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HUBS192 2024 > Lecture 24: INTRODUCTION AND MOTILITY > Flashcards

Lecture 24: INTRODUCTION AND MOTILITY Flashcards

1
Q

What are the functions of the GI tract?

A

To obtain nutrients required fo growth and energy needs. Also replace fluid and salts lost in urine, faeces, breathing and sweating

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2
Q

What must be regulated?

A

The conditions of the intestinal lumen

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3
Q

Where are receptors found?

A

In the wall of the GI tract

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4
Q

What do the receptors respond to?

A

Stretch when food is in the lumen and change in composition

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5
Q

What may change in composition be?

A

pH, osmolarity, amino acids, sugars and fats

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6
Q

What are the effectors?

A

Smooth muscle and glands

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7
Q

What do the receptors stimulate?

A

Smooth muscle contractions and gland secretion

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8
Q

What regulates GI function?

A

Nervous and hormonal

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9
Q

What does the CNS do?

A

Coordinate activity over long distances fan modulate activity of the enteric nervous system

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10
Q

What does the parasympathetic nervous system do?

A

Stimulate motility and secretion

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11
Q

What does the sympathetic nervous system do?

A

Inhibit motility and secretion

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12
Q

What is the ENS made up of?

A

Submucosal plexus and myenteric plexus

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13
Q

What does the submucosal plexus do?

A

Regulate secretion

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14
Q

What does the myenteric plexus do?

A

Regulate motility

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15
Q

What is the ENS involved in?

A

Local reflexes (involuntary) such as peristalsis and segmentation

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16
Q

Where is the ENS?

A

Total self contained in the GI tract

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17
Q

What is the largest endocrine organ in the body?

A

GI tract

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18
Q

What function does the GI tract have?

A

Endocrine (blood) and paracrine (localised)

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19
Q

What are critical hormones in the GI tract?

A

Gastrin, gastric inhibitory peptide (GIP), secretin and cholecystokinin (CCK)

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20
Q

What are the functions of motility in the GI tract?

A

Movement at a controlled rate, mechanical digestion, mixing and exposure to absorptive surfaces

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21
Q

What does movement at a controlled rate involve?

A

Propulsion and storage

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22
Q

What does movement at a controlled rate aid?

A

Chemical digestion and absorption

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23
Q

What does mechanical digestion do?

A

Increases surface area

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24
Q

What is mechanical digestion essential for?

A

Chemical digestion

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25
Q

What does mixing aid in?

A

Chemical digestion

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26
Q

What does exposure to absorptive surfaces aid?

A

Absorption

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27
Q

What is the basis of GI motility?

A

Smooth muscle

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28
Q

What are the properties of smooth muscle?

A

Spontaneously active (contracts without external input)

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29
Q

What is frequency of smooth muscle contraction regulated by?

A

ENS

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30
Q

What is the frequency of contraction in the stomach?

A

3/min

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31
Q

What is the frequency of contraction in the duodenum?

A

12/min

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32
Q

What is the frequency of contraction in the ileum?

A

9/min

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33
Q

What is the strength of contraction regulated by?

A

Nervous and hormonal input (CNS)

34
Q

What is the motility pattern during fasting?

A

Migrating motor complex

35
Q

When does the migrating motor complex happen?

A

4 hours after a meal

36
Q

When does the migrating motor complex repeat?

A

Every 2 hours until eat again

37
Q

What is the purpose of the migrating motor complex?

A

Housekeeping (remove residual secretions and undigested materials)

38
Q

What are the motility patterns during feeding?

A

Storage, propulsion and mixing

39
Q

Where does storage occur?

A

Stomach and colon

40
Q

What does relaxation of smooth muscle allow?

A

Volume to increase without changing pressure

41
Q

Where does propulsion occur?

A

Esophagus, stomach, small and large intestine

42
Q

What is propulsion known as?

A

Peristalsis

43
Q

What happens in peristalsis?

A

Smooth muscle contracts behind the bolus and pushes it forward

44
Q

Where does mixing occur?

A

Stomach, small and large intestine

45
Q

What is the mixing in the stomach?

A

Retropulsion

46
Q

What is the mixing in the small and large intestine?

A

Segmentation

47
Q

What happens in segmentation?

A

Alternate patterns of contraction to push food together and apart (mix it)

48
Q

What is the purpose of chewing?

A

To reduce the size of food

49
Q

What does reducing the size of food do?

A

Allows injection and mixes food with saliva to allow taste

50
Q

Is chewing voluntary?

A

Yes, skeletal muscle of the jaw

51
Q

What about chewing is involuntary?

A

Strength, frequency and side

52
Q

What is swallowing?

A

Rapid transfer of material from mouth to stomach

53
Q

How is swallowing initiated?

A

Voluntarily but proceeds reflexly

54
Q

Where does storage occur in the stomach?

A

Fundus and body

55
Q

Where does mechanical digestion occur in the stomach?

A

Antrum

56
Q

Where does mixing occur in the stomach?

A

Antrum

57
Q

How is there controlled delivery to the duodenum?

A

By the pyloric sphincter

58
Q

What size does the stomach drink to when fasting?

A

50 ml

59
Q

What does the migratory motor complex involve?

A

1 hour of inactivity, 50 min of uncoordinated activity and 10 min of coordinated activity

60
Q

What happens during feeding (storage)?

A

Receptive relaxation and gastric accommodation

61
Q

What is storage under regulation of?

A

Nervous (vagus nerve - parasympathetic)

62
Q

Where is peristalsis initiated in the stomach?

A

The greater curvature and spreads to the antrum

63
Q

How is peristalsis during the first 60 minutes after eating?

A

Gentle

64
Q

How is peristalsis during 60-300 minutes after eating?

A

Intense

65
Q

What is retropulsion?

A

A combination of peristalsis and closure of the pyloric sphincter causing food to collide and mix/break down

66
Q

What is gastric emptying a result of?

A

Motility

67
Q

What does the rate of gastric emptying match?

A

The digestive capacity of the intestine

68
Q

What is gastric emptying regulated by?

A

Feedback from duodenum

69
Q

What factors affect gastric emptying?

A

Size of meal -larger means faster emptying and composition of meal

70
Q

What empties faster?

A

Fluids faster than solids

71
Q

What are slow to digest?

A

Fats so slow gastric emptying

72
Q

What happens when there is fatty, hypertonic, acidic chyme in the duodenum?

A

Duodenal entero-endocrine cells secrete enterogastones (secretin and cholycystokinin) and the chemoreceptors and stretch receptors trigger the enterogastric reflex

73
Q

What happens in the enterogastric reflex?

A

Short reflex via enteric neurons and long reflex via CNS centres increases sympathetic activity and decreases parasympathetic activity

74
Q

What is the overall result of fats being in the duodenum?

A

Decreased contractile force and rate of emptying of the stomach

75
Q

What is the functions of small intestine motility?

A

Mixing with secretions from pancreas, biliary system (liver, gall bladder) and intestine, controlled movement and exposure of products of digestion to absorptive surfaces (epithelial cells)

76
Q

What is the motility pattern of small intestine after a meal?

A

Segmentation for mixing, exposure to absorptive surfaces and all movement. Limited peristalsis for movement in humans

77
Q

What does the colon store?

A

Faeces

78
Q

What organ of the GI tract has large periods of inactivity?

A

Large intestine/colon

79
Q

What does segmentation in the large intestine do?

A

Exposure to absorptive surfaces and absorption of fluid and salt from faeces

80
Q

When does mass movement occur?

A

1-2 times a day following meals

81
Q

How does mass movement occur?

A

A peristaltic wave

82
Q

What does a peristaltic wave do?

A

Drives faeces into the rectum and initiates defecation

HUBS192 2024 (38 decks)

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