7.3 Neural Functions of the Gut

Question 1

Neurocrines

Answer 1

• peptides that alter GI function.
• In the gut these trigger an increase in smooth muscle tone of the gut, thereby reducing GI motility.

Question 2

What are the transmitters that influence secretory and motor activity in the Gastrointestinal tract?

Answer 2

1. Peptide: VIP (vasoactive intestinal polypeptide)— Located: Gut mucosa and SM—— Action: Relaxation of gut SM.
2. Peptide: GRP: Gastrin-releasing peptide (Bombesin)—Located: Gastric mucosa—- Action: Increased Gastrin Release
3. Peptide: Enkephaline—— Located: Gut mucosa and SM—– Action: Increased SM tone

Question 3

VIP (Vasoactive intestinal Polypeptide)

Answer 3

promotes relaxation of smooth muscle associated with he gastrointestinal tract.

Question 4

GRP (Gastrin-releasing peptide (Bombesin)

Answer 4

triggers gastrin release from the G cells

Question 5

• Enkephalins

Answer 5

bind to opioid receptors and are involved in the control of nociception, pre pain sensation.

Question 6

Second Brain

Answer 6

-more neurons than spinal cord & can operate independently of the brain.
- provides sensory afferent information about Gi function

Question 7

What are the 2 main nerve plexus ?
(which is a cluster of neurons that receive and integrate input signals and then project output signals to other neurons or effector cells)

Answer 7

1. Myenteric (Auerbach’s plexus): these neurons are primarily motor in function, and they’re involve in GI motility.
2. Submucosal (Meissner’s Plexus): these neurons serve primarily a sensory function and are involved in local control of secretion and absorption, though they are involved in modulating the contraction of the muscularis mucosae.

Question 8

WHAT ARE THE 2 MAIN TYPES OF NEURAL CONTROL DELINATED BY THE SOURCE OF THE NEURONS CONDUCTING THESE IMPULSES.

Answer 8

1. Intrinsic Control - Enteric nervous system (control that resides within the GI tract and includes)
   - Myenteric (Auerbach’s) plexus
   - Submucosal (Meissner’s) plexus
2. 2. Extrinsic Control - Autonomic nervous system (refers to the autonomic neurons of the parasympathetic systems that are part of the peripheral nervous system.
      - Parasympathetic - mainly stimulates (ACh)
      - Sympathetic - mainly inhibits (NE)

Question 9

IPANs

Answer 9

are involved in initiating peristalsis and ensuring that contractions and relaxations are dynamic.

Question 10

True/False: The enteric nervous system operates independently of the brain

Answer 10

TRUE

Question 11

True/False : Both components of the autonomic nervous system synapse with the Auerbach’s & Meissner plexuses.

Answer 11

TRUE

Question 12

Which kind of receptors do neurotransmitters released from preganglionic parasympathetic communicate?

Answer 12

Nicotinic

Question 13

What locations do sensory neurons from the gut epithelium synapse

Answer 13

• Auerbach’s plexus
• Meissner’s plexus
• submucosa
• muscularis externa