Flashcards in Lecture 15: Enteric Nervous System (Sanchez) Deck (26):
explain the 3 divisions of the ANS to the GI tract
1) sympathetic (via thoracolumbar divisions)
2) enteric (via submucous-myenteric plexuses)
3) parasympathetic (via cranio-sacral divisions)
where does the myenteric ganglion of the enteric nervous system reside?
between circular and longitudinal muscles of the GI tract
motor innervation of the myenteric plexus
circular and longitudinal muscles
secretomotor innervation of the myenteric plexus
Where do the projections of the myenteric plexus extend?
submucosal ganglia, enteric ganglia of gall bladder, sympathetic ganglia
major function of the submucous plexus
innervation of the submucous plexus
muscularis mucosa, intestinal endocrine cells, submucosal vasculature
3 types of sensory receptors
mechanoreceptors, chemoreceptors, and thermoreceptors
what do mechanoreceptors of the GI tract detect?
muscular stretch, villous distortion, mucosal motion
what do chemoreceptors of the GI tract detect?
acid, amino acids, lipid, glucose, osmolarity of meal
intrinsic primary afferent neurons
neurons that remain intrinsic and modulate GI activity at a local reflex level
extrinsic primary afferent neurons
neurons that project from the GI tract to the brainstem via the vagus n, or to the spinal cord via the dorsal root ganglion to initiate central modulatory responses
prominent peptides involved in afferent neural transmission
serotonin, substance P, and CGRP
Where do enteric motor neurons arise?
brainstem (for parasymp.) or spinal cord (for symp.)
Explain pathway of splanchnic nerve transmission
visceral sensory receptor --> primary afferent fiber --> dorsal root gangion --> synapses on sympathetic neuron --> symp. preganglionic fiber --> paravertebral ganglion --> prevertebral ganglion --> symp. postganglionic neuron
pathway of vagal n. transmission
afferent sensory --> nucleus tractus solitarius in medulla --> synapses on dorsal motor nucleus and nucleus ambiguus --> descending efferent motor nerves
primary inhibitory neurotransmitters in PARASYMPATHETIC enteric nervous system
VIP, nitric oxide
stimulatory neurotransmitters in parasympathetic enteric nervous system
substance P, Ach. Substance P causes contraction, Ach causes relaxation.
primary inhibitory NT in SYMPATHETIC enteric nervous system
Where do sympathetic enteric motor neurons synapse?
within paravertebral ganglia. (They are post-ganglionic fibers)
default state of circular muscle intrinsic primary afferent neurons?
relaxed. Activation via ascending excitatory reflex results in contraction proximally, and distal relaxation via descending inhibitory reflex to move ingesta through the GI tract
alteration in pain threshold; an extenuated pain reflex
when something that normally isn't painful becomes painful
general term for decreased motility in GI tract. Can be from inflammation, pain, etc.
general term for abdominal pain