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HUBS192 > 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
What does mixing aid in?
Chemical digestion
26
What does exposure to absorptive surfaces aid?
Absorption
27
What is the basis of GI motility?
Smooth muscle
28
What are the properties of smooth muscle?
Spontaneously active (contracts without external input)
29
What is frequency of smooth muscle contraction regulated by?
ENS
30
What is the frequency of contraction in the stomach?
3/min
31
What is the frequency of contraction in the duodenum?
12/min
32
What is the frequency of contraction in the ileum?
9/min
33
What is the strength of contraction regulated by?
Nervous and hormonal input (CNS)
34
What is the motility pattern during fasting?
Migrating motor complex
35
When does the migrating motor complex happen?
4 hours after a meal
36
When does the migrating motor complex repeat?
Every 2 hours until eat again
37
What is the purpose of the migrating motor complex?
Housekeeping (remove residual secretions and undigested materials)
38
What are the motility patterns during feeding?
Storage, propulsion and mixing
39
Where does storage occur?
Stomach and colon
40
What does relaxation of smooth muscle allow?
Volume to increase without changing pressure
41
Where does propulsion occur?
Esophagus, stomach, small and large intestine
42
What is propulsion known as?
Peristalsis
43
What happens in peristalsis?
Smooth muscle contracts behind the bolus and pushes it forward
44
Where does mixing occur?
Stomach, small and large intestine
45
What is the mixing in the stomach?
Retropulsion
46
What is the mixing in the small and large intestine?
Segmentation
47
What happens in segmentation?
Alternate patterns of contraction to push food together and apart (mix it)
48
What is the purpose of chewing?
To reduce the size of food
49
What does reducing the size of food do?
Allows injection and mixes food with saliva to allow taste
50
Is chewing voluntary?
Yes, skeletal muscle of the jaw
51
What about chewing is involuntary?
Strength, frequency and side
52
What is swallowing?
Rapid transfer of material from mouth to stomach
53
How is swallowing initiated?
Voluntarily but proceeds reflexly
54
Where does storage occur in the stomach?
Fundus and body
55
Where does mechanical digestion occur in the stomach?
Antrum
56
Where does mixing occur in the stomach?
Antrum
57
How is there controlled delivery to the duodenum?
By the pyloric sphincter
58
What size does the stomach drink to when fasting?
50 ml
59
What does the migratory motor complex involve?
1 hour of inactivity, 50 min of uncoordinated activity and 10 min of coordinated activity
60
What happens during feeding (storage)?
Receptive relaxation and gastric accommodation
61
What is storage under regulation of?
Nervous (vagus nerve - parasympathetic)
62
Where is peristalsis initiated in the stomach?
The greater curvature and spreads to the antrum
63
How is peristalsis during the first 60 minutes after eating?
Gentle
64
How is peristalsis during 60-300 minutes after eating?
Intense
65
What is retropulsion?
A combination of peristalsis and closure of the pyloric sphincter causing food to collide and mix/break down
66
What is gastric emptying a result of?
Motility
67
What does the rate of gastric emptying match?
The digestive capacity of the intestine
68
What is gastric emptying regulated by?
Feedback from duodenum
69
What factors affect gastric emptying?
Size of meal -larger means faster emptying and composition of meal
70
What empties faster?
Fluids faster than solids
71
What are slow to digest?
Fats so slow gastric emptying
72
What happens when there is fatty, hypertonic, acidic chyme in the duodenum?
Duodenal entero-endocrine cells secrete enterogastones (secretin and cholycystokinin) and the chemoreceptors and stretch receptors trigger the enterogastric reflex
73
What happens in the enterogastric reflex?
Short reflex via enteric neurons and long reflex via CNS centres increases sympathetic activity and decreases parasympathetic activity
74
What is the overall result of fats being in the duodenum?
Decreased contractile force and rate of emptying of the stomach
75
What is the functions of small intestine motility?
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
What is the motility pattern of small intestine after a meal?
Segmentation for mixing, exposure to absorptive surfaces and all movement. Limited peristalsis for movement in humans
77
What does the colon store?
Faeces
78
What organ of the GI tract has large periods of inactivity?
Large intestine/colon
79
What does segmentation in the large intestine do?
Exposure to absorptive surfaces and absorption of fluid and salt from faeces
80
When does mass movement occur?
1-2 times a day following meals
81
How does mass movement occur?
A peristaltic wave
82
What does a peristaltic wave do?
Drives faeces into the rectum and initiates defecation

HUBS192 (38 decks)

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