Appetite

Question 1

how does the body control thirst?

Answer 1

body fluid osmolality increase (most potent stimulus)
Blood vol reduced
Blood pressure reduced

Question 2

What is ADH?

Answer 2

Also known as vasopressin - act on collecting duct in kidney on aquaporin 2 channels - increased water absorption

Question 3

What is water diuresis?

Answer 3

Plasma ADH is low = large vol of water excreted

Question 4

What is anti diuresis?

Answer 4

Plasma ADH is high = small vol of urine excreted

Question 5

where is ADH stored?

Answer 5

posterior pituitary gland

Question 6

How does the body measure osmolality?

Answer 6

Osmoreceptors - v sensitive to changes in blood osmolality

Question 7

Where are the osmoreceptors found?

Answer 7

Organum vasculosum of the lamina terminalis

subfornical organ

Question 8

How to osmoreceptors lead to ADH release?

Answer 8

Plasma more conc = cells shrink = proportion of cation channels increases so membrane depolarises = sends signal to ADH producing cells = ADH released

Question 9

What affect does ADH have?

Answer 9

increased fluid retention

Question 10

Where are the receptors that detect thirst?

Answer 10

mouth/ pharynx/ oesophagus

Question 11

How is BP/ vol controlled?

Answer 11

Drop in BP causes release of renin from kidneys = renin cleaves angiotensin 1 to 2 which has effects on the body to combat

Question 12

what does angiotensin 2 do?

Answer 12

Increases in sympathetic activity leading to vasoconstriction

induces thirst

Release of aldosterone

Question 13

what does aldosterone do?

Answer 13

water retention via sodium/ chloride absorption an potassium excretion

Question 14

How does weight homeostasis work?

Answer 14

central circuit defends against the reduction or rapid expansion of adipose tissue (body wants to go back to original form from the overfed or underfed state)

Question 15

Where is appetite regulates

Answer 15

hypothalamus

Question 16

Which hormones affect appetite

Answer 16

Ghrelin + other gut hormones
LEPTIN

• neural input from the periphery + other brain regions

Question 17

What two things contribute to being in an overfed or underfed state?

Answer 17

Energy expenditure

Food intake

Question 18

what is the arcuate nucleus?

Answer 18

Neurones in medial basal part of hypothalamus - releases appetite suppressive + stimulants

Question 19

what is an appetite suppressive called?

Answer 19

Anorectic

Question 20

what is an appetite stimulant called?

Answer 20

Orexigenic

Question 21

what is the paraventricular nucleus?

Answer 21

Neurones which project to posterior pituitary (where ADH is stored) = release ADH + oxytocin

Question 22

How does the arcuate ncleus have access to peripheral hormones

Answer 22

blood brain barrier is incomplete - allows access

Question 23

What are the two populations in the arcuate nucleus

Answer 23

POMC neurone (inhibitory)
NOY/ Agrp neurone (stimulatory)

Question 24

How do NOY/ Agrp neuron stimulate appetite?

Answer 24

Increases NPY signalling + reducing POMC signalling via increase of Agrp

Question 25

How does leptin affect neurones in hypothalamus

Answer 25

Receptors - leptin inhibits NPY/ AGRP + stimulates POMC (decreased food intake)

Question 26

Explain the melanocortin system?

Answer 26

Increase in Agrp in arcuate nucleus inhibits MC4R in paraventricular nucleus/ increase in POMC stimulates MC4R release (MC4T decreases food intake)

Question 27

Which mutations can affect appetite

Answer 27

No NPY/ Agrp mutations POMC deficiency/ MC4R mutations can cause morbid obesity Not responsible for prevalence of obesity however

Question 28

what is the adipostat mechanism

Answer 28

hypothalamus alters neuropeptide to increase/ decrease food intake according to hormone level released by adipose tissue

Question 29

what is leptin?

Answer 29

made by adipocytes + enterocytes | Acts on hypothalamus regulating intake + expenditure

Question 30

congenital leptin deficiency

Answer 30

Very rare | causes severe obesity very early in life (constantly hungry due to no appetite control)

Question 31

What is the level of leptin when low body fat?

Answer 31

Leptin is low

Question 32

What is the level of leptin when high body fat?

Answer 32

Leptin is high

Question 33

what is leptin resistance

Answer 33

leptin doesn't signal effectively so appetite + thermogenesis control does not work

Question 34

Leptin as a drug?

Answer 34

DOES NOT WORK as a weight control drug

Question 35

Why do we feel less hungry after a meal?

Answer 35

Gastrointestinal hormones like ghrelin and peptide YY

Question 36

Where are gastrointestinal hormones released

Answer 36

Gastrointestinal hormones secreted by enteroendocrine cells in stomach/ pancreas/ small bowel

Question 37

what does ghrelin do?

Answer 37

Increases appetite by increasing gastric motility + acid secretion

Question 38

how do concentrations of ghrelin change in a day?

Answer 38

increases two fold before meal times/ follows diurnal cycle

Question 39

what does peptide YY do?

Answer 39

Reduces appetite | Inhibits NPY release

Question 40

Comorbidities associated with obesity

Answer 40

Cardiovascular - stroke/ MI/ hypertension etc Osteoarthritis/ gout Sleep apnoea Depression