GI: Neuromodulators

Question 1

Acetylcholine (Ach)

Answer 1

Source: Cholinergic Neurons (Parasympathetic mostly)

Actions: Contraction of smooth muscle in the walls and relaxation of sphincters. Increases salivary, gastric, and pancreatic secretions (Activates GI)

Question 2

Norepinephrine (NE)

Answer 2

Source: Adrenergic Neurons (Sympathetic)

Actions: Relaxation of smooth muscle walls and contraction of sphincters. Increases salivary secretion. (Inactivates GI) Helps control the blood supply to the gut.

Question 3

Vasoactive Intestinal Peptide (VIP)

Answer 3

Source: Neurons of mucosa and smooth muscle

Actions: Relaxation of smooth muscle, increase in intestinal and pancreatic secretion

Question 4

Gastrin-Releasing Peptide (GRP) or Bombesin

Answer 4

Source: Neurons of gastric mucosa

Action: Increases gastric secretion

Question 5

Enkephalins (opiates)

Answer 5

Source: Neurons of mucosa and smooth muscle

Action: Contraction of smooth muscle and decrease of intestinal secretion

Question 6

Neuropeptide Y

Answer 6

Source: Neurons of mucosa and smooth muscle

Action: Relaxation of smooth muscle and decrease of intestinal secretion.

Question 7

Substance P

Answer 7

Source: Co-secreted with Ach (parasympathetics0

Action: Contraction of smooth muscle and increase in salivary secretion.