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Phase 1b - Gastroenterology > Appetite > Flashcards

Appetite Flashcards

1
Q

What 3 factors stimulate thrist?

A
  • Body fluid osmolality is increased
  • Blood volume is reduced
  • Blood pressure is reduced

  • 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
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2
Q

How is thirst decreased?

A

Drinking

Receptors in mouth, pharynx, oesophagus are involved

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3
Q

Thirst is decreased by drinking even before sufficient water has been absorbed by the GI tract to correct plasma osmolality and relief of thirst sensation via these receptors (in mouth, pharynx and oesophagus) is short lived. When is thirst completely satisfied?

A
  • Once plasma osmolality is decreased or blood volume or arterial pressure corrected
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4
Q

What happens when there is an increase in osmolarity (6 steps)?

A
  1. Osmoreceptor cells shrink when plasma is more concentrated
  2. Proportion of cation channels increase - membrane depolarises
  3. Send signal to the ADH producing cells to increase ADH
  4. Antidiuretic hormone (ADH) / Arginine vasopressin (AVP) / Vasopressin acts on the kidneys to regulate the volume & osmolarity of urine
  5. Increase in ADH causes a decrease in urine and an increase in urine osmolarity
  6. Fluid retention causes drinking
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5
Q

What are osmoreceptors?

A

Sensory receptors

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6
Q

Where are osmoreceptors found withing the hypothalamus (2)?

A
  • Organ vasculosum of the lamina terminalis (OVLT)
  • Subformical organ (SFO)
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7
Q

Where does ADH act?

A
  • Aquaporin 2 channel in the collecting duct
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8
Q

What happens when there is a decrease in blood pressure (6 steps)?

A
  1. Decrease in BP causes the juxtaglomerular cells of renal afferent arteriole to release renin
  2. Renin is converted to Angiotensin I (ca. Angiotensinogen) in the liver
  3. Renin is Angiotensin I to Angiotensin II (ca. ACE) in the lungs
  4. Angiotensin II causes: Thirst / Vasoconstriction, increase sympathetic activity / ADH secretion
  5. Angiotensin II causes the zona glomerulosa of adrenal cortex to release aldosterone
  6. Aldosterone causes H2O retention via Na+CL- absorption and K+ excretion
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9
Q

What happens when there is a reduction in fat mass (4)?

A
  • Increased in food intake / hunger
  • Decreased energy expenditure
  • Decreased thyroid function
  • Decreased SNS activity

To encourage weight regain

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10
Q

What happens when there is an increase in adipose tissue (3)?

A
  • Decreased in food intake / hunger
  • Increased energy expenditure
  • Increased SNS activity

To encourage weight loss

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11
Q

What factors influence food intake & energy expenditure (4)?

A
  • Gherlin, PYY & other gut hormones
  • Neural input from the periphery and other brain regions
  • Leptin
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12
Q

Define orexigenic.

A

Appetite stimulant

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13
Q

Define anorectic.

A

Appetite suppressive

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14
Q

Name this structure in the hypothalamus.

A

Lateral hypothalamus

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15
Q

What is produced by the lateral hypothalamus?

A

Orexigenic peptides

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16
Q

Name this structure in the hypothalamus.

A

Ventromedial hypothalamus

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17
Q

What is the ventromedial hypothalamus associated with?

A

Feelings of Satiety and Hunger

18
Q

Name this structure in the hypothalamus.

A

3rd Ventricle

19
Q

Name this structure in the hypothalamus.

A

Paraventricular nucleus

20
Q

What is the function of the paraventricular nucleus?

A
  • Contains nurones that project to the posterior pituitary to stimulate the release of ADH & oxytocin
21
Q

Name this structure in the hypothalamus.

A

Arcuate nucleus

22
Q

What is the arcuate nucleus?

A
  • An aggregation of neuorones in the medial basal part
  • Produces both orexigenic and anorexic factors
23
Q

What are the orexigenic factors released by the arcuate nucleus (2)?

A
  • Neuropeptide Y (NPY)
  • Agouti-related peptide (AgRP)
24
Q

What are the anorexic factors released by the arcuate nucleus (2)?

A
  • Proopiomelanocortin (POMC)
  • Cocaine- and amphetamine-regulated transcript (CART)
25
Q

What regions of the brain (outside the hypothalamus) influence food intake and energy expenditure (2)?

A
  • Amygdala - emotion, memory
  • Vagus nerve to brain stem to hypothalamus
26
Q

What peripheral factors influence food intake and energy expenditure (5)?

A
  • Leptin
  • Adipostat
  • Ghrelin
  • Peptide YY (PYY)
  • GLP1 & GLP2
27
Q

Where is leptin produced?

A
  • Made by adipocytes in white adipose tissue and enterocytes

Leptin concentration is positively correalated with body fat

28
Q

Where is leptin found?

A

Circulates in plasma

29
Q

What is the effect of increased leptin?

A
  1. Increased leptin
  2. Decreased NPY / AgPR in the arcuate nucleus
  3. Decreased AgPR in arcuate nucleus
  4. Decreased food intake / Increased energy expenditure through the Melanocortin 4 Receptor (MC4R)

AND

  1. Increased leptin
  2. Decreased Melanin-concentrating hormone (MCH) / Orexins in the lateral hypothalamus
  3. Decreased food intake / Increased energy expenditure through the Melanocortin 4 Receptor (MC4R)
30
Q

What is leptin resistance?

A
  • POMC deficiency & MC4R mutations cause morbid obesity

No NPY / AgPR mutations associated with appetite disorders in humans

31
Q

Where is adipostat produced?

A

Adipose tissue

32
Q

Where is adipostat found?

A

Circulating in the blood

33
Q

What is the function of adipostat?

A

Acts like a (complicated) thermostat:
* Hypothalamus senses the concentration of hormone
* Hypothalamus alters neuropeptides to increase or decrease food intake

34
Q

What does ghrelin regulate (4)?

Gherlin is a gastrointestinal hormone
Gastrointestinal hormone: Secreted byenteroendocrine cellsin thestomach, pancreas & SB

A
  • Regulation of reward, taste sensation, memory & circadian rhythm
35
Q

What is the function of gherlin?

Gherlin is a gastrointestinal hormone
* Gastrointestinal hormone: Secreted byenteroendocrine cellsin thestomach, pancreas & SB

A
  • Stimulates NPY / AgPR neurones
  • Inhibits POMC / CART neurones

Increase appetite

36
Q

When are gherlin levels the highest?

A
  • Before meals: help prepare for food intake by increasing gastric motility and acid secretion
37
Q

Where is peptide YY (PYY) released and in what response?

A
  • Short pepdite released in the terminal ileum (TI) & colon in response to feeding
38
Q

What is the function of peptide YY (PYY) (4 steps)?

A
  1. Food at terminal ileum & colon
  2. PYY released
  3. Inhibits NPY release & stimulate POMC neurones
  4. Decrease appetite
39
Q

What is the function of GLP1 & GLP2 (2)?

A
  • Stimulate insulin release
  • Inhibit glucagon release
40
Q

What comorbidities are associated with obesity (10)?

A
  • Depression
  • Sleep apnoea
  • Bowel cancer
  • Osteoarthritis
  • Gout
  • Stroke
  • Myocardial Infarction
  • Hypertension
  • Diabetes
  • Peripheral vascular disease

Phase 1b - Gastroenterology (13 decks)

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