13.7 Physiology: Neural and hormonal control of GI function 1 Flashcards
What are Interstitial Cells of Cajal?
What do they do?
What are they connected by?
What are they dependent on?
- Modified smooth muscle cell
- ‘Pacemakers’ of the GI tract
- Gap junctions
- Largely independent
What are examples of mucosal enteroendocrine cells (EE) and what do they release (2)?
EC cells (serotonin) ECL cells (histamine)
What are different mediators contained in EE cells (4)?
CCK, secretin, somatostatin, GLP-1&2
EE cells often span the…..
Epithelium
What mediates movement in the upper GI tract?
What are 3 examples of its actions?
Vago-vagal reflex (swallowing, acid secretion, stomach/duodenal contractions)
What are intestino-intestinal reflexes mediated by?
Some, vagus. Others via dorsal root ganglia and spinal cord
Where do viscerofugal neurons project and what do they do?
From GI tract–> pre-vertebral sympathetic ganglia
Produce reflex inhibition if distention occurs
What does the cephalic phase of digestion involve? (4)
What controls it?
What % of gastric acid secretion does it account for?
- Salivation, gastric acid and pepsin secretion, receptive relaxation
- Vagus
- 30%
What cells secrete pepsinogen, acid, gastrin and somatostatin?
Pepsinogen: Chief
Acid: Parietal
Gastrin: G
Somatostatin: D
What route do gastrin and somatostatin take to reach parietal cells?
Via portal vein and liver
What 4 mediators interact to regulate acid secretion and from which cells?
ACh (enteric neurons)
Gastrin (G cells)
His (ECL)
Somatostatin (D cells)
What cells do somatostatin inhibit and what is it stimulated by?
Inhibits: parietal, G cells
Stimulated by: acid and gastrin
What is histamine inhibited by and what is it excited by?
Inhibited by: somatostatin
Excited by: ACh from enteric neurons
What is chronic failure of the oesophageal sphincter called?
GERD or GORD
Does distention activate? What are secreted?
Activates: enteric, vago-vagal reflexes
Secreted: acid and pepsin
