Appetite regulation

Question 1

When does a person perceive thirst?

Answer 1

When

• body fluid osmolality increases
• blood volume decreased
• blood pressure reduced

a 2-3% change in plasma gives big stimulus
- same as 10pc loss of blood

Question 2

What are the effects of ADH?

Answer 2

Regulate volume and osmolality of urine

- high ADH means conc urine and vv

Question 3

How is ADH release potentiated?

Answer 3

Osmoreceptors in the

• hypothalamus
• OVLT - organum vasculosum
• SFO - subfornical organ

Question 4

How do osmoreceptors see change?

Answer 4

Osmolality changes

Cells shrink or swell in response
- send signals to ADH producing cells in the hypothalmus for ADH release

Question 5

How is thirst quenches?

Answer 5

On the intake of water
- short lived

Then satisfied when plasma osmolality corrected

Question 6

How does RAAS affect thirst?

Answer 6

AGII production causes VC but also stimulates thirst

• needs to retain water

Question 7

Specifically, how does AGII stimulate thirst?

Answer 7

Thirst sensation

SFO neuron activation

Question 8

how is body weight balanced? where is it regulated? how?

Answer 8

Food intake and energy expenditure

regulated in the hypothalamus

• integrates inputs from nervous system
• leptin and ghrelin

Question 9

What is the importance of the arcuate nucleus?

Answer 9

Incomplete blood-brain barrier, allows access to peripheral hormones
- integrates peripheral and central feeding signals

Can produce signals

• STIMULATORY
  
  • NPY / Agrp
• INHIBITORY
  
  • POMC

Question 10

How do NPY or POMC cause increase or decrease feeding?

Answer 10

AP goes to paraventricular nucleus which will have downstream effects to increase or decrease food

Question 11

Which receptor do Agrp and POMC work on?

Answer 11

MC4R - melanocortinin 4 receptor

BUT - POMC has to be chopped to alpha MSH

Question 12

What might POMC deficiency and MC4-R mutation lead to?

Answer 12

Morbid obesity

Question 13

Where else may signals for appetite arise from?

Answer 13

Higher centres

Amygdala

Vagus

Question 14

What is the adipostat mechanism?

Answer 14

Hormone produced by fat

Hypothalamus senses the concentration of this hormone, altering neuropeptides to increase or decrease food intake

Problem leads to obesity

Question 15

Which hormone is less in obese people? Where should it be made?

Answer 15

LEPTIN

• by white adipocytes
• acts in order to regulate appetite - suppresses intake, increases expenditure

Question 16

What kinds of defects in leptin could lead to obesity?

Answer 16

Absence of leptin

Regulatory defect

Leptin resistance

Question 17

People who are obese tend to have leptin resistance, absence or defects?

Answer 17

Resistance

- obese people have high leptin

Question 18

In terms of appetite regulation, are leptin and ghrelin long or short term signals of homeostasis?

Answer 18

Leptin - long

Ghrelin - short

Question 19

Why does hunger diminish after a meal?

Answer 19

Hormonal signal

• Ghrelin
• PYY

Question 20

When is PYY secreted?

Answer 20

Much higher on higher calories

Question 21

How does PYY decrease appetite?

Answer 21

Inhibits NPY release and stimulates POMC from the arcuate nucleus

Question 22

What happens to ghrelin upon eating?

Answer 22

It drops

Opposite effect to PYY

Question 23

How does ghrelin stimualte hunger

Answer 23

Stimulate NPY, Agrp neurons

Inhibts POMC