GI system: L31 - Revision lecture + Neurohormonal mechanisms Flashcards Preview

HUBS192 L20-42 > GI system: L31 - Revision lecture + Neurohormonal mechanisms > Flashcards

Flashcards in GI system: L31 - Revision lecture + Neurohormonal mechanisms Deck (6)
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1
Q

What is the difference between the Enteric Nervous System and Central Nervous system in terms of neural regulation of the GI system?

A

The ENS is the primary neural system for controlling GI function and is independent - short, local, GI reflexes. The CNS modulates activity of ENS and has long neural reflexes.

2
Q

What is the role of the ENS in GI regulation?

A

Consists of submucosal plexus (at the submucosal layer) which regulates secretion, and myenteric plexus (at the smooth muscle layer) regulates motility.

3
Q

How are GI reflexes initiated? How is this mediated?

A

Distension, acidity of chyme, osmolarity of chyme, presence of products of digestion. Mechanoreceptors (distension), chemoreceptors (composition of lumen), osmoreceptors (osmolarity of lumen).

4
Q

What is the role of CNS in GI regulation?

A

This is extrinsic (outside walls of GI tract) bidirectional regulation of GI function. Parasympathetic stimulates motility and secretion while sympathetic nervous system inhibits this.

5
Q

What are some examples of reflexes?

A
Vagovagal reflex (vagus nerves) is a loop from vagal sensory afferents to CNS to vagal motor efferents. This includes gastric receptive relaxation, gastroileal reflex (clears intestine to make way for food).
Intestino-intestinal reflex inhibitory motor reflex initiated by intestinal distension (enlargement). Involves thoracolumbar neural pathways (sympathetic).
6
Q

What are the roles of gastrointestinal peptide hormones used to regulate GI function?

A

Gastrin - allows acid secretion, increases stomach motility and pepsinogen secretion.
Secretin - Inhibits acid secretion and stimulates bicarbonate and bile ejection from gallbladder.
Cholecystokinin - Inhibits acid secretion and stimulates secretion of pancreatic enzymes and ejection of bile from gallbladder, antagonist to gastrin.
Gastric inhibitory peptide - allows fatty acid metabolism, stimulates insulin secretion.