Bsf Exam 5: Enteric Nervous System

Front 1

Describe the organization of ENS, from innermost to outermost

Back 1

lumen
mucosa
mucosal plexus
muscularis mucosa
submucosa
meissner's plexus
circular muscularis externa
myenteric plexis
longitudinal muscularis externa

Front 2

T/F
The enteric system contains as many cells as the spinal cord

Back 2

TRUE

Front 3

T/F
When isolated from CNS, ENS may still coordinate basic reflexive function of secretion, absorption, & mixing & movement of luminal contents

Back 3

TRUE

Front 4

What are the two neuronal networks of the ENS?

Back 4

1. Myenteric (Auerbach's Plexus)

2. Submucosal (Meissner's Plexus)

Front 5

The ENS recieves input from (parasympathetic/sympathetic) neurons

Back 5

BOTH parasympathetic & sympathetic

Front 6

(myenteric/submucosal) extends through the entire GI tract

Back 6

myenteric

Front 7

(myenteric/submucosal) is limited to the small and large intestine

Back 7

submucosal

Front 8

Plexus organized into ganglia contain (one/many) cells.

___________ interconnect ganglia & plexus

Back 8

many (btwn 5-10 up to hundreds)

nerve bundles

Front 9

Neuronal cells w/i the ENS have ______and _________ axons, and contain _______ of the CNS (not periphery)


There are ___ neuronal cell types w/i ENS

Back 9

fine and umyelinated axons

glia

15

Front 10

Sensory neurons of the ENS respond to 2 kinds of stimuli:

Back 10

mechanoreceptors

chemoreceptors

Front 11

What are the 4 mechanisms of sensory neuron projection?

Back 11

1. Intrinsic confined to ENS (IPAN: intrinsic primary afferent neurons)
2. Projection via vagus to brainstem (vagal primary afferents)
3. Nociceptive projection to sympathetic ganglion (intestinofugal neurons)
4. Projection via dorsal root to spinal cord (spinal primary afferent)

Front 12

What do intermediary epithelial cells secrete in response to luminal pH, inorganic acids, short chain fatty acids, toxins, ect?

Back 12

serotonin
(5-HT)

Front 13

What does serotonin do?

Back 13

activates sensory cells

*many sensory cells respond to multiple stimul types = polymodal

Front 14

Excitatory motor neurons act on smooth muscle via intermediary cells known as, ________________________

Back 14

interstitial cells of Cajal (ICC)

Front 15

Interstitial cells of Cajal (ICC) are non-neuronal, pacemaker cells, that are electrically coupled to what?

Back 15

unitary smooth muscle units

Front 16

What are the excitatory transmitters that act via metabotropic receptors?

What else is released?

Back 16

Ach & tachykinin


Opoids & GABA

Front 17

Transmitters act on autoreceptors to negatively feedback on motornuerons, what is the result of this?

Back 17

reduced transmission

(via this pathway that opiates induce constipation)

Front 18

Inhibitory motor neurons also act on smooth muscle via ICC. What are the inhibitory transmitters?

Back 18

NO, ATP, vasoactive intestinal peptide & pituitary adenyl cyclase activating peptide

Front 19

_______________oscillation is propagated into smooth muscles, giving rise to passive oscillations in the muscle called, ___________

Back 19

ICC Vm oscillation

slow waves

Front 20

T/F
Enteric input changes frequency & amplitude of slow waves

Back 20

FALSE
enteric input does NOT change frequency
(only amplitude)

Front 21

If slow waves are ____________ no muscle contraction occurs

Back 21

subthreshold

Front 22

Slow waves propagate in the _____________ direction.

What does this result in?

Back 22

rostro-caudal direction

resulting in a delay from one depolarized zone to the next

Front 23

Enteric input shifts ___________ and consequently _____ oscillations in muscle

Back 23

potential and consequently Vm oscillations

(**does not shift pacemaker freq of ICC)

Front 24

Secretions in GI & exocrine glands depend on what?

Back 24

water from blood

Front 25

Neurons innervate smooth muscle of arteriole & crypts of Lieberkuhn, they induce __________ by the crypts and by osmosis induce ___________

Back 25

Cl- secretion by crypts

osmosis induce water excretion

Front 26

In stomach, action of _________is on parietal cell to do what?

Back 26

secretomotor vasodilators

induce gastric acid secretion

Front 27

What is the secretomotor response to noxious stimulants?

Back 27

-stimulus depolarizes epithelial cell resulting in serotonin & prostaglandin synthesis & release
-these activate IPAN & induce Cl- secretion
-results in diarrhea & massive fluid loss

Front 28

How does Cholera toxin lead to death?

Back 28

permanently activates IPAN & induces Cl- sectretion via adenyl cyclase, leads to diarrhea & massive fluid loss which eventually cause dehydration & death

Front 29

How does the enteric system regulate gastrin release?


what does gastrin do?

Back 29

-G cells in gastric antrum recieve parasympathetic input (food smell, etc) from enteric neurons via vagus nerve, GRP (gastrin-releasing peptide) induces gastrin release.

-gastrin induces acid secretion by parietal cells
(*Pavlov)

Front 30

What types of interneurons are w/i the ENS?

Back 30

-ascending
-descending
-interconnecting (btwn myenteric & submucosal)

Front 31

How do preganglionic cells from the parasympathetic reach ENS?

How do postganglionic cells reach ENS?

Back 31

preganglionic project via vagus & pelvic nerve (from sacral spinal cord) into enteric

postganglionic are w/i ENS

Front 32

How do the cholinergic parasympathetic cells affect ENS?

Back 32

increase vasodilation, secretory activity, and peristaltic movement

Front 33

Describe GI motility

Back 33

-propulsion (peristalsis) moves content caudally
-segmental contraction mixes content w/ digestive enzymes
-migrating motor complexes (MCC) of small intestine clean lumen & shed epithelial cells btwn meals
-opening & closing of sphincters
*enteric involved in all

Front 34

Describe propulsive movement

Back 34

circular muscle above bolus contract & circular muscle below relax, pushing bolus down from oral cavity toward anus

Front 35

Steps of Propulsive movement

Back 35

1. IPAN responds to distension, activating chain of ascending & descending interneurons
2. Ascending contact exitatory motorneurons that induce contraction of circular muscle via ICC
2. Descending contact inhibitory motorneurons that induce relaxation of circular muscle via ICC
3. Excitation & inhibition impacts amplitude with changes contraction level by altering # of action potentials

Front 36

T/F
Since the upper 1/3 of esophagus is surrounded by skeletal muscle, enteric neurons do not modulate

Back 36

FALSE

enteric neurons DO form synapses on motor end plate & modulate synaptic activty in upper esophagus!

Front 37

Distension due to bolus & chemical stimulus also induces local _________

How does this occur?

Back 37

local secretomotor activity

-stimulated IPAN activates descending interneurons
-interneurons activate secretomotor neurons
-secretomotor neurons induce vasodilation & Cl- secretion into lumen
-Cl- secretion induces water movement into lumen

Front 38

When pyloric sphincter is closed, gastric peristalsis results in ________ via ______________

What is gastric peristalsis due to in this case?

Back 38

churning
via migrating motor compex (MMC)

due to ICC
(enteric excitatory motor neurons not essential)

Front 39

All sphincter w/i the GI tract are controlled by the ENS except for which 2?

Back 39

esophageal & external rectal sphincters
(skeletal muscles)

*esophageal control mostly vagal
*external rectal somatic

Front 40

What enterically controlled sphincter controls the passage of bile from gallbladder & pancreas into deodenum?

Back 40

sphincter of Oddi

Front 41

Describe the 3 actions involved in the rectosphincteric reflex?

Back 41

1. fecal matter stretches/stimulates internal rectal sphincter to open (ENS)
2. opening of internal sphincter leads to increased motor activty from (PNS, sacral spinal cord neurons)
3. external rectal sphincter can be opened voluntarily (CNS)

Front 42

Short reflexes, such as the entero-enteric reflex occur how?

Back 42

one caudal segment of intestine can modulate activity in a more rostal segment (LOCAL) via ascending interneurons

Front 43

Long reflexes, such as the enterogastric reflex occur how?

Back 43

emptying of stomach into duodenum is regulated by 1. a long distance ascending interneuron (DISTANT) & 2. a sympathetic duodenum-paravertebral ganglion stomach pathway

Front 44

How is the enterogastric (long) reflex induced (3 ways)?

Back 44

1. distention of duodenum
2. pH in duodenal chyme
3. osmolarity of duodenal chyme
4. irritants in duodenum
5. presence of certain digestive breakdown enzymes in duodenal chyme

Front 45

General motor activity of the intestine is also regulated by ____________ input

Back 45

sympathetic input

Front 46

How does the sympathetic system affect the enteric system?

Back 46

-postganglionic cells project from paravertebral or prevertebral
-noradrenergic
-inhibit secretion & motility
-vasoconstriction
-sensory neurons (intestinofugal) project to prevertebral ganglion to modulate secretion & motility inhibition