GI Innervation Flashcards
How do GI neurons release their neurotransmitters?
Neurotransmitters are released from varicosities along the length of the axon
Do neurons make “true synapses” on GI smooth muscle fibers?
No
Where is the myenteric plexus located?
In between the circular and longitudinal muscle (remember: “my-“ means muscle)
Where is the submucosal plexus located?
In between the submucosal layer and the circular muscle
What is an alternative name for the submucosal plexus?
Meissner’s plexus
Where is the enteric nervous system “wholly contained”?
Within the myenteric and submucosal plexuses, in the wall of the GI tract
The intrinsic component of the ANS is also called the…
Enteric nervous system (ENS)
The extrinsic component of the autonomic nervous system can also be thought of as…
The sympathetic and parasympathetic nervous systems
Parasympathetic innervation of the gastrointestinal tract is supplied by which two nerves?
- Vagus nerve (CN X)
2. Pelvic nerve
What GI structures receive parasympathetic innervation from the vagus nerve?
The upper GI tract: striated muscle of the upper 1/3 of the esophagus, wall of the stomach, small intestine, and the ascending colon
Which gastrointestinal structures receive parasympathetic innervation via the pelvic nerve?
The lower GI tract: striated muscle of the external anal canal and the walls of the transverse, descending and sigmoid colon
Describe the preganglionic fibers of the parasympathetic nervous system.
Long, synapse in or near the target organs
What are the two classifications for postganglionic neurons of the parasympathetic nervous system?
Cholinergic neurons (release ACh) Peptidergic neurons (release substance P, VIP and unknown neuropeptides)
Describe a vasovagal reflex.
Reflexes where both the afferent an efferent limb are contained in the vagus nerve.
Describe the preganglionic fibers of the sympathetic nervous system that innervate the GI tract.
Short, and synapse outside of the gastrointestinal tract.
What are the four sympathetic chain ganglia that serve the gastrointestinal tract?
- Celiac
- Superior mesenteric
- Inferior mesenteric
- Hypogastric
Are postganglionic nerve fibers of the sympathetic nervous system adrenergic or cholinergic?
Adrenergic, they release norepinephrine
If a patient loss all extrinsic (parasympathetic and sympathetic) innervation of the gastrointestinal tract, what would happen to the GI functions?
Gastrointestinal function would be maintained because the enteric nervous system (ENS) can direct all GI functions.
The ganglia in the myenteric and submucosal plexus receive sensory information directly from what 4 places?
- Mechanoreceptors
- Chemoreceptors
- Parasympathetic nervous system
- Sympathetic nervous system
The ganglia in the myenteric and submucosal plexuses send motor innervation directly to what 3 structures?
- Smooth muscle cells
- Secretory cells
- Endocrine cells
