Intestinal hormones and motility Flashcards

1
Q

What is the main regulatory organ for appatite?

A

ventromedial nucleus of the hypothalamus

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2
Q

What are the different theories of appetite regulation?

A

Lipostat - fat deposits and leptin
Gut peptides - CCK
Glucostat - glucose/VFAs/AAs
Thermostat

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3
Q

Describe the lipostat hypothesis of appetite regulation

A

Adipose tissue produces leptin proportionally to amount of fat -> hypothalamus -> decreases food intake and increase energy output

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4
Q

Describe the gut peptide hypothesis of appetite regulation

A

GI hormones e.g., glucagon released in response to food and act on hypothalamus to inhibit food intake
CCK found in brain and is released upon expansion of the stomach
Ghrelin from stomach increases before meals and stimulates appetite at hypothalamus levels by reducing leptin levels

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5
Q

Describe the glucostat hypothesis of appetite regulation

A

High glucose e.g., after meal -> stimulates satiety (fullness) centre in hypothalamus

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6
Q

Describe the thermostat hypothesis of appetite regulation

A

Low body temp stimulated appetite and opposite for high temp

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7
Q

Label the oesophagus

A
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8
Q

Describe the process of deglutition/swallowing

A

Deglutition/swallowing:
Oral phase:
Bolus formed and voluntarily moved to pharynx (tongue thckens to push bolus)
Pharyngeal phase:
Pharynx is activated to propel food to oesophagus
Oesophageal phase:
Bolus moves to oesophagus via peristalsis -> stomach

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9
Q

Describe the secretory role of the stomach

A

Exocrine:
- mucin producing cells (cardia, fundus, corpus)
- parietal cells - HCL (fundus and corpus)
- chief cells - pepsinogen + lipase (fundus and corpus)

Endocrine:
- histamine producing/ECL cells (pylorus)
- gastrin producing cells/G cells (fundus and corpus)

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10
Q

Describe the neural stimulation of the stomach

A

Long reflex
Stomach expansion and peptides stimulates secretion via acetylcholine (CNS)

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11
Q

Describe the hormonal stimulation of the stomach

A

short reflex
stomach expansion and peptides => gastrin release + impulse to CNS

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12
Q

what is the for mechanism for stomach emptying?

A

Cajal cells between circular and longitudinal muscle layers stimualte contraction via gap junction to empty stomach
related to mesenteric nerve plexus

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13
Q

How is stomach evacuation stimulated?

A

Decreased gastric pH
wall distension => influx to submucosal plexus => parasympathetic nerve influx to stomach effectors e.g., smooth muscle, parietal cells => evacuation

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14
Q

What inhibits stomach emptying?

A

Stomach emptying is inhibited by duodenal factors, secretin, GIP and CKK

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15
Q

What happens when chyme enters duodenum

A

Chyme enters low pH environment in duodenum which, along with FAs and peptides triggers CKK and secretin release which increase pancreatic juice and bile flow into duodenum and also slows stomach emptying

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16
Q

How is peristalsis managed in the SI?

A

Small intestinal peristalsis and segmentation managed by mesenteric plexus and CNS

17
Q

What stimulates large intestine contraction?

A

Stomach and duodenum promote large intestine contraction via mesenteric NS (gastro-colic reflex)

18
Q

What are the 4 types of contraction involved in movement of ingesta?

A

segmentation
peristalsis
antiperistalsis
mass movement

19
Q

What drives mass movement in the intestines?

A

stretch of wall/mechanosensor

20
Q

Describe the induction of vomiting/emesis

A

Chemoreceptor zone of the emetic centre lies outside BBB so can be stimulated by toxins in the blood

GI inputs to the emetic centre:
- Cranial nerve X (Vagus) - activated when pharynx is irritated
- Vagal and enteric NS inputs transmit info about GIT, irritation of the GI mucosa activates receptors of these inputs