Gastrointestinal Physiology COPY Flashcards
What are the two types of action potential involved in gastrointestinal motility?
Slow waves - produced by cells of Cajal. Resting membran potential -50mV
Spike potential - occur at -40mV due to calcium influx through the Ca-Na channels
What are the two types of contraction that may occur in the gastrointestinal tract?
What are the main components of the gastrointestinal nervous system, functions and their locations?
- The local nervous systems
a) Myenteric plexus (Auerbach’s plexus) = GI muscle contraction (muscularis), inhibition of sphincters (VIP)
b) Submucosal (Meissener’s plexus) = secretions and blood flow, contraction of submucosal muscle (submucosa) - Autonomic nervous system input
- Sensory neurons
- Direct feedback on the myenteric and submucosal NS as well as feedback to the CNS via the vagus nerve.
What may be vasoactive intestinal peptides role in relation to the myenteric plexus?
Autonomic control of the enteric nervous system
- What nerves give parasympathetic innervation to the GIT?
- What nerves give sympathetic innervation to the GIT?
a) Which neurotransmitter?
GIT Sensory Neurons
- Location of cell bodies
- Functions
- Inputs
- Dorsal root ganglion and enteric nervous system
What are the two types of movement in the GIT?
Segmental contractions
Peristalsis
Which cranial nerves are required for the swallowing reflex?
Vagus and glossopharyngeal.
WHere is the swallowing centre located?
Which cranial nerves are involved in the efferent (motor) control of swallowing?
Trigeminal, vagus, glossopharyngeal,
Describe the nervous innervation of the oesophagus
Efferent (sensory)
- Vagus nerve
Afferent (motor)
- vagus and glossopharyngeal - proximal 1/3
- vagus only - distal 1/3
What are the main factors that will stimulate the duodenum to inhibit gastric emptying?
- Distension of the duodenum
- Irritation of the duodenal mucosa
- Acidity in the chyme
- Osmolality of the chyme
- Nutrient content of the chyme (particularly fats)
Which locally produced hormones stimulate and inhibit gastric empting?
Stimulate
- Gastrin
Inhibit
- CCK (most potent)
- GIP
- Secretin
Gastroenteric reflex
Duodenal stretch results in inhibition of gastric motility
Explain:
1) Peristaltic rush
2) Mucosal movements
- Rapid peristalsis that occurs with SI irritaiton resulting in rapid clearance of the duodenum
- Control of small intestinal villous surface area by contraction of the muscularis mucosae.
Which hormons stimulate and inhibit peristalsis?
Increase
Decrease
- Gastrin
- CCK
- Insulin
- Motilin
- Serotonin
- GIP
- Secretin
What are the events that must occur to allow defecation to occur?
Intrinsic defecation reflex, initiated by the myenteric plexus, inreases peristalsis and relaxes the internal colonic sphincter. The parasympathetic nervous system must also add to the strength of this peristalsis and allow relaxation of the external sphincter.