GI Physiology: Hormones Flashcards
What is the overall purpose of Gastrin and its pathway of activity?
Gastrin is the stimulator of the Gastric mucosa. Responds to food.
Peptides/Distension of stomach/GRP –> Secretion of Gastrin from G cells in antrum –> (1)H+ release from parietal cells/(2) growth of gastric mucosa
What factors inhibit Gastrin secretion?
Somatostatin
Decreased pH
What is the overall purpose of CCK and its pathway of activity?
CCK stimulates the digestion of fats and controls the gallbladder.
Monoglycerides, FAs, AAs –> secretion of CCK from I cells in duodenoum and Jejunum –> Effects (see table)
Effects:
- Contraction of Gallbladder + relaxation of sphincter of oddi
- Secretion of pancreatic enzymes (amylase, lipase, proteases, and HCO3-)
- Growth of pancreas + Gallbladder
- Decreased gastric emptying time
What is the overall purpose and physiologic pathway for Secretin?
Secretin increases the pH in the duodenum in response to acidity.
high H+, and FAs in duodenum –> Secretion of secretin from S cells in duodenum –> Increased pancreatic HCO3- release, increased biliary HCO3 secretion, decreased gastrin effects.
What is the overall purpose and physiologic pathway for Motilin?
Motilin stimulates gut motility
High fat and/or acid, Neural input (MI) –> secretion of motilin from duodenum and jejunum –> Increased gastric + intestinal motility
What is the overall purpose and phsyiologic pathway for GIP?
Improves insulin response to and ingested meal
AA, FAs, Glucose –> secretion of GIP from K cells in Duodenum/Jejunum –> increased insulin secretion and decreased gastric H+ secretion.
What is the overall purpose and physiologic pathway for Somatostatin?
Inhibitor of all things hormone
Low pH –> secretion of somatostatin from GI mucosa (MI) and pancreatic islets –> Decreased GI hormones and H+ secretion.
What inhibits somatostatin release?
Vagal stimulation
What is the only hormone that is stimulated by all 3 nutrient types?
GIP
What is the overall purpose and physiologic pathway for histamine?
In the GI tract histamine stimulates H+ secretion
Gastrin –> release of histamine from ECL cells –> increased Gastric pH secretion by parietal cells
What is the primary function of Vasoactive intestinal peptide (VIP)?
Neurocrine:
Relaxation of muscle wall via NO. Increases all secretions
What is the function of Gastrin related Peptide (GRP aka Bombesin)?
Neurocrine:
Increased Gastric secretion
Secreted from vagal nerves
What are the functions of Enkephalins?
Neurocrine: opiates
Increased contraction of smooth muscle
Decreased intestinal secretion
What are the functions of Neuropeptide Y?
Neurocrine:
Relaxation of smooth muscle
Decreased intestinal secretion
What are the functions of substance P?
Neurocrine: co-secreted with Ach
Contraction of muscle
increased secretion of saliva
