Transcript Endocrine control of GI Function

Endocrine Control of
Gastrointestinal Function
Jack L. Leonard 2004
GI Hormones
Hormone
Action
Release site
Secretion stimulus
Peptides, AA
Distention
Vagal activity
Gastrin
Gastric acid secretion
Growth of oxyntic gland
mucosa
Antrum
CCK
Gall Bladder contraction
Pancreatic juice secretion
enzyme
bicarbonate
Pancreatic exocirne growth
Duodenum
Jejunum
Secretin
Pepsin secretion
Pancreatic juice secretion
enzymes
bicarbonate
Pancreatic exocirne growth
Duodenum
GIP
Insulin secretion
Gastric acid secretion
Duodenum
Jejunum
duodenum
Peptides, AA
Fatty acids>8C
Acid
Acid
fat
Glucose, AA
Fatty acids
Candidate Hormones
Peptide
Motilin
Pancreatic
polypeptide
Enteroglucagon
Action
Gastric and
duodenal motility
Pancreatic juice secretion
enzyme
bicarbonate
unknown
Release site
Secretion
stimulus
Duodenum
Jejunum
Unknown
Pancreas
Protein
Fat
Glucose
Ileum
Glucose
Fat
Neurocrines
Peptide
Action
Release site
VIP
Relaxes sphincters
Relaxes gut circular muscle
Stimulates intestinal secretion
Simulates pancreatic
secretion
Duodenum
Jejunum
Bombesin or GRP
Enkephalins
Stimulates gastrin secretion
Stimulates smooth muscle
contraction
Inhibits intestinal secretion
Gastric mucosa
Muscosa and
smooth muscle
of GI tract
The Three Phases of Acid Secretion
150
Volume Secreted
during first 2 hrs
100
25
Volume (ml/15 min)
total
cephalic
20
gastric
50
total
intestinal
cephalic
15
10
gastric
5
intestinal
1
Fed meat
2
Hours
3
4
Cephalic Phase
sight, smell
taste, chewing
swallowing
conditioned reflex
+
Bombesin
+
Vagal nucleus
-
Acetylcholine
+
- Somatostatin
G-cell
Somatostatin
cell
gastrin
+
Oxyntic
cell
H+
Gastric Phase
local
reflex
acetylcholine
Stomach
distention
Vagovagal
reflex
Protein
digestion
Peptides
Amino
acids
bombesin
gastrin
acetylcholine
H+
Intestinal Phase
Protein
Digestion
products
Intestinal
G Cell
Gastrin
Intestinal
Endocrine
Cell
Enterooxyntin
Absorbed amino acids
H+
Factors Regulating Acid Secretion
Factors Regulating Acid Secretion
Conditioned stimuli
Smell, taste
Chewing
Swallowing
hypoglycemia
Vagus nerve
Gastrin
G cell
H20 &
HCO3-
AcH
AcH
Acinar cells
Duct cells
Enzymes
Gastrin
Factors Regulating Acid Secretion (cont)
Vagus nerve
(vagovagal reflex)
Parietal cell
Fat
Protein
H+
E cells
CCK
Peptides + Amino acids
Fat
S cells
H+
Secretin H20 &
Duct
cells
HCO3-
AcH
AcH
Enzymes
Secretin
CCK
Acinar
cells
Pancreatic Enzyme Secretion
Pancreas
Post-Prandial
Pre-Prandial
Monitor peptide
Food Protein
Chymotrypsin
Trypsin
Small intestine
CCK
Gut – Insulin Secretion
Neural reflexes
Intestinal dose
40
Oral dose
Insulin (mU/ml
Insulin (mU/ml
100
50
20
0
1
20
min
0
40
4
min
8
10% glucose
100
100
0
0
10% glucose
5 min