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Year 2 Gastro > Appetite > Flashcards

Appetite Flashcards

(74 cards)

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1
Q

How many people die everywhere as a result of being overweight or obese?

A

2.8 million people

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2
Q

What are the three triggers for regulation of thirst?

A

Body fluid osmolality
Blood volume is reduced
Blood pressure is reduced

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3
Q

Which of the three thirst triggers is the most potent?

A

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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4
Q

How does ADH regulate osmolality?

A

Antidiuretic hormone (ADH) or vasopressin

Acts on the kidneys to regulate the volume & osmolality of urine
Collecting duct - Aquaporin 2 channel

When plasma ADH is low a large volume of urine is excreted (water diuresis)

When plasma ADH is high a small volume of urine is excreted (anti diuresis).

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5
Q

Where is ADH stored?

A

Posterior pituitary

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6
Q

What are the features of osmoreceptors?

A

Sensory receptors
Osmoregulation
Found in the hypothalamus

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7
Q

In which region of the hypothalamus are osmoreceptors found?

A

Organum vasculosum of the lamina terminalis (OVLT)

Subfornical Organ (SFO)

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8
Q

How do Osmoreceptors cause ADH release?

A

Cells shrink when plasma more concentrated

Proportion of cation channels increases – membrane depolarizes

Send signals to the ADH producing cells to increase ADH

Fluid retention
Invokes drinking

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9
Q

What is thirst decreased by?

A

Thirst is decreased by drinking even before sufficient water has been absorbed by the GI tract to correct plasma osmolality

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10
Q

What receptors are involved in thirst?

A

Receptors in mouth, pharynx, oesophagus are involved

Relief of thirst sensation via these receptors is short lived

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11
Q

When is thirst completely satisfied?

A

Thirst is only completely satisfied once plasma osmolality is decreased or blood volume or arterial pressure corrected.

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12
Q

How does changes is pressure regulate thirst?

A

Renin-angiotensin-aldosterone system

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13
Q

How does Aldosterone achieve water retention?

A

H2O retention via

Na+CL- absorption and K+ excretion

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14
Q

What does Angiontensin II do to increase water retention?

A

Vasoconstriction, increase sympathetic activity

ADH secretion

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15
Q

What occurs in a weight reduced - underfed state?

A 
Decreased sympathetic nervous activity 
Decreased energy expenditure
Increased hunger and food intake
Decreased thyroid activity
Weight gain
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16
Q

What occurs in a weight augmented - overfed state?

A

Increased sympathetic nervous activity
Increased energy expenditure
Decreased hunger and food intake
Weight loss

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17
Q

What is involved in appetite regulation?

A

Hypothalamus
Ghrelin
Leptin

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18
Q

What does hypothalamus do to regulate appetite?

A

Arcuate nucleus is an aggregation of neurons in the medial basal path

Produces appetite increasing (Orexigenic) and appetite decreasing (anorectic) peptides

Lateral hypothalamus - orexigenic

Ventrolmedial hypothalamus - associated with satiety

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19
Q

What do lesions in the ventromedial hypothalamus lead to?

A

Decreased satiety

Obesity

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20
Q

What are other hyporthalmic factors implicated in appetite regulation?

A

Endocannabinoids

AMP activated protein kinase

Protein thyrosine phosphatase

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21
Q

What are the main features of the arcuate nucleus?

A

Brain area involved in the regulation of food intake

Incomplete blood brain barrier, allows access to peripheral hormones.

Integrates peripheral and central feeding signals

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22
Q

What are the two neuronal populations in the arcuate nucleus?

A

Two neuronal populations:

Stimulatory (NPY/Agrp neuron)
Inhibitory (POMC neuron)

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23
Q

What can the arcuate nucleus neurons be affected by?

A

Leptin

Insulin

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24
Q

What do POMC neuron activation do?

A

Decreases feeding

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25
What do NPY/Agrp neurone activation do?
Increases feeding
26
How does the melanocortin system work?
Melanocortins are products of the POMC gene Regulates energy balance in feeding behviours and energy expenditures MC4R receptors are stimulated by serotonin Leads to reduction in appetitis
27
What does POMC deficiency and MC4-R mutations cause?
Obesity
28
What higher brain regions also play a role in appetite?
Higher centres. Amygdala- emotion, memory. Other parts of the hypothalamus, e.g. lateral hypothalamus Vagus to brain stem to hypothalamus.
29
What is the adipostat mechanism?
Circulating hormone produced by fat More fat, more hormones Hypothalamus senses the concentration of hormone. Hypothalamus then alters neuropeptides to increase or decrease food intake. Perhaps a problem with the regulation of the adipostat mechanism leads to obesity ?
30
What is the ob/ob mouse?
Obese mouse Unable to produce leptin leading to obesity Identification of the gene in the mouse led to discovery of leptin significance
31
What are the features of leptin?
Meaning - thin Discovered in 1994. Missing in the ob/ob mouse. Made by adipocytes in white adipose tissue. Circulates in plasma. Acts upon the hypothalamus regulating appetite (intake) and thermogenesis (expenditure). Plays a role in atherosclerosis
32
What is congenital leptin deficiency?
Very rare Causes severe obesity early in life Constant hunger
33
What is the systemic effects of leptin?
Low when low body fat High when high body fat Replacement in the ob/ob mouse decreases weight Hormone that decreases food intake and increases thermogenesis
34
What are the three mechanisms of action of leptin?
Insufficient production Defective receptor signalling Decreased sensitivity of leptin
35
What are the features of leptin resistance?
Leptin circulates in plasma in concentrations proportional to fat mass Fat humans have high leptin Obesity due to leptin resistance- hormone is present but doesn’t signal effectively Leptin is ineffective as a weight control drug.
36
Why do we feel less hungry after a meal?
Hormonal signals from gastrointestinal hormones
37
What secretes the gastrointestinal hormones?
Enteroendocrine cells of stomach
38
What are the two main gastrointestinal hormones?
Ghrelin Stimulates appetite, increases gastric emptying Peptid YY Inhibits food intake
39
When are the blood levels of ghrelin highest?
Blood levels of ghrelin are highest before meals | help prepare for food intake by increasing gastric motility and acid secretion
40
What does ghrelin do?
Directly modulates neurons in the arcuate nucleus Stimulates NPY/Agrp neurons. Inhibits POMC neurons
41
What are the affects of ghrelin?
Increases appetite Regulation of reward, taste sensation, memory, circadian rhythm
42
What is PPY?
Short peptide released in the terminal ileum (TI) and colon in response to feeding (36 Amino acids)
43
What are the affects of PPY?
Reduces appetite – can be digested or injected IV Food arriving to the TI and colon results in PYY release Inhibits NPY release Stimulates POMC neurons
44
What is the affect of PPY when taken?
Experience less hunger Early fullness Nausea
45
What are co-morbidities associated with obesity?
``` Depression Stroke MI Hypertension Diabetes Peripheral vascular disease Gout Osteoarthritis Bowel cancer Sleep apnoea ```
46
What is adipisia?
Inappropriate lack of thirst | with consequent failure in order to correct hyperosmolarity
47
What are the types of polydipsia?
Primary | Secondary
48
What are the main features of secondary polydipsia?
More common Medical issues that disrupt any step in osmoregulation or alter ADH can cause secondary polydipsia
49
What are the causes of secondary polydipsia?
Chronic medical conditions Medications Dehydration
50
What chronic medical conditions cause secondary polydipsia?
``` Diabetes insipidus & mellitus  Kidney failure Conn’s syndrome (primary aldosteronism) Addison's disease (hypoadrenocorticsm) Sickle cell anaemia ```
51
What medications cause secondary polydipsia?
Diuretics Laxatives Both result in dehydration Antidepressants
52
What causes dehydration?
``` Acute illness Sweating Fevers Vomiting Diarrhoea Underhydration ```
53
What does insipid mean?
Tasteless
54
What does Mellitus mean?
Sweet tasting
55
What are the main features of diabetes mellitus?
General population - common Related to high blood sugar Treatment of high blood sugar  
56
What are the main features of diabetes insipidus?
General population - uncommon Related to pituitary problems Impaired ADH production Treatment with desmopressin
57
What causes primary polydipsia?
``` Mental illness - psychogenic polydipsia (or acquired) Schizophrenia  Mood disorders - depression and anxiety Anorexia Drug use ``` Brain injuries Organic brain damage
58
Why is polydipsia a problem?
``` Kidney and bone damage Headache Nausea Cramps Slow reflexes Slurred speech Low energy Confusion Seizures ```
59
What are the 4 types of polydipsia?
Type A Type B Type C Type D
60
Give examples of eating disorders
``` Binge eating disorder Anorexia nervosa Bulimia nervosa Pica Rumination syndrome Avoidant/restrictive food intake disorder  ```
61
Describe global prevalence of eating disorders
Global eating disorder prevalence ↑ed from 3.4% to 7.8% between 2000 and 2018. 70 million people live with eating disorder
62
What is Pica?
Eating inappropriate things | e.g. hair, soil, dust
63
What is rumination syndrome?
Regurgitate and swallow | repeat
64
What are the signs of anorexia?
Low BMI, continuous weight loss, amenorrhea, halitosis, mood swings, dry hair, skin & hair thinn
65
What are the different BMI categories for anorexia?
Mild: BMI > 17 Moderate: BMI of 16–16.99 Severe: BMI of 15–15.99 Extreme: BMI < 15
66
What are the causes of anorexia?
Genetic, environmental, psychological, sociological
67
What is halitosis?
Bad breath
68
What is the mechanism of anorexia?
Via serotonin release | Increase in CSF
69
What percentage of the worlds population will be obese by 2030?
51%
70
Why is obesity increasing?
Cheap, calorie rich, readily available food
71
What are the screening tools used for obesity?
Height, weight and abdominal girth Medical history: Dietary and physical activity patterns, psychosocial factors, weight-gaining medications, familial traits BMI = kg/m2 BMI of ≥30 or ≥25 + comorbidity or risk factor
72
What surgical treatments are available for obesity?
People with a > BMI 40 or 35+ comorbidities Various procedures Most common Roux-en-Y gastric bypass & sleeve gastrectomy WL 5 yrs after BS: 30% - 35% Remission of comorbidities Diabetes (80%) OSA (80%-85%)
73
What are the hormones related to obesity?
GLP1 and GLP2: Stimulate insulin release Inhibit glucagon release Ghrelin: Hunger hormone NPY activation – initiate appetite PYY: Satiety anorexogenic
74
What hormonal changes are seen after bariatric surgery?
Ghrelin reduces GLP1, GLP2 and PYY elevated

Year 2 Gastro (10 decks)

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