Session 2 Lecture 1 Flashcards
What are the different control mechanisms of the gut?
Autonomic nervous system
Enteric nervous system
Hormones and paracrine substances
Briefly describe the autonomic nervous system
- Cell bodies reside in the CNS
- Preganglionic fibre synapse with an autonomic ganglia outside the CNS
- Postganglionic fibre synapse on peripheral effector organs
What two types of neurones are involved in each pathway in the autonomic nervous system?
Preganglioic and postganglionic
What substance do all preganglioic fibres release?
Acetylcholine
What substances do all post ganglionic fibres release?
Acetylcholine, neuropeptides or norepinephrine
Describe the preganglionic and postganglionic fibres of the parasympathetic nervous system
Long preganglioic and short postganglionic
Describe the pathway of sympathetic nerves?
Pass through paravertebral sympathetic trunk without synapsing. For abdominopelvic presynaptic splanchnic nerves. These splanchnic nerves synapse with prevertebral ganglia.
What is the function of the parasympathetic nervous system in the GI system?
Innervates smooth muscle/endocrine and secretory cells
What is the enteric nervous system?
It is one of the divisions of the nervous system that can operate completely independently (second brain)
What are the two main plexuses of the enteric nervous system?
Submucosal (meissner’s)
Myenteric (Auerbach’s)
Where submucosal (meissner’s) plexus found?
Submucosa
Where is the myenteric (auerbach’s) plexus found?
In between the circular and longitudinal muscle
What is the submucosal (meissner’s) plexus function?
Secretions and blood flow
What is the myenteric (auerbach’s) plexus function?
Motility
What are the two broad categories of gastrointestinal hormones?
Gastric family and secretin family
What are the two hormones that are part of the gastric family of GI hormones?
Gastrin and cholecystokinin (CCK)
What is the function of CCK)
Increases pancreatic/gallbladder secretions
- Stimulated by fat and protein
- Gall bladder contracts
- Pancreas stimulated
What is the main function of gastrin?
Increases gastric acid secretion
What are the different hormones in the secretin family of the GI hormones
Secretin and gastric inhibitory polypeptide (GIP)
What is the function of secretin?
- Stimulated by H+ and fatty acids
- Increases HCO3 from pancreas/gallbladder
- Decreases gastric acid secretion
What is the function of GIP?
- Cells in the duodenum and jejunum
- Stimulated by sugars, amino acids and fatty acids
- Increases insulin
- Decreased gastric acid secretions
