Control of gut Flashcards
What are the methods of control of the gut?
Neural control
Hormonal control
Paracrine control
What is the neural control of the gut?
Autonomic nervous system control
Enteric nervous system control
What overall effect does sympathetic innervation have on the gut?
Inhibits the functions of the GI tract
How does the sympathetic nervous system inhibit the functions of the gut?
Causes vasoconstriction of blood vessels, reducing blood flow to the gut
Decreases secretions from glands
What neurotransmitters do the parasympathetic post-ganglionic nerve fibres release?
Acetylcholine
Gastrin releasing peptide
Vaso inhibitory peptide
What overall effect does parasympathetic innervation have on the gut?
Stimulates the functions of the GI tract
How does the parasympathetic nervous system stimulate the functions of the gut?
Increases motility of the gut
Increases secretions from glands
What are the parts of the enteric nervous system?
Submucosal plexus
Myenteric plexus
Where is the submucosal plexus located?
In the submucosa
Where is the myenteric plexus located?
Between the inner circulator layer and the outer longitdinal layer of the muscularis externae
How far along the GI tract does the enteric nervous system extend?
Along the whole GI tract
from the oeophagus to anus
What does the submucosal plexus control?
Secretions from epithelial cels
Local blood flow
What does the myenteric plexus control?
Motility
What is the relation between the autonomic and enteric nervous systems controlling the gut?
They are connected to each other
communicate with each other
What are the two families of hormones in the GI tract? What are the hormones in each family?
Gastrin
- gastrin
- cholecystokinin
Secretin
- secretin
- gastric inhibitory peptide
What types of cells produce hormones in the GI tract?
G cells
I cells
S cells
K cells
What hormone do G cells produce?
Gastrin
What hormone do I cells produce?
Cholecystokinin
What hormone do S cells produce?
Secretin
What hormone do K cells produce?
Gastric inhibitory peptide
How do hormones produced in the GI tract reach their target cells?
Diffuse into the blood
pass through the portal circulation
pass through the systemic circulation
diffuse into target tissue
even though target tissue is close to where they were initially produced
What is the function of gastrin?
Stimulates hydrochloric acid secretion from parietal cells of stomach
What is the function of cholecystokinin?
Stimulates release of enzymes from pancreas
Stimulates gall bladder to contract
Relaxes sphincter of Oddi
What is the function of secretin?
Stimulates increase in bicarbonate ion secretions from pancreas
Inhibits release of hydrochloric acid from parietal cells
What is the function of gastric inhibitory polypeptide?
Stimulates release of insulin from pancreas
Inhibits release of hydrochloric acid from parietal cells
What are the paracrine substances of the GI tract?
Somatostatin
Histamine
What type of cell produces somatostatin?
D cells
What type of cell produces histamine?
Enterochromaffin cells
How do paracrine substances reach their target tissue?
Diffuse across short distance
to target cell which is nearby
What is the function of somatostatin?
Inhibit secretion of gastrin from G cells
What is the function of histamine?
Stimulate release of hydrochloride acid from parietal cells
