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Physiology 1 > Introduction To The Funcions And Control Of The Alimentary Tract > Flashcards

Introduction To The Funcions And Control Of The Alimentary Tract Flashcards

1
Q

What inhibits smooth muscle tone mechanoreceptors?

A

Vagal reflex (Vasoactive intestinal peptide and nitric oxide)

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2
Q

What does the antral region of the stomach body do?

A

Mixes/grinds food with gastric secretions

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3
Q

How much gastric juice does the stomach store in 24 hours?

A

2-3 litres

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4
Q

What is included in gastric juice?

A

Mucus, Pepsinogen, intrinsic factor and lipase

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5
Q

What does gastric juice help with?

A

Digestion and absorption of food

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6
Q

What is the function of mucus in the stomach?

A

Lubricant that protects stomach and colon from gastric acid

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7
Q

What does lipase do?

A

TGs -> fatty acids and glycerol

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8
Q

What is mucus secreted by?

A

Goblet cells and mucus neck cells

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9
Q

What is pepsin secreted by?

A

Chief cells or peptic cells as pepsinogen

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10
Q

What is pepsinogen?

A

Inactive enzyme that forms pepsin in an acidic environment

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11
Q

What is pepsins function?

A

Protein digestion

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12
Q

What is HCLs function?

A

Important in defence and conversion of pepsinogen -> pepsin

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13
Q

What is HCL secreted by?

A

Parietal cells

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14
Q

What are intrinsic factors secreted by?

A

Parietal cells

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15
Q

What is intrinsics function?

A

Vit B12 absorption

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16
Q

Where are paracrine secretions secreted from?

A

Cells in the mucosa

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17
Q

Where do paracrine secretions act?

A

Locally on adjacent cells via interstitial fluid

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18
Q

What is an example of a paracrine secretion?

A

Somatostatin

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19
Q

What does somatostatin do?

A

Acts on g cells that inhibit gastrin release in the stomach

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20
Q

Where are the 4 places that exocrine secretions happen?

A

Salivary glands, gastric glands, pancreas, liver

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21
Q

What do the salivary glands secrete?

A

Mucus and lipase

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22
Q

What do gastric glands secrete?

A

HCL, pepsin, mucus

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23
Q

What does the pancreas secrete?

A

Bicarbonate ions, enzymes (amylase, lipase, carboxypeptidase)

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24
Q

What does the liver secrete?

A

Bile salts, bile acids

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25
Q

What are endocrine secretions and where are they synthesised?

A

Hormones, synthesised by ductless glands

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26
Q

How do endocrine secretions elicit a response?

A

Enter the bloodstream and travel to the target tissues where they bind to specific receptors

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27
Q

Where is gastrins target?

A

Stomach (specifically G cells in the antrum)

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28
Q

Where is secretins target?

A

Duodenal mucosa

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29
Q

What does secretin do?

A

Balances the acidity from the stomach by telling the pancreas to secrete bicarbonate rich secretions

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30
Q

Where is cholecystokinin targeted?

A

Duodenal mucosa

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31
Q

What is insulin secreted by?

A

Pancreas (beta cells)

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32
Q

What do endo, exo and paracrine secretions allow?

A

Active digestion and control of digestion, gastric motility and energy homeostasis

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33
Q

What food types are transported across the intestinal epithelium into the blood?

A

Glucose and amino acids

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34
Q

What food types are transported into the lymph via lacteals?

A

Fats and lipids

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35
Q

Where does absorption mainly take place?

A

Small intestine

36
Q

What does the colon do?

A

Absorbs 90% of the water

37
Q

How may drugs and some products of normal metabolism leave the body?

A

Saliva, bile, faeces and vomit

38
Q

How do indigestible food particle leave the body?

A

Faeces

39
Q

What are the 7 defence mechanisms in the gut?

A
  • sight, smell and taste
  • vomit reflex
  • acid in stomach
  • mucus secretions
  • natural bacteria flora
  • aggregation of lymphoid tissues
  • peyer’s patches
40
Q

How does acid in the stomach help in defence?

A

Kills most harmful bacteria

41
Q

How does natural flora help in defence?

A

Prevents colonisation of harmful bacteria

42
Q

How does aggregation of lymphoid tissue help in defence?

A

Analyse and respond to pathogenic microbes

43
Q

Where are peyers patches located?

A

In the lamina propria layer of mucosa and extending into the submucosa of the ileum

44
Q

What are the metabolic functions of the liver?

A

Involved in the carb, nitrate and lipoprotein metabolism

Also production of bile and excretion of bilirubin

45
Q

What are the factors and mechanisms involved in the storage and digestion of the gut?

A

Mastication, swallowing, enzymatic digestion, absorption

46
Q

What are the factors and mechanisms involved in the motility of the gut?

A

Peristalsis, mass movement, ACh, motility, NO and VIP

47
Q

What are the factors and mechanisms involved in the defence of the gut?

A

Smell, sight, taste, gastric acid, vomit reflex, mucus, immune response (IgA)

48
Q

What is the name of the nerves that go from the gut muscle to the spinal cords?

A

Splanchnic nerves

49
Q

What is the name of the nerves that go from the gut muscle to the brain and ENS?

A

Afferent and efferent vagal nerves

50
Q

What chemicals mediate contraction in the GI tract?

A

ACh and substance p

51
Q

How does the ANS enable movement of food in the duodenum?

A

Ripples of contraction move the food towards the antrum.

52
Q

When does the pyloric sphincter close?

A

When a peristaltic wave arrives

53
Q

What causes the opening of the pyloric sphincter?

A

Repulsion of chyme

54
Q

What allows mixing/grinding in the duodenum?

A

Repulsion of antral contents backwards towards the body

55
Q

What is the sieving effect?

A

Viscous and solid matter (bigger than 2mm) being retained in the stomach

56
Q

What happens in the fundus?

A

Pacemaker zone, spontaneous depolarisation and BER and peristalsis

57
Q

Where can gastrin act?

A

Either directly on the cells that need to secrete acid

Or bind to histamine secreting ECL cells that act on parietal cells

58
Q

How do ECL cells act on parietal cells?

A

H2

59
Q

What effect does ACh have on parietal cells?

A

Secrete HCl via muscarinic receptors

60
Q

What does ECL cell stand for?

A

Enterochromaffin cell

61
Q

What does hyperacidity do to d cells?

A

Stimulates them to release somatostatin

62
Q

What does the vagovagal reflex describe?

A

The reflex in which both the afferent and efferent axons are in the vagal nerve trunk

63
Q

Where does the vagovagal reflex travel from?

A

Brain stem (medulla)

64
Q

When is the vagovagal reflex active?

A

Receptive relaxation in response to swallowing

65
Q

What does the vagovagal reflex promote?

A

Motility and acid secretion

66
Q

What does DMVN stand for?

A

Dorsal vagal complex nucleus

67
Q

What is the DMVN?

A

Main site of origin of vagal efferents supplying the gut

68
Q

What are the two nerve fibres in the enteric nervous system that are intrinsic to the gut?

A 
Myenteric plexus (Auerbachs) 
Submucosal plexus (meissners)
69
Q

What does the myenteric plexus do?

A

Motor function

70
Q

What does meissners plexus do?

A

Intestinal secretions

71
Q

How are the nerve fibres connected to the CNS?

A

By parasympathetic fibres

72
Q

Do the myenteric and submucosal plexus’ need to be connected to the CNS to work?

A

No- it can be mediated entirely by the ENS

73
Q

What are the 6 neurotransmitters involved in the myenteric and submucosal plexus’?

A

ACh, NO, NA, 5HT, GABA, ATP

74
Q

Where are the two plexuses found?

A

In the wall of the colon

75
Q

Where do the plexuses receive input from?

A

PNS and SNS

76
Q

What effect does the parasympathetic nervous system have on the gut?

A

Increases contraction of proximal colon

77
Q

What effect does the sympathetic nervous system have on the gut?

A

Decreases colonic movement

78
Q

What is the colocolonic reflex?

A

Food products that increase motility

79
Q

Which is the most prominent plexus?

A

Myenteric

80
Q

What effect does cholinergic stimulation have on the myenteric plexus?

A

Increases gastric motility and secretion

81
Q

What effect does adrenergic stimulation have on the myenteric plexus?

A

Decreases gastric motility and secretion

82
Q

What is the timeline of how fast materials ability to be absorbed?

A

Fatty acids> proteins> carbs

83
Q

How do fatty acids in the duodenum decrease gastric emptying?

A

Increasing the contractility of the pyloric sphincter

84
Q

What is peristalsis?

A

A wave of propulsive contractions that moves the contents of the gut towards the anus

85
Q

What initiates contraction?

A

Distension

86
Q

What controls peristalsis?

A

Vagal inhibitory and excitatory fibres

87
Q

What causes relaxation in peristalsis?

A

When NO or VIP is released

Physiology 1 (65 decks)

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