Exam #5: Gastric Motility Flashcards
What is the migrating motor complex?
GI motor activity that starts in the stomach and sweeps over the upper GI tract ~Q90min in the unfed state
What are the three general types of motor activity in the stomach?
1) Storage= reservoir
2) Churning= mixing & initiation of digestion
3) Emptying= delivery of food to the duodenum
What is receptive relaxation?
This is a vagovagal reflex that is initiated by swallowing; there is a reflexive relaxation of the stomach in anticipation of the food bolus
*****Allows for a rise in volume without a rise in pressure
What mediates receptive relaxation?
Vagovagal reflex that is described as “Non-cholingeric/ Non-adrenergic”
What does Non-cholingeric/ Non-adrenergic mean?
This is a kind of archaic term that typically refers to the action of NO, before it was known that NO played a role
What is gastric accommodation?
This is stomach relaxation in response to gastric filling i.e. now stomach contents stretching the walls of the stomach lead to the release of NO that causes a relaxation of the stomach
What are the two steps of gastric storing/ filling?
1) Receptive relaxation
2) Gastric accomodation
What are the three parts of gastric churning?
1) Propulsion
2) Retropulsion
3) Grinding
What is propulsion?
Movement of the contents toward the antrum/ pylorus
*****Note that the pylorus is closed
What initiates propulsion?
Pacemaker cells near the greater curvature
What happens after propulsion?
Propulsion of food against the closed pylorus results in pulverization and shearing of food
What is grinding?
This is the process by which food is trapped in the antrum & food products smaller than 2mm pass through the pylorus
What determines the rate of gastric emptying?
Content of the ingested material
- Liquid is fastest
- Glucose solution
- Protein and fat breakdown slowest
What controls the rate of gastric emptying?
Neuronal & hormonal regulation
What are the hormones that control gastric emptying? Summarize the stimuli that cause their secretion.
Secretin= HCl- duodenum CCK= Fat- duodenum Gastrin= Protein- stomach
What is the stimulus for Secretin secretion? What is the function of Secretin?
- HCl in duodenum results in delayed gastric emptying
- This is a protective
What is the stimulus for CCK secretion? What is the function of CCK?
- Fat in the duodenum stimulates the release of CCK
- CCK feedback delays gastric emptying
This allows for efficient breakdown of the meal & increases the surface area for digestion
What is the stimulus for Gastrin secretion? What is the function of Gastrin?
- Protein in the stomach induces the release of gastrin
- Gastrin delays gastric emptying to increase the efficiency of protein digestion in the stomach
What is the role of duodenal distension?
Duodenal distention results in negative feedback on the stomach mediated by the ENS to delay gastric emptying
What are the effect of ACh, opoids, and 5-HT on gastric emptying?
Delay
What is the effect of NO & VIP on gastric emptying?
Promotion of gastric emptying
What is gastroparesis?
Simply, gastroparesis= impaired motility
**Note that this is NOT a COMPLETE PARALYSIS; rather, a disruption of normal coordinated activity that leads to a delay in emptying that is more often NEURONAL in origin (vs. hormonal)
Outline the emetic response.
1) Numerous peripheral stimuli converge on the emetric center in the medulla
2) Vomiting reflex
- reverse peristalsis in small intestine
- relax stomach
- forced inspiration
- sphincter relaxation
- expulsion
*****This reflex is under the control of: 5-HT, ACh, DA & Histamine
Why is there increased salivary secretion prior to an emetic event?
This increased salivary production is protective, as it contains:
- HCO3-
- Mucin
