5.3.5. Overview of the Stomach - Gastric Motility

Question 1

What is the name of the Waves which travel down from the Oesophagus?

Answer 1

Peristaltic Waves

Question 2

What controls the Peristaltic Waves?

Answer 2

The Muscularis Externa

Question 3

Do the Peristaltic Waves from the Oesophagus continue throughout the Stomach?

Answer 3

Yes

Question 4

What is the Action of the Peristaltic Waves?

Answer 4

The Mixing of Gastric Products

Question 5

What are the Peristaltic Waves used for in the Fundus of the Stomach?

Answer 5

No mixing occurs here - There is only thin Smooth Muscle which is primarily for Stretch Capacity

Question 6

What are the Peristaltic Waves used for in the Body of the Stomach?

Answer 6

No mixing occurs here - There is only thin Smooth Muscle so there is little contractile strength

Question 7

What are the Peristaltic Waves used for in the Antrum of the Stomach?

Answer 7

Mixing occurs here as the muscle is thick, leading to powerful contractions.

Question 8

What does the Thick Muscle of the Antrum also allow?

Answer 8

Strict control of the Volume of Chyme which enters into the Duodenum, at the Pyloric Sphincter

Question 9

What does strict control of the Volume of Chyme Entering into the Duodenum allow for?

Answer 9

1. Small Quantities of Chyme entering the Duodenum

2. Further mixing of the Gastric Contents as the Antrum

Question 10

What happens to the Antral Contents as the Pyloric Sphincter contracts?

Answer 10

It is forced to the back of the Stomach, as the contractions of Peristaltic Waves still occur

Question 11

Why is the Mixing of Contents essential?

Answer 11

It allows for the Neutralization of Gastric Acid and Pepsin before the Chyme enters into the Duodenum

Question 12

What generates the Gastric Peristaltic Rhythm?

Answer 12

Pacemaker Cells in the Longitudinal Muscle Layer of the Muscularis Externa

Question 13

What is the rough rate of the Peristaltic Waves?

Answer 13

1 wave every 20 seconds

Question 14

What are Slow Waves?

Answer 14

The standard Peristaltic Rhythm

Question 15

How are Slow Waves produced?

Answer 15

The Spontaneous Depolarization and Repolarization of Pacemaker Cells

Question 16

Where are the Pacemaker Cells found?

Answer 16

In the Longitudinal Muscle Layer of the Muscularis Externa

Question 17

How is the Potential Difference (Signal) Passed from Cell to Cell?

Answer 17

Via Gap-Junctions

Question 18

What is the Slow Wave Rhythm also known as?

Answer 18

The Basic Electrical Rhythm (BER)

Question 19

Is the Basic Electrical Rhythm higher in the Proximal or Distal parts of the Alimentary Tract?

Answer 19

Proximal

i.e. it is faster in the Stomach than it is in the Ileum

Question 20

Is Slow Wave Depolarization at the Level of Threshold or Sub-Threshold?

Answer 20

Sub-Threshold

Question 21

What is the result of the Slow Wave Depolarization being Sub-Threshold?

Answer 21

Further Depolarization is required

Question 22

What can provide further depolarization so the Slow Waves can be emitted?

Answer 22

1. Acetylcholine from the Vagus Nerve

2. Gastrin from the G-Cells

Question 23

How do the Action Potentials create a stronger contraction?

Answer 23

It is the frequency of Action Potentials which increases the Strength of Contraction

Question 24

Other that the production of Gastric Acid, what else can Gastrin Stimulate?

Answer 24

An increase in the Strength of Contraction

Question 25

What increases the release of Acetylcholine and Gastrin?

Answer 25

Distension of the Stomach Wall

Question 26

How does Distension of the Stomach Wall result in an increase of Acetylcholine and Gastrin?

Answer 26

There is an increase in Short and Long Reflexes