Alimentary System 12 - Appetite Regulation Flashcards Preview

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Flashcards in Alimentary System 12 - Appetite Regulation Deck (20)
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1
Q

When does an individual percieve thirst?

A
  • When blood fluid osmolarity is increased (most potent)
  • When blood volume is reduced
  • When blood pressure is reduced
2
Q

Compare the change in plasma osmolarity required to cause a strong desire to drink to the change in blood volume or arterial pressure required

A
  • Plasma osmolarity requires change of 2-3%

- Blood volume or arterial pressure need to decrease by 10-15%

3
Q

Where are osmoreceptors found?

A

In the hypothalamus, organum vasculosum laminae terminalis and the subfornical organ

4
Q

How do osmoreceptors respond to changes in osmolarity?

A
  • Shrink or swell in response to plasma changes

- Stimulate alteration of ADH release and regulate thirst

5
Q

How does thirst cessation occur?

A
  • Thirst is decreased by drinking even before the water has been absorbed to correct plasma osmolarity
  • Receptors in the mouth, pharynx and oesophagus are involved
  • Relief of thirst via these receptors is short lived, thirst is satisfied once plasma osmolarity is decreased or blood volume or arterial pressure corrected
6
Q

List the hormones involved in body weight homeostasis

A
  • Ghrelin, PYY and other gut hormones
  • Leptin
  • Neural input
7
Q

List the functions of the arcuate nucleus, and describe how its structure allows it to perform its function

A
  • Involved in regulation of food intake
  • Incomplete blood brain barrier to access peripheral hormones
  • Contains stimulatory (NPY/Agrp) and inhibitory (POMC) neurones
  • Communicate with the whole brain and paraventricular nucleus
8
Q

Describe how POMC regulates food intake

A
  • POMC is converted to a-MSH which has a postitive effect on melanocortin 4 receptor in the hypothalamus.
  • Stimulated to suppress food intake
9
Q

Describe how Agrp regulates food intake in humans

A

Agrp acts as an antagonist of the melanocortin 4 receptor, which makes you feel hungry

10
Q

List the human CNS mutations affecting appetite

A
  • No NPY or Agrp mutations discovered in himans

- POMC deficiency and MC4-R mutations cause morbid obesity

11
Q

What other brain regions, than the arcuate nucleus affect hunger?

A
  • Higher centres
  • Amygdala (emotion and memory)
  • Other parts of the hypothalamus like the lateral hypothalamus
  • Vagus nerve to brain stem to hypothalamus
12
Q

Describe the process of the adipostatic mechanism

A
  • Circulating hormone produced by fat, such as leptin made in white adipose tissue
  • Hypothalamus senses the concentration of hormone
  • Hypothalamus alters neuropeptides to increase or decrease food intake
13
Q

What was missing in the ob/ob mouse?

A

Leptin, therefore he felt like he was starving and kept eating

14
Q

List the functions of leptin

A
  • Low when low body fat
  • High when high body fat
  • Replacement when there is a mutation decreases weight
  • Hormone that decreases food intake and increases thermogenesis
  • Long term regulator
15
Q

How does the leptin regulatory loop lead to obesity in most people?

A
  • They become desensitised to high levels of leptin, or already have leptin resistance - which came first?
  • Some cases of leptin deficiency
16
Q

List the short term regulators of appetite

A
  • Ghrelin

- Peptide YY

17
Q

List the functions of peptide YY

A
  • Inhibit NPY release
  • Stimulates POMC neurons
  • Decreases appetite
18
Q

List the functions of ghrelin

A
  • Stimulates NPY/Agrp neurons
  • Inhibits POMC neurons
  • Increases appetite
19
Q

What is the future of obesity teatment?

A
  • Gut hormones could be a novel treatment
  • Target relevent circuits
  • Released daily without side effects
  • Exert effect throughout life without escape
20
Q

If genetics havent changed over the past decade, why is obesity increasing?

A

As our body hormones determine our weight in the environment we are in, and in an environment where we have access to unhealthy food and public transport