8.3

Question 1

What are the two mechanisms by which saliva secretion is controlled? Describe the passage of this nervous signal

Answer 1

• Conditioned and simple reflexes
• Medulla -> autonomic nerves -> salivary glands

Question 2

If ICC slow waves are successfully turned into action potentials, then what direction does the contraction sweep from?

Answer 2

Fundus to antrum

Question 3

What local factors in the stomach increase gastric motility? How?

Answer 3

• Volume of chyme (i.e., distension) and fluidity
• Smooth muscle stretch, intrinsic plexuses, vagus nerve, hormone gastrin

Question 4

What factors in the duodenum influence gastric motility? How?

Answer 4

• Fat, Acid, Hypertonicity, Distension
• Enterogastric reflex (and enterogastrones: CCK and secretin), intrinsic and extrinsic nerves

Question 5

How can external factors outside the duodenum inhibits antral motility?

Answer 5

Emotion and pain can increase sympathetic activity, thus decreasing antral motility

Question 6

Simplified vomiting mech

Answer 6

• Coordinated by vomiting centre in medulla
• Deep inspiration, glottis closed
• Gastroesophageal and pharyngoesophageal sphincter are relaxed
• Respiratory muscles contract, squeezing stomach contents out

Question 7

What is the function of mucous in the stomach?

Answer 7

• Lubrication
• Pepsin inhibition
• Neutralizing acids to prevent injury

Question 8

What do chief cells release, and what stimulates this?

Answer 8

• Pepsinogen
• Stimulated by ACh and Gastrin

Question 9

What do parietal cells release, and what stimulates this?

Answer 9

• Intrinsic factor and HCl
• ACh, gastrin, histamine

Question 10

What do mucous cells release, and what stimulates this?

Answer 10

• Alkaline mucus
• Mechanical stimulation

Question 11

What do Enterochromaffin like cells release? What stimulates this? What does the secretion do?

Answer 11

• Release histamine
• Stimulated by ACh and Gastrin
• Stimulates parietal cells

Question 12

What do G cells release? What does this do? What stimulates it?

Answer 12

• Secrete gastrin
• Stimulates parietal, chief, and ECL cells
• Stimulated by ACh

Question 13

What do D cells release? What stimulates this? What do these secretions do?

Answer 13

• Release somatostatin
• Stimulated by Acid
• Inhibits parietal, G, and ECL cells

Question 14

What are the three phases of gastric secretion? Describe them.

Answer 14

• Cephalic (increased gastric secretion in response to thinking about eating food)
• Gastric (increased gastric secretion due to proteins activating chemoreceptors, stimulating intrinsic nerves and G cells)
• Intestinal (Inhibition of gastric secretion and motility as chyme is processed in the small intestine)