Appetite

Question 1

What factors determine when we get thirsty?

Answer 1

Body fluid osmolality
Blood volume is reduced
Blood pressure is reduced

Question 2

Q. Which is the most potent stimulus?

Answer 2

Plasma osmolality increase is the more potent stimulus – change of 2-3% induces strong desire to drink
Decrease of 10-15% in blood volume or arterial pressure is required to produce the same response

Question 3

What regulates osmolality and where does it work?

Answer 3

Antidiuretic hormone (ADH) or vasopressin

Acts on the kidneys to regulate the volume & osmolality of urine
—-Collecting duct - Aquaporin 2 channel

Question 4

What happens when plasma ADH is low?

Answer 4

A large volume of urine is excreted (water diuresis)

Question 5

What happens when plasma ADH is high?

Answer 5

a small volume of urine is excreted (anti diuresis)

Question 6

Where is ADH stored?

Answer 6

posterior pituitary

Question 7

What are osmoreceptors? What is their function? Where are they found?

Answer 7

Sensory receptors
Osmoregulation
Found in the hypothalamus

Question 8

Which regions are these receptors found in the hypothalamus?

Answer 8

Organum vasculosum of the lamina terminalis (OVLT)

Subfornical Organ (SFO)

Question 9

How do osmoreceptors work to release ADH>

Answer 9

Question 10

How is thirst decreased? What receptors are involved? How is thirst completely satisfied?

Answer 10

-Thirst is decreased by drinking even before sufficient water has been absorbed by the GI tract to correct plasma osmolality
-Receptors in mouth, pharynx, oesophagus are involved
-Relief of thirst sensation via these receptors is short lived
-Thirst is only completely satisfied once plasma osmolality is decreased or blood volume or arterial pressure corrected.

Question 11

What are changes in blood pressure and volume controlled by?

Answer 11

The renin-angiotensin-aldosterone system

Question 12

How does the renin-angiotensin-aldosterone system work?

Answer 12

Question 13

What does a reduction in fat mass increase?

Answer 13

Food intake and reduces energy expenditure

Question 14

What does adipose tissue expansion reduce?

Answer 14

Food intake and increases energy expenditure

Question 15

What happens in overfed state during weight homeostasis?

Answer 15

Question 16

What happens in underfed state during weight homeostasis?

Answer 16

Question 16

What information does the hypothalamus take in during appetite regulation?

Answer 16

Question 17

What does the hypothalamus control in appetite regulation?

Answer 17

-Food intake
-Energy expenditure

Question 18

What is the appetite stimulating peptide?

Answer 18

Orexigenic

Question 19

What is the appetite suppressive peptide?

Answer 19

Anorectic

Question 20

What is the arcuate nucleus’s function?

Answer 20

Synthesises information leading to the production of orexigenic and anorectic neuropeptides

Question 21

Where is the arcuate nucleus?

Answer 21

Basal medial aspect of hypothalamus
Surrounding third ventricle

Question 22

Where does the arcuate nucleus pass information to?

Answer 22

Paraventricular nucleus and this has neurones that terminate in the posterior pituitary

Question 23

What does the lateral hypothalamus do?

Answer 23

Produces orexigenic neuropeptides

Question 24

What do AGRP neurones do?

Answer 24

Inhibits POMC

Question 25

What mutation can cause morbid obestiy?

Answer 25

POMC deficiency and MC4-R mutations cause morbid obesity.

Question 26

What is involved in the melanocortin system?

Answer 26

Question 27

What other brain regions send signals that are involved in appeitite?

Answer 27

Question 28

Explain the Adipostat mechanism

Answer 28

Question 29

Where is leptin made and where is it circulating? Where does it act and what does it do?

Answer 29

Made by adipocytes in white adipose tissue and enterocytes Circulates in plasma. Acts upon the hypothalamus regulating appetite (intake) and thermogenesis (expenditure).

Question 30

Explain the systemic effect of leptin?

Answer 30

Low when low body fat High when high body fat Replacement in the ob/ob mouse decreases weight Hormone that decreases food intake and increases thermogenesis

Question 31

Explain leptin resistance

Answer 31

Leptin circulates in plasma in concentrations proportional to fat mass Fat humans have high leptin Obesity due to leptin resistance- hormone is present but doesn’t signal effectively Leptin is ineffective as a weight control drug.

Question 32

Explain the mechanism of leptin

Answer 32

Question 33

Why do we feel less hungry after a meal?

Answer 33

Hormonal Signal from the gut

Question 34

Where are gastrointestinal hormones secreted from? What are their functions?

Answer 34

Enteroendocrine cells in the stomach, pancreas & small bladder Control various functions of digestive organs

Question 35

What does Ghrelin do?

Answer 35

Stimulate appetite, increases gastric emptying

Question 36

What does Peptide YY do?

Answer 36

Inhibits food uptake

Question 37

When is Ghrelin highest? What does it do? What neurones does it modulate?

Answer 37

Question 38

Why is PYY not a successful weight loss medication?

Answer 38

As the consequences are intolerable - nausea and vomitting

Question 39

What is PYY? Where is it released?

Answer 39

Question 40

What are the consequences of obesity?

Answer 40

Depression Sleep apnoea Bowel cancer Osteoarthritis Gout Stroke Myocardial infarction Hypertension Diabetes Peripheral vascular disease