1. GUT PHYSIOLOGY Introduction Dr. Jack Grider Rm 12-004 Sanger Hall
2009

2. Digestive Processes

3. ANATOMY red denotes a sphincter Salivary Glands Liver Pancreas
duodenum, jejunum, ileum
Rectum
Pancreas
red denotes a sphincter

4. SPHINCTERS

5. Summary of Gut Physiology

6. Layers of the Gut Wall

7. Fourth mechanism: autocrine
Control Mechanisms
Fourth mechanism: autocrine

8. Neural Control Mechanisms
Hormone/Paracrine agent

9. CNS Control
- Extrinsic
- Autonomic N.S.
ANS

10. Extrinsic Control Mechanisms P.S.N.S. is excitatory

11. Extrinsic/Autonomic S.N.S. is inhibitory

12. Sympathetic Nervous System Presynaptic Inhibition

13. Sympathetic Nervous System

14. Afferent/Sensory Neurons
Extrinsic Primary
Afferent

15. REFLEXES THAT CONTROL GUT FUNCTION Long Arc Reflexes: PSNS

16. Extrinsic/Autonomic N.S. Long Arc Reflexes: PSNS
Vago-Vagal Reflex
CNS

17. Extrinsic/Autonomic N.S. Long Arc Reflexes: SNS 3 pathways

18. Extrinsic/Autonomic N. S
Extrinsic/Autonomic N.S. Long Arc Reflexes: SNS Intestino-Intestinal reflex

19. Intrinsic/Enteric N.S.
The “little brain” or
“mini-brain”

20. Intrinsic/Enteric N.S.

21. Intrinsic/Enteric N.S. Short Arc Reflexes

22. Intrinsic/Enteric N.S. Many neuronal types IPANs (sensory)
Intestinofugal
Interneurons & motor neurons
Transmitters: Ach/ TKs (~45%)
VIP/NO (~25%)
Enk, GRP, SSt,. …….

23. Hormonal Control Mechanisms
Blood vessel

24. Hormonal Control Mechanisms
All gut hormones are polypeptides
All are amidated at C-terminal end
Importance varies: proximal vs. distal
Criteria
Candidates vs. putative hormones

25. Hormonal Control Mechanism Gastrin
Multiple forms: G-17, G-14, G-34 etc.
Tyr-12 can be sulfated (equal amounts)
C-terminal end
Synthesized in G-cells of terminal antrum, minor amounts in duodenum.
Released by: protein digestion products
antral distension(direct, vagal & ENS)
vagal stimulation (cephalic phase)

26. Hormonal Control Mechanism Gastrin
Physiological Action: Gastric HCl secretion
growth of mucosa (trophic)
stimulation of gastric motility (?)
Negative feedback regulates release
Pharmacological effects (impt. sulfation)
Zollinger-Ellison Syndrome

27. Hormonal Control Mechanism Cholecystokinin
Multiple forms: CCK-8, CCK-33, CCK-39, CCK-58 etc.
Sulfated in 7th AA from C-terminal end.
C-terminal end
Synthesized in I cells of duodenum (CCK-8, -4 in neurons of ENS and CNS)
Released by:protein digestion products monoglycerides/FFA, HCl (minor)

28. Hormonal Control Mechanism Cholecystokinin
Physiological Action:
pancreatic enzyme secretion
gallbladder contraction
mucosal growth & pancreatic growth (trophic)
inhibit gastric emptying in high conc.
Pharmacological Action

29. Hormonal Control Mechanism Secretin
Single form: 27 AA
Structure similar to GIP, VIP, Glucagon
Released from S cell in proximal small intestine.
Released by: HCl monglyceride/FFA (minor)

30. Hormonal Control Mechanism Secretin
Physiological Action
stimulate bicarbonate ion secretion from duodenal glands, duct cells of biliary and pancreatic system,
growth of pancreatic tissue
inhibits acid secretion and gastric emptying.

31. Hormonal Control Mechanism Glucose-dependent Insulinotrophic Peptide (GIP)
Singular form: 42 AA
Structure similar to Secretin, VIP, Glucagon
Synthesized in K cells of proximal small intestine
Released by: nutrients in proximal small intestine.
Physiological action: Stimulate insulin secretion by the pancreas
inhibit gastric acid secretion (?)

32. Hormonal Control Mechanism Candidate Hormones
Enteroglucagon
Pancreatic polypeptide family (PP, PYY, NPY)
Somatostatin
Motilin & Ghrelin
Many more ...

33. Paracrine Control Mechanisms
Local control
Somatostatin, Histamine, GRP