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Gastro > Appetite > Flashcards

Appetite Flashcards

1
Q

What are the three stimuli that induce thirst?

A

Blood plasma osmolality increased
Blood volume reduced
Blood pressure reduced

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2
Q

Osmolality vs Osmolarity

A

Osmolarity refers to the number of solute particles per 1 L of solvent, whereas osmolality is the number of solute particles in 1 kg of solvent

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3
Q

Which of these is the most potent stimulus?

A

Blood plasma osmolality

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4
Q

What hormone is responsible for the homeostasis of blood osmolality and how does it do this?

A

ADH/Vasopressin - migrates to collecting duct and stimulates integration of aquaporin 2 receptors on apical side of collecting duct

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5
Q

ADH and urine output

A

High ADH = low urine output
Low ADH = high urine output

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6
Q

What are osmoreceptors

A

Sensory receptors that control osmoregulation.
Found in the hypothalamus
sensitive to blood osmolality

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7
Q

Which specific region of the hypothalamus are osmoreceptors found?

A

Subfornical Organ (SFO)
Organum Vasculosum of Lamina Terminalis (OVLT)

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8
Q

Describe the mechanism of ADH release at the site of osmoreceptors

A

Cells become hypotonic and shrink
Proportion of cation channels increases due to less SA
Positive charge influx results in ADH production
Fluid retention via drinking

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9
Q

When is thirst truly satisfied?

A

Plasma osmolality decreased or blood volume increased

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10
Q

Why is sensation of thirst important?

A

Time rq for water to reach the GI tract and plasma osmolality to be corrected.
Sensation provides short term relief and prevents excessive fluid intake - affect salt balance

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11
Q

Describe the renin angiotensin system

A

Low BP -> renin release from juxtaglomerular cells, converts angiotensinogen into angiotensin I in the liver, which is converted to angiotensin II by ACE.

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12
Q

What are the 4 effects of angiotensin II?

A

Thirst,
ADH secretion,
Vasoconstriction (sympathetic activation),
Aldosterone (using Na/K pump for H2O retention), Nacl absorption and k+ excretion

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13
Q

The impact of the change in fat mass

A

Increase in fat mass causes
- increased sympathetic activity
- increased thyroid function
- decreased appetite

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14
Q

What are the two nuclei in the hypothalamus involved in appetite control?

A

Arcuate Nucleus,
Paraventricular Nucleus

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15
Q

What is the function of the arcuate nucleus?

A

aggregation of neurons in the mediobasal hypothalamus
Store of neural peptides (NPY/AGRP , POMC)

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16
Q

Orexigenic peptides

A

Appetite stimulant neural peptides

17
Q

Anorectic peptides

A

Appetite suppressive neural peptides

18
Q

What is the function of the paraventricular nucleus?

A

Controls appetite and energy expenditure
Neurons project to posterior pituitary secreting vasopressin and oxytocin

19
Q

Function of the lateral hypothalamus

A

Produces orexigenic peptides (stimulant)
L - Loves food

20
Q

Function of the ventromedial hypothalamus

A

Associated with hunger
V - aVoids food

21
Q

What structural property of the arcuate nucleus allows it to be able to respond to the peripheral environment?

A

Incomplete blood brain barrier, access for peripheral hormones

22
Q

Neurons in the stimulatory pathway of ARC nucleus
- appetite stimulus

A

Neuropeptide Y (NPY),
Agouti-related Peptide (AGRP) - inhibits POMC

23
Q

Neurons in the inhibitory pathway of the ARC nucleus
- appetite suppression

A

Pro-opio melanocortic hormone (POMC)

24
Q

Describe the hunger inhibitory pathway release of neural peptides on MC4R?

A

POMC is released from ARC, then converted to alpha-MSH, moves through third ventricle into paraventricular nucleus, binding to MC4R

25
Q

Mutations in neurons affecting appetite

A

NPY/AGRP have no effect on appetite
POMC deficiency and MC4R issues

26
Q

Function of adipostat

A

Circulating hormone produced by fat
Hypothalamus adjusts release of neuropeptides depending on the concentration

27
Q

Function of leptin

A

Made in adipose tissue and enterocytes
Decreased food intake via appetite suppression, increased thermogenesis

usually high in those with greater weight

28
Q

Congenital leptin deficiency

A

EXcessive weight gain due to overwhelming drive to eat

29
Q

Why is leptin ineffective as a weight control drug

A

Normal leptin levels correspond to weight
Overweight/obese individuals develop resistance

30
Q

What is the primary reason appetite is controlled after food consumption?

A

Release of gut hormones

31
Q

Cells secreting gut hormones

A

Enteroendocrine cells in stomach, pancreas and small bowel

32
Q

What gut hormones are mainly responsible for controlling appetite?

A

Ghrelin
PYY

33
Q

What are the functions of ghrelin?

A

stimulates appetite, increases gastric emptying, motility and acid secretion

34
Q

What is the mechanism of action of ghrelin?

A

Stimulates NPY/ARGP and inhibits POMC in the arcuate nucleus

35
Q

What is the function of Peptide YY?
And where does it act

A

Decreases appetite: Inhibits food intake
acts at the terminal ileum

36
Q

What is the mechanism of action of Peptide YY?

A

Stimulates POMC in ARC, inhibits NPY

37
Q

Major CNS region regulating hunger and thirst

A

Hypothalamus

Gastro (10 decks)

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