Gastric Physiology Flashcards
What are the two primary functional activities of the stomach?
Propulsion and secretion & digestion
Which of the following is NOT a motor function of the stomach?
Absorption of nutrients
Receptive relaxation occurs in which part of the stomach?
Proximal stomach
Which nerve is responsible for signaling receptive relaxation?
Vagus nerve
What neurotransmitter is released by inhibitory enteric nerves to relax the proximal stomach?
Non-adrenergic non-cholinergic (NANC) transmitters
What happens if the vagus nerve to the proximal stomach is cut?
Decreased receptive relaxation, leading to abdominal discomfort
What is the primary type of contractile activity in the distal stomach?
Peristalsis
What determines the amplitude of a peristaltic wave in the stomach?
The amount of stretch in the stomach wall
What is the frequency of Basic Electrical Rhythm (BER) in the stomach?
3 waves per minute
Which of the following is true regarding Electrical Response Activity (ERA)?
It initiates muscle contraction
What type of cells act as pacemakers for gastric slow waves?
Interstitial cells of Cajal
What happens when the pyloric sphincter closes due to antral peristalsis?
Retropulsion occurs, enhancing mixing and breakdown
Which of the following statements about gastric emptying of liquids is true?
It occurs due to a pressure gradient between the proximal stomach and duodenum
What effect does a vagotomy to the proximal stomach have on gastric emptying of liquids?
Accelerated emptying due to increased pressure gradient
Which factor would NOT slow down gastric emptying?
Increased gastric stretch
Which hormones inhibit antral peristalsis and slow gastric emptying?
Secretin and CCK
What are the conditions that can lead to disorders of gastric emptying?
Increased pressure, decreased pressure, increased resistance, central factors
What is the role of the pyloric sphincter?
Behaves as a filter and regulates gastric emptying
What is the function of HCl in gastric juice?
Precipitates soluble proteins, denatures proteins, activates pepsin
What is the primary secretion of parietal cells?
HCl and intrinsic factor
What is a ‘postprandial alkaline tide’?
Temporary increase in urine pH after a meal
What is the function of intrinsic factor?
Required for vitamin B12 absorption in ileum
What condition is caused by intrinsic factor deficiency?
Pernicious anemia
What protects the gastric mucosa?
Gastric mucosal barrier (GMB)
What factors contribute to ulcer formation?
Normal HCl output with weak barrier, excessive HCl output
What is the role of mucus in the stomach?
Protects the mucosa and lubricates
Fill in the blank: The stomach’s secretions include HCl, pepsinogen, intrinsic factor, and _______.
Mucin
True or False: The pyloric sphincter is closed at rest.
False
Which cells secrete pepsinogen?
Chief cells
What is the role of H+ in the gastric mucosal barrier (GMB)?
H+ will combine with HCO3- in the mucous gel layer to form water and CO2
This indicates that GMB is impermeable to H+.
What are the components of the gastric mucosal barrier (GMB)?
Apical surfaces and tight junctions
These components help protect the gastric mucosa.
How does the gastric mucosa maintain its protection?
Through rapid cell turnover
New surface epithelial cells are produced to replace old ones very rapidly.
What factors contribute to ulcer formation?
Normal HCl Output, Weak Barrier; Aspirin and NSAIDs; Helicobacter pylori; Normal Barrier, Excessive HCl Output; Gastrin-producing tumours
These factors disrupt the balance necessary for a healthy gastric environment.
What are the effects of prostaglandins on the gastric mucosa?
- Increase mucin and bicarb secretion
- Increase blood flow
- Decrease acid production
- Increase epithelial cell turnover
Prostaglandins play a protective role in the gastric mucosa.
Why can ASA and NSAIDs cause gastric ulcers?
They destroy the gastric mucosal barrier and inhibit prostaglandin synthesis
This leads to loss of cytoprotection and cellular damage.
What is the local effect of ASA and NSAIDs on the gastric mucosa?
They destroy the gastric mucosal barrier
This can lead to leakage into gastric epithelial cells and cause cellular damage and apoptosis.
What is the systemic effect of ASA and NSAIDs on gastric mucosal protection?
They inhibit prostaglandin synthesis
This results in the gastric mucosa losing cytoprotection.
