20. 21. Physiological Control of Eating; Diet, Disease and Obesity

Question 1

Control of food intake in 3 words

Answer 1

Hunger, appetite and satiety

Question 2

What are the biological drives of hunger?

Answer 2

Empty stomach’s mechanoreceptors

Stomach releasing ghrelin

Low levels of circulating nutrients

Question 3

What are the biological drives of satiety?

Answer 3

Opposite of hunger

Release of CCK, GIP, GLP-1 and PYY by the intestines

Insulin stimulates release of leptin from adipocytes

Question 4

Short term feeding influences

Answer 4

Signals to brainstem via vagus nerve from stretch, chemo and peptide hormone receptors

In the liver and GI tract

Question 5

Long term feeding influences

Answer 5

Controlled by the brain plus insulin, leptin, ghrelin, PYY from the GI tract

Question 6

Explain CNS control of food intake

Answer 6

Neural mechanisms in hypothalamus

LHA causes food intake if stimulated (known as the feeding centre)

Question 7

In terms of CNS control of cessation of food intake

Answer 7

VMH causes cessation and even starvation if stimulated

Arcuate nucleus receives inputs from GI tract, hormones etc. to signal the centres via peptides

Question 8

State the hormones involved in short term mechanisms of controlling eating

Answer 8

Insulin and CCK suppress hunger

Glucagon and adrenaline stimulate hunger

Question 9

State the hormones involved in long term mechanisms of controlling eating

Answer 9

Leptin
Ghrelin
Insulin
Peptide YY

Question 10

What is ghrelin known as?

Answer 10

Hunger hormone

Feeding stimulant (orexigenic)

Peaks in the morning after slow increase overnight in healthy people

Question 11

Explain ghrelin secretion in relation to body weight

Answer 11

Inversely proportional

Losing weight results in hunger

Question 12

Where is PYY released from and when?

Answer 12

Ileum and colon

Following a meal

Question 13

What are the effects of PYY?

Answer 13

Slows gastric motility and emptying

Anorectic

Reduces ghrelin circulation

Increases energy expenditure and fat oxidation rates

Decreased in obese patients

Question 14

What is leptin known as?

Answer 14

Satiety signal

Question 15

What is leptin produced by?

Answer 15

Adipocytes

Question 16

What does leptin bind with to inhibit feeding?

Answer 16

Neurons in hypothalamus

Question 17

What is the relevance of “a-melanocyte stimulating hormone”?

Answer 17

Stimulates production of melanin in skin, acts as an appetite suppressor in the brain

Question 18

What is the relevance of neuropeptide-Y?

Answer 18

Highly orixergenic, involved in cognition, sexual function, vascular resistance, circadian rhythms

Question 19

Explain what is meant by “sensory specific satiety”

Answer 19

People/animals eat for longer when given a range of foods

Question 20

What is meant by palatability?

Answer 20

Dopamine - reward NT and also inhibits feeding.

Affected by palatability - volume of meals and composition

Question 21

Explain the effects of dopamine inhibitors on feeding and give an example

Answer 21

Decrease appetite by inhibiting dopamine reuptake

Cocaine

Question 22

What is serotonin’s role in eating behaviours?

Answer 22

Anorexigenic, reduces feeding

5-HT receptor antagonists reduce appetite

Question 23

What is BMR determined by other than body weight and activity levels?

Answer 23

Thyroid function

Question 24

How can BMR be measured?

Answer 24

Calorimetry in a temperate room

Question 25

What kind of drug is orlistat?

Answer 25

Pancreatic lipase inhibitor

Question 26

How does orlistat function?

Answer 26

Reduces fat absorption

Fewer TG’s broken down