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LSS 2 - Abdomen, Alimentary and Urinary systems > AS Lecture 15 - Appetite Regulation > Flashcards

AS Lecture 15 - Appetite Regulation Flashcards

1
Q

What does appetite regulation entail?

A

Control of thirst Hypothalamic circuits controlling body weight Peripheral signals of body homeostasis - long term: leptin, short term: ghrelin, PYY

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2
Q

When does someone perceive thirst?

A

Body fluid osmolality is increased Blood volume is reduced Blood pressure is reduced Most potent is change of 2-3% of osmolality BUT 10-15% decrease is needed for same response from blood vol/arterial pressure

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3
Q

What does ADH/VP do?

A

Acts on kidneys to regulate volume and osmolarity of urine - when plasma ADH is low water diuresis occurs; when plasma ADH is high, antidiuresis occurs (small vol of urine)

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4
Q

Where are osmoreceptors found?

A

In the hypothalamus, organum vasculosum of the lamina terminalis, subfornical organ

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5
Q

What do the osmoreceptors do?

A

Sense changes in body fluid osmolality -> cells shrink/swell in response, sending signals to the ADH producing cells in the hypothalamus to alter ADH release

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6
Q

How is water balance maintained when there is increased plasma osmolality?

A

Invokes drinking and ADH release Increases ADH stimulating kidneys to conserve water

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7
Q

How is water balance maintained when there is decreased plasma osmolality?

A

Thirst is suppressed and ADH release is decreased Absence of aDH makes kidney excrete more water

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8
Q

How is thirst decreased and when is it decreased?

A

It can be decreased by drinking even before water has been absorbed by GIT to correct plasma levels. They relieve the sensation for a short time

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9
Q

When is thirst completely satisfied?

A

Once plasma osmolality is decreased or blood volume/arterial pressure is corrected

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10
Q

How is the renin-angiotensin-aldosterone system involved in the regulation of thirst?

A

AngII evokes sensation of thirst, increased when blood vol and pressure are reduced -> SFO neurons activated, contributing to the homeostatic response to restore/maintain body fluids at their normal level

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11
Q

How is body weight homeostasis maintained?

A

Ghrelin, PYY and other gut hormones, neural input from periphery and other brain regions and leptin are detected by the hypothalamus and then react to food intake and energy expenditure

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12
Q

What is the pathways with which skeletal muscle, pancreas, stomach, white adipose tissue and gut relay signals to higher centres?

A
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13
Q

What is the structure of the hypothalamus? FITB

A
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14
Q

What is the arcuate nucleus?

A

Key brain area involved in the regulation of food intake -> it has an incomplete blood brain barrier, allowing access to peripheral hormones Integrates peripheral and central feeding signals 2 neuronal populations: Stimulatory and inhibitory which are distinct from each other and regulated independently

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15
Q

Which is the stimulatory neuron in the arcuate nucleus?

A

NPY/Agrp neuron

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16
Q

Which is the inhibitory neuron in the arcuate nucleus?

A

POMC neuron

17
Q

How is appetite and energy expenditure controlled?

A

Cells bodies are in arcuate nucleus and axons extend to para ventricular nucleus

18
Q

What is the melanocortin system?

A

Argp blocks signal from alpha MSH which causes hunger

19
Q

Give 3 examples of types of human CNS mutations that affect appetite

A

No NPY/Agrp mutations associated with appetite discovered in humans POMC deficiency and MC4-R mutations can cause morbid obesity

20
Q

What signals from other brain regions can affect appetite?

A

From higher centres Amygdala affects emotion and memory Other parts of the hypothalamus -> lateral hypothalamus Vagus to brainstem to hypothalamus

21
Q

What is the adipostat mechanism?

A

Concentration of circulating hormone produced by fat is detected by hypothalamus which then alters neuropeptides to increase/decrease food intake

22
Q

What is leptin?

A

Made by adipocytes in white adipose tissue, circulates in plasma and acts upon the hypothalamus regulating appetite and thermogenesis 167 a.a. hormone

23
Q

How is the concentration of leptin different in different people?

A

Low when low body fat and high when high body fat

24
Q

What does leptin do?

A

Decreases food intake and increases thermogenesis

25
Q

What are the 3 possible ways the leptin regulatory loop can lead to obesity?

A
26
Q

What is leptin resistance mechanism?

A

Leptin circulates in plasma in concentrations proportional to fat mass, so obesity due to leptin-resistance

27
Q

What is congenital leptin deficiency?

A

Small number of cases identified -> mutation in ob gene, so person becomes severly hyperphagic and obese

28
Q

How is congenital leptin deficiency treated?

A

Leptin replacement - which is effective in reducing body weight

29
Q

What are the different enzymes secreted from the gut and their functions? FITB

A
30
Q

What is the function of PYY?

A

Directly modulates neurons in the arcuate nucleus -> inhibits NPY release, stimulates POMC neurons and decreases appetite. Rises directly with amount of calories ingested

31
Q

What is the function of ghrelin?

A

Directly modulates neurons in the arcuate nucleus -> stimulates NPY/Agrp neurons, inhibits POMC and increases appetite

32
Q

What is the future of obesity treatment?

A

Gut hormones may represent a novel treatment for obesity, as it targets only relevant circuit, it’s released daily without ‘side effects’ and exerts effect throughout life without escape

33
Q

How is the brainstem triggered from the release of ghrelin and PYY? FITB

A
34
Q

What comorbidities is obesity associated with?

A

Depression, stroke, sleep apnoea, myocardial infarction, hypertension, diabetes, bowel cancer, osteoarthritis, peripheral vascular disease, gout

35
Q

What is the thrifty gene hypothesis?

A

In the past it was more sensible to be able to put on weight as the thin wouldn’t survive famines, so obesity genes selected for

36
Q

What are circumventricular organs?

A

They have an incomplete blood-brain barrier, so can sense changes in blood and respond to the changes. E.g. Organ vasculosum, subfornical organ

37
Q

What receptors are involved in thirst detection?

A

Receptors in mouth, pharynx, oesophagus

38
Q

What type of hormone is ghrelin?

A

Protein hormone with fatty acid chain (thought to help with passing the blood brain barrier)

39
Q

What type of hormone is PYY?

A

Protein hormone

LSS 2 - Abdomen, Alimentary and Urinary systems (29 decks)

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