Lecture 15: Enteric Nervous System (Sanchez)

Question 1

explain the 3 divisions of the ANS to the GI tract

Answer 1

1) sympathetic (via thoracolumbar divisions)
2) enteric (via submucous-myenteric plexuses)
3) parasympathetic (via cranio-sacral divisions)

Question 2

where does the myenteric ganglion of the enteric nervous system reside?

Answer 2

between circular and longitudinal muscles of the GI tract

Question 3

motor innervation of the myenteric plexus

Answer 3

circular and longitudinal muscles

Question 4

secretomotor innervation of the myenteric plexus

Answer 4

mucosa

Question 5

Where do the projections of the myenteric plexus extend?

Answer 5

submucosal ganglia, enteric ganglia of gall bladder, sympathetic ganglia

Question 6

major function of the submucous plexus

Answer 6

intestinal secretion

Question 7

innervation of the submucous plexus

Answer 7

muscularis mucosa, intestinal endocrine cells, submucosal vasculature

Question 8

3 types of sensory receptors

Answer 8

mechanoreceptors, chemoreceptors, and thermoreceptors

Question 9

what do mechanoreceptors of the GI tract detect?

Answer 9

muscular stretch, villous distortion, mucosal motion

Question 10

what do chemoreceptors of the GI tract detect?

Answer 10

acid, amino acids, lipid, glucose, osmolarity of meal

Question 11

intrinsic primary afferent neurons

Answer 11

neurons that remain intrinsic and modulate GI activity at a local reflex level

Question 12

extrinsic primary afferent neurons

Answer 12

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

Question 13

prominent peptides involved in afferent neural transmission

Answer 13

serotonin, substance P, and CGRP

Question 14

Where do enteric motor neurons arise?

Answer 14

brainstem (for parasymp.) or spinal cord (for symp.)

Question 15

Explain pathway of splanchnic nerve transmission

Answer 15

visceral sensory receptor –> primary afferent fiber –> dorsal root gangion –> synapses on sympathetic neuron –> symp. preganglionic fiber –> paravertebral ganglion –> prevertebral ganglion –> symp. postganglionic neuron

Question 16

pathway of vagal n. transmission

Answer 16

afferent sensory –> nucleus tractus solitarius in medulla –> synapses on dorsal motor nucleus and nucleus ambiguus –> descending efferent motor nerves

Question 17

primary inhibitory neurotransmitters in PARASYMPATHETIC enteric nervous system

Answer 17

VIP, nitric oxide

Question 18

stimulatory neurotransmitters in parasympathetic enteric nervous system

Answer 18

substance P, Ach. Substance P causes contraction, Ach causes relaxation.

Question 19

primary inhibitory NT in SYMPATHETIC enteric nervous system

Answer 19

NE

Question 20

Where do sympathetic enteric motor neurons synapse?

Answer 20

within paravertebral ganglia. (They are post-ganglionic fibers)

Question 21

default state of circular muscle intrinsic primary afferent neurons?

Answer 21

relaxed. Activation via ascending excitatory reflex results in contraction proximally, and distal relaxation via descending inhibitory reflex to move ingesta through the GI tract

Question 22

hypersensitivity

Answer 22

alteration in pain threshold; an extenuated pain reflex

Question 23

allodynia

Answer 23

when something that normally isn’t painful becomes painful

Question 24

ileus

Answer 24

general term for decreased motility in GI tract. Can be from inflammation, pain, etc.

Question 25

colic

Answer 25

general term for abdominal pain

Question 26

inflammation –> GI motility

Answer 26

decreases