5.3.5. Overview of the Stomach - Gastric Motility Flashcards
What is the name of the Waves which travel down from the Oesophagus?
Peristaltic Waves
What controls the Peristaltic Waves?
The Muscularis Externa and the Myentaric nerve plexus
Do the Peristaltic Waves from the Oesophagus continue throughout the Stomach?
Yes
What is the fucntion of the Peristaltic Waves?
Mixing of Gastric contents
What are the Peristaltic Waves used for in the Fundus of the Stomach?
No mixing occurs here - There is only thin Smooth Muscle which is primarily for Stretch Capacity
What are the Peristaltic Waves used for in the Body of the Stomach?
No mixing occurs here - There is only thin Smooth Muscle so there is little contractile strength
What are the Peristaltic Waves used for in the Antrum of the Stomach?
Mixing occurs here as the muscle is thick, leading to powerful contractions.
What does the Thick Muscle of the Antrum also allow?
Strict control of the Volume of Chyme which enters into the Duodenum, at the Pyloric Sphincter
What does strict control of the Volume of Chyme Entering into the Duodenum allow for?
- Small Quantities of Chyme entering the Duodenum
2. Further mixing of the Gastric Contents at the Antrum
What happens to the Antral Contents as the Pyloric Sphincter contracts?
It is forced to the back of the Stomach, as the contractions of Peristaltic Waves still occur
Why is the Mixing of Contents essential?
It allows for the Neutralization of Gastric Acid and Pepsin before the Chyme enters into the Duodenum
What generates the Gastric Peristaltic Rhythm?
Pacemaker Cells in the Longitudinal Muscle Layer of the Muscularis Externa
What is the rough rate of the Peristaltic Waves?
1 wave every 20 seconds
What are Slow Waves?
The standard Peristaltic Rhythm. Around 3 waves per minute
How are Slow Waves produced?
The Spontaneous Depolarization and Repolarization of Pacemaker Cells
Where are the Pacemaker Cells found?
In the Longitudinal Muscle Layer of the Muscularis Externa
How is the Potential Difference (Signal) Passed from Cell to Cell?
Via Gap-Junctions
What is the Slow Wave Rhythm also known as?
The Basic Electrical Rhythm (BER)
Is the Basic Electrical Rhythm higher in the Proximal or Distal parts of the Alimentary Tract?
Proximal
i.e. it is faster in the Stomach than it is in the Ileum
Is Slow Wave Depolarization at the Level of Threshold or Sub-Threshold?
Sub-Threshold
What is the result of the Slow Wave Depolarization being Sub-Threshold?
Further Depolarization is required
What can provide further depolarization so the Slow Waves can be emitted?
- Acetylcholine from the Vagus Nerve
2. Gastrin from the G-Cells
How do the Action Potentials create a stronger contraction?
It is the frequency of Action Potentials which increases the Strength of Contraction
Other that the production of Gastric Acid, what else can Gastrin Stimulate?
An increase in the Strength of Contraction
What increases the release of Acetylcholine and Gastrin?
Distension of the Stomach Wall
How does Distension of the Stomach Wall result in an increase of Acetylcholine and Gastrin?
There is an increase in Short and Long Reflexes
