/arterial pressure is corrected

Question 11

what happens in kidneys when blood pressure drops

Answer 11

juxtaglomerular apparatus secretes renin which activates angiotensin system by cleaving angiotensinogen to angiotensin1 which is converted to angiotensin2 by ACE

Question 12

What are the effects of angiotensin 2

Answer 12

induces thirst

most important effect is on aldosterone

Question 13

what is the role of aldosterone

Answer 13

influences reabsorption of sodium and potassium excretion influencing water retention

Question 14

what is role of angiotensin 2

Answer 14

vasoconstriction - increases sympathetic activity

adh secretion

Question 15

what 2 gut hormones are involved in peripheral signalling in appetite regulation

Answer 15

ghrelin
pyy
- travels through vagus nerve which connects to brainstem which communicates with hypothalamus - cns e.g amygdala

Question 16

what is the long term hormones involved in appetite regulation

Answer 16

leptin

Question 17

what is orexigenic

Answer 17

appetite stimulant

Question 18

what is anorectic

Answer 18

appetite suppressive

Question 19

what does the lateral hypothalamus produce

Answer 19

orexigenic petides

Question 20

what is the ventromedial hypothalamus associated with

Answer 20

satiety

- lesions can lead to severe obesity

Question 21

when does food intake decrease

Answer 21

when arcuate nucleus pro opio melanocortin neurones activate

Question 22

what are some other hypothalamic factors which implicate appetite regulations

Answer 22

endocannabinoids
amp - activated protein kinase
protein tyrosine phosphotase

Question 23

what is the arcuate nucleus

Answer 23

brain area involved in regulation of food intake
incomplete bbb - allows access to peripheral hormones
- integrates peripheral and central feeding signals

Question 24

what are the 2 neuronal populations in the arcuate nucleus

Answer 24

stimulatory - NPY/agrp neuron

inhibitory - pomc neurone

Question 25

where are npy/agrp neurones found

Answer 25

only in arcuate nucleus in hypothalamus

Question 26

what is the role of npy/agrp neurones

Answer 26

potentially stimulate food intake by increasing neuropeptide y signalling and reducing melanocortin signalling

Question 27

what is agrp

Answer 27

endogenous melanocortin receptor antagonist

Question 28

what effect does leptin have on npy/agrp

Answer 28

inhibitory effects

Question 29

what effect does leptin have on pomc/cart

Answer 29

stimulatory effects

Question 30

what conditions can cause increased food intake via leptin mechanism

Answer 30

fasting uncontrolled diabetes genetic leptin deficiency

Question 31

other than feeding what are 2 factors the arcuate nucleus is responsible for

Answer 31

fertility and cardiovascular regulation

Question 32

what is the central melanocortin system

Answer 32

collection of central nervous circuits e.g npy/agrp and pomc

Question 33

what is melanocortin

Answer 33

product of pomc gene

Question 34

what are some human cns mutations affecting appetite

Answer 34

no npy/agrp mutations associated with appetite - pomc deficiency and mc4r mutations cause morbid obesity - mutations not responsible for obesity - but useful to explain signalling

Question 35

what is the adipostat mechanism

Answer 35

circulating hormone produced by fat | - hypothalamus senses concentration of hormone and then alters neuropeptides to increase/decrease food intake

Question 36

what is leptin

Answer 36

hormone made by adipocytes in white adipose tissue and enterocytes circulates in plasma acts on hypothalamus regulating appetite and thermogenesis

Question 37

what is congenital leptin deficiency

Answer 37

rare condition | causes severe obesity very early in life

Question 38

what is leptin resistance

Answer 38

leptin circulates in plasma in conc proportional to fat mass obesity due to leptin resitance leptin is ineffective as weight control drug

Question 39

why do we feel less hungry after a meal

Answer 39

hormone signals from gut aka gi hormones

Question 40

what are gi hormones secreted by

Answer 40

enteroendocrine cells in stomach, pancreas and sb

Question 41

what gi hormones is appetite regulated by

Answer 41

ghrelin - stimulates appetire, increases gastric emptying | peptide yy - inhibits food intake

Question 42

what is ghrelin

Answer 42

*help prepare food intake by increasing gastric mobility and acid secretion directly modulates neurones in arcuate nucleus stimulates npy/agrp neurones inhibits pomc neurones - increases appetite - regulation of reward, taste sensation, memory and circadian rhythm

Question 43

what is peptide tyrosine tyrosine

Answer 43

short peptide released in terminal ileum and colon in response to feeding reduces appetite food arriving at ti and colon results in pyy release inhibits npy release stimulates pomc neurones

Question 44

what cormobidities is obesity associated with

Answer 44

``` depression sleep apnoea bowel cancer stroke mi osteoarthiritis peripheral vascular disease gout hypertension diabetes ```