11. Regulation of Appetite

Question 1

When does an individual perceive thirst?

Answer 1

1) Body fluid osmolarity is increased
2) Blood volume is reduced
3) Blood pressure is reduced

Question 2

What the more potent stimulus of thirst?

Answer 2

Body fluid osmolarity increasing

Question 3

What is the function of vasopressin/ADH?

Answer 3

It acts on the kidneys to regulate volume and osmolarlity of urine

Question 4

How is vassopressin release regulated?

Answer 4

By osmoreceptors - which detect changes in osmolarity

Question 5

Where are osmoreceptors found?

Answer 5

Hypothalamous
Organ vasculosum
Subfornical organ

Question 6

What are circumventricular organs?

Answer 6

Organs that are outside of the blood brain barrier or have an incomplete blood brain barrier

Question 7

How do the cells respond when the plasma is dilute?

Answer 7

They expand (vice versa)

Question 8

What happens when there is increased plasma osmolality?

Answer 8

Invokes drinking and ADH release
Increased ADH stimulates kidney to conserve water
Vice versa

Question 9

Where are the receptors responsible for the relief of thirst?

Answer 9

Receptors in the mouth, pharynx and oesophagus

The relief of thirst by these receptors are short lived

Question 10

What hormone evokes the sensation of thirst?

Answer 10

Angiotensin II

Question 11

What does angiotensin II activate?

Answer 11

The subfornical organ neurones

Question 12

What is the core priniciple behind thirst?

Answer 12

It all contributes to the homeostatic response to restore and maintain the body fluids at their normal level

Question 13

What is body weight homeostasis?

Answer 13

The balance between food intake and energy expenditure

Question 14

Where is energy intake and expenditure balanced?

Answer 14

Hypothalamous

Question 15

What information from the periphery is interpreted by the hypothalamous?

Answer 15

Hormones and neural input

Question 16

In terms of appetite what is the function of hypothalamous?

Answer 16

It judges how much food intake there should be compared to energy expenditure

Question 17

What is the function of the arcuate nucleus?

Answer 17

Regulation of food intake and integrates peripheral and central feeding signals

Question 18

What are the two neuronal populations of the arcuate nucleus?

Answer 18

Stimulates appetite
(NPY/Agrp neuron)
Inhibits appetite (POMC neuron)

Question 19

How does the arcuate nucleus have access to the perhipheral hormones?

Answer 19

It has an incomplete blood brain barrier

Question 20

What does NPY/Agrp affect?

Answer 20

It increases feeding - something in the blood binds to the receptors on neurons causing them to fire

Question 21

What do POMC neurons code for?

Answer 21

alpha-melanocyte stimulating hormone

Question 22

What does a-MSH bind to?

Answer 22

The MC4R receptor in the paraventricular nucleus

Question 23

What does activation of the MC4R receptor do?

Answer 23

It suppresses appetite

Question 24

What is the function of Agrp?

Answer 24

It acts as an endogenous antagonist to the MC4R receptor - blocks the receptor

Question 25

What can cause morbid obesity?

Answer 25

POMC deficiency and MC4-R mutations | Monogenic mutations

Question 26

What happens when you have a deficiency of leptin?

Answer 26

You become very hungry and put on a lot of body weight

Question 27

Where is leptin produced?

Answer 27

In white adipose tissues and circulates in plasma

Question 28

Where does leptin act on?

Answer 28

It acts on the hypothalamus regulating appetite (suppresses food intake) and thermogenesis (increasing energy expenditure)

Question 29

What are three aspects of the leptin regulatory loop that could lead to obesity?

Answer 29

Absent leptin Regulatory defect - not able to detect increases in adipose tissue and increase the amount of leptin in response Leptin resistance

Question 30

What the proportion of leptin to fat mass?

Answer 30

Leptin circulates in the plasma in concentrations that is proportional to fat mass

Question 31

Fat humans have...

Answer 31

high leptin

Question 32

Will injecting leptin solve obesity?

Answer 32

No. Obesity maybe due to a resistance to leptin. Leptin is present but doesn't signal effectively

Question 33

How can leptin be used to treat obesity?

Answer 33

Only small number of people who have a congenital leptin deficiency.

Question 34

What is the mutation related to congenital leptin deficiency?

Answer 34

mutation in the ob gene

Question 35

What are the symptoms of leptin deficiency?

Answer 35

Severely hyperphagic and obese

Question 36

Why do you feel less hungry after a meal?

Answer 36

Hormonal signalling from the gut

Question 37

How many amino acids make up Peptide YY?

Answer 37

36

Question 38

What is the function of PYY?

Answer 38

suppresses appetite

Question 39

When does PYY increase?

Answer 39

After a meal - roughly in proportion to the calories consumed

Question 40

What effects does PYY3-36 have on the arcuate nucleus?

Answer 40

Inhibits NPY release Stimulates POMC neurons Decreases appetite

Question 41

How is PYY3-36 formed?

Answer 41

When 2 amino acids from PYY is cleaved off

Question 42

How many amino acids is ghrelin made from?

Answer 42

28

Question 43

What is special about ghrelins structure?

Answer 43

It has a fatty acid group bound to the third amino acid serine

Question 44

When does ghrelin levels increase?

Answer 44

Before a meal and decreases after a meal

Question 45

What effects does ghrelin have on the arcuate nucleus?

Answer 45

Stimulates NPY/Agrp neurons Inhibits POMC neurons Increases appetite

Question 46

What comorbidities is obesity associated with?

Answer 46

Depression, stroke, mycoardial infarction, bowel cancer etc