SCT III - Gastrointestinal Tract: Motility Flashcards
How is gut motility controlled?
Myogenic
- Has its own rhythm
- Contract, relax, contract, relax
Neurogenic
- Controlled by neurons (Autonomic, Enteric)
Hormonal
- Gastrin, secretin, CCK, motilin, etc.
What are the pacemakers of the GI tract?
Interstitial cells of Cajal
Name the muscles responsible for chewing
- Temporal M.
- Masseter M.
- Lateral Pterygoid M.
- Medial Pterygoid M.
All innervated by Trigeminal N. (CN V) (nAChR)
Where are the swallowing centers in the brain?
Medulla Oblongata & Pons
What is deglutitive inhibition?
A wave of relaxation prior to contraction
How is the deglutitive inhibition regulated?
Deglutitive Inhibition
M. Relax: NO
M. Contract: ACh
What induces secondary peristalsis?
Distension caused by stuck food in the esophagus
What are the functional regions of the stomach and what are their functions?
Orad
- Contracted at all times
- Relax for food storage
Caudad
- Phasic contractions (propulsion/mixing of food)
Where exactly can you find the stomach pacemakers?
In the junction between Orad and Caudad
What are the possible feedback relaxation methods of the stomach?
Receptive
- Stomach prepares to receive food & relaxes
- Vagovagal
Adaptive
- Stomach receives food & relaxes
- Vagovagal
Feedback
- Small bowel receives food, stomach relaxes to store
What induces stomach relaxation
NANC (VIP, NO, etc.)
What happens during delayed emptying of the stomach?
- Orad relaxes
- Caudad has less contractions (to not push food towards bowel)
- Pylorus closes
- Duodenum narrows (accepts less food)
What happens during rapid emptying of the stomach?
- Orad contracts
- Caudad has more contractions (to further food towards bowel)
- Pylorus relaxes and stays open
- Duodenum remains open to accept more food
What is the purpose of the migrating motor complex?
It’s activated when not eating; to clean up the GI tract:
1. Resting
2. Minor waves
3. Very rapid paristalsis contractions
What are the two different contraction patterns?
Segmentation
- Mix & break up food
Peristalsis
- Propulsion of food
What is disinhibition?
Inhibition of an inhibition
How does the ileocecal sphincter/valve prevent backflow of food?
Ileal distension = sphincter relax
Cecal distension = sphincter contract
What is the effect of gastrin on sphincters?
Gastrin induces sphincter relaxation
What is the effect of opioids on the GI tract?
Inhibit and slow down everything
Defecation reflex drawing
What happens to sympathetic tone during defecation?
SNS reduced
What is active incontinency?
Damage of descending pathways (loss of voluntary control)
You feel it before it happens
What is passive incontinency?
Damage to the reflex arc
You don’t even feel it…
What are the actions coordinated by the vomiting center?
Medulla Oblongata
- Retroperistalsis
- Sphincters relaxed
- Tachycardia
- Sweating
- Respiratory inhibition
- Contractions of abdominal and thoracic muscles
What induces gallbladder contraction?
Contraction
CCK & Gastrn
Cholinergic effect (mAChR)
Sphincter of Oddi
CCK
VIP
Preggn Vagal
