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4. GI Flashcards > Gastric Motility > Flashcards

Gastric Motility Flashcards

1
Q

What is the volume of an empty stomach?

A

50ml

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2
Q

When eating, how much can the stomach accomodate?

A

1.5L with little increase in luminal pressure

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3
Q

How does the stomach vol increase with little increase in luminal pressure?

A

It does this by the smooth muscles in the body and fundus undergo receptive relaxation

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4
Q

What is receptive relaxation mediated by?

A

Mediated by parasympathetic NS acting on enteric nerve plexus

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5
Q

Where is co ordination for receptive relaxation found?

A

Afferent Input from stomach via vagus nerve and swallowing centre in brain

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6
Q

What is released by the enteric nerves to mediate relaxation?

A

Nitric oxide & serotonin

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7
Q

What does acetyl choline do in regards to receptive relaxation?

A

ACh activates parietal & chief cells and initiates receptive relaxation

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8
Q

What happens in peristalsis?

A

Peristaltic waves begin in the gastric body
Weak contraction in body (little mixing of luminal contents with acid and pepsin)

More powerful contraction in gastric antrum
Pyloric sphincter (ring of smooth muscle &connective tissue between the antrum and duodenum)closes as peristaltic wave reaches it

Little chyme enters duodenum
Antral contents forced back towards body (more mixing=digestion)

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9
Q

What is the frequency of the peristaltic waves determined by?

A

Pacemaker cells (interstitial cells of cajal) in the muscular propria (longitudinal smooth muscle)

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10
Q

How much chyme enters the duodenum at a time?

What happens to the rest?

A

Only 3ml

rest is pushed back to stomach

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11
Q

How often do the peristaltic waves take place?

A

Constant - 3 per min

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12
Q

What do pacemaker cells undergo?

A

Slow depolarization-repolarisation cycles

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13
Q

Where do the depolarization waves transmit through?

What do these not cause?

A

Gap junctions to adjacent smooth muscle

Significant contraction in the empty stomach

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14
Q

How does the strength of the peristaltic contraction vary?

A

Excitatory neurotransmitters & hormones further depolarize membranes
Action potentials are generated when threshold is reached

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15
Q

How can the action potential threshold for muscle contraction be altered?

A

The interstitial cells of cajal are active all the time, but the action potential threshold can be altered by the enteric NS

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16
Q

Where are strength of contractions increased by? (2)

A 
Gastrin
Gastric distension (mediated by mechano receptors)
17
Q

What are strength of contractions decreased by?

A 
Duodenal distension 
Increase in duodenal fat
Increase in duodenal osmolarity
Decrease in duodenal pH
Increase in sympathetic NS stimulation 
Decrease in parasympathetic NS stimulation
18
Q

Does the stomach or duodenum have a greater capacity?

A

Capacity of stomach is greater than duodenal capacity

19
Q

What happens when the duodenum is overfilled by a hypertonic solution?

A

Causes dumping syndrome

Vomiting, bloating, cramps, diorrhoea, dizziness, fatigue, weakness, sweating

20
Q

What happens as gastric contents enter duodenum?

A

Duodenal pH falls

21
Q

What is gastroparesis?

A

Delayed gastric emptying

food rots in stomach

22
Q

What can gastroparesis be caused by?

A 
Idiopathic (unknown cause)
Autonomic neuropathies (eg. Diabetes mellitus)
Drugs
Abdominal surgery
Parkinson’s disease 
Multiple sclerosis 
Scleroderma 
Amyloidosis
Females
23
Q

What drugs can cause gastroparesis?

A 
H2 receptor antagonists
Proton pump inhibitors
Opioid analgesics
Beta adrenergic receptor agonists 
Calcium channel blockers
Levodopa
24
Q

What are the symptoms of delayed gastric emptying?

A 
Nausea
Early satiety (feeling full early) 
Vomiting undigested food 
Cause matter in stomach to rot and smell-similar to faeces in looks 
GORD
Abdo pain/bloating
Anorexia
25
Q

What is duodenal emptying slowed by?

A

Decreased pH
Increased FA & AA
Distension
Hypertonicity

26
Q 
What does
Decreased pH
Increased FA & AA
Distension
Hypertonicity
Which causes slowed duodenal emptying stimulate?
A 
short pathway (smaller response) - enteric local GI neurones
long pathway, CNS, bigger
27
Q

Why does duodenal emptying need to be slowed?

A

as volume of duodenum is smaller than stomach

4. GI Flashcards (13 decks)

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