SCT III - Gastrointestinal Tract: Motility

Question 1

How is gut motility controlled?

Answer 1

Myogenic
- Has its own rhythm
- Contract, relax, contract, relax

Neurogenic
- Controlled by neurons (Autonomic, Enteric)

Hormonal
- Gastrin, secretin, CCK, motilin, etc.

Question 2

What are the pacemakers of the GI tract?

Answer 2

Interstitial cells of Cajal

Question 3

Name the muscles responsible for chewing

Answer 3

1. Temporal M.
2. Masseter M.
3. Lateral Pterygoid M.
4. Medial Pterygoid M.

All innervated by Trigeminal N. (CN V) (nAChR)

Question 4

Where are the swallowing centers in the brain?

Answer 4

Medulla Oblongata & Pons

Question 5

What is deglutitive inhibition?

Answer 5

A wave of relaxation prior to contraction

Question 6

How is the deglutitive inhibition regulated?

Answer 6

Deglutitive Inhibition
M. Relax: NO
M. Contract: ACh

Question 7

What induces secondary peristalsis?

Answer 7

Distension caused by stuck food in the esophagus

Question 8

What are the functional regions of the stomach and what are their functions?

Answer 8

Orad
- Contracted at all times
- Relax for food storage

Caudad
- Phasic contractions (propulsion/mixing of food)

Question 9

Where exactly can you find the stomach pacemakers?

Answer 9

In the junction between Orad and Caudad

Question 10

What are the possible feedback relaxation methods of the stomach?

Answer 10

Receptive
- Stomach prepares to receive food & relaxes
- Vagovagal

Adaptive
- Stomach receives food & relaxes
- Vagovagal

Feedback
- Small bowel receives food, stomach relaxes to store

Question 11

What induces stomach relaxation

Answer 11

NANC (VIP, NO, etc.)

Question 12

What happens during delayed emptying of the stomach?

Answer 12

1. Orad relaxes
2. Caudad has less contractions (to not push food towards bowel)
3. Pylorus closes
4. Duodenum narrows (accepts less food)

Question 13

What happens during rapid emptying of the stomach?

Answer 13

1. Orad contracts
2. Caudad has more contractions (to further food towards bowel)
3. Pylorus relaxes and stays open
4. Duodenum remains open to accept more food

Question 14

What is the purpose of the migrating motor complex?

Answer 14

It’s activated when not eating; to clean up the GI tract:
1. Resting
2. Minor waves
3. Very rapid paristalsis contractions

Question 15

What are the two different contraction patterns?

Answer 15

Segmentation
- Mix & break up food

Peristalsis
- Propulsion of food

Question 16

What is disinhibition?

Answer 16

Inhibition of an inhibition

Question 17

How does the ileocecal sphincter/valve prevent backflow of food?

Answer 17

Ileal distension = sphincter relax
Cecal distension = sphincter contract

Question 18

What is the effect of gastrin on sphincters?

Answer 18

Gastrin induces sphincter relaxation

Question 19

What is the effect of opioids on the GI tract?

Answer 19

Inhibit and slow down everything

Question 20

Defecation reflex drawing

Answer 20

Question 21

What happens to sympathetic tone during defecation?

Answer 21

SNS reduced

Question 22

What is active incontinency?

Answer 22

Damage of descending pathways (loss of voluntary control)

You feel it before it happens

Question 23

What is passive incontinency?

Answer 23

Damage to the reflex arc

You don’t even feel it…

Question 24

What are the actions coordinated by the vomiting center?

Answer 24

Medulla Oblongata
- Retroperistalsis
- Sphincters relaxed
- Tachycardia
- Sweating
- Respiratory inhibition
- Contractions of abdominal and thoracic muscles

Question 25

What induces gallbladder contraction?

Answer 25

Contraction
CCK & Gastrn
Cholinergic effect (mAChR)

Sphincter of Oddi
CCK
VIP
Preggn Vagal