Enteric Nervous System

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Who defined the three peripheral nervous systems
langley, 1921
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What is the ENS
morphologically distinct from the other two - because it has more than two neurons in the efferent chain from the CNS, and complex reflex pathways in the gut wall
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The two major intrinsic networks of ganglia in the ENS
outer myenteric plexi, and inner submucosal plexi
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What is the outer myenteric plexi?
Auerbach's plexus - provides motor innervation to both layers of the muscular layer of the gut
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What is the inner submucosal plexi
meissners plexus - mainly controls mucosal function and mucosal blood flow.
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Where are these layers located
Myenteric plexi - between the inner and outer layers of the muscularis externa. Submucosal - in the submucosa between the mucosa and the muscularis propria
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Which one has more neuronal types?
The outer myenteric plexi
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How many neurons in the ENS
10^8
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Dogeil classification of enteric nerves
dogiel type 1,2 and 3, and stach type IV.
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Which one is most common?
Proportions vary within GI areas and between species. 80% of SMP neurons can be stach type.
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Describe dogiel type 1 (d, a, m)
Flattened with 4-20 dendrites, 1 long axon. Motor
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Describe dogiel type 2
angular, star shaped. with 3-10 longer dendrites, multiaxonal. Sensory
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Describe dogiel type 3
Oval cell bodies, 2-10 dendrites that end within ganglion, no single function
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What types do you find in the MP
1,2, AND 3 but never type 4
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What types do you find in the SMP
2, 3, 4 BUT NEVER TYPE 1
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What are type 1 neurons like?
Synaptic neurons, similar to those seen in the ANS - low resting potential, fast ACh epsps
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Dogiel type 2 are what type
after hyperpolarising neurons. only found in the END. They are IPANS
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What does IPAN stand for
intrinsic primary afferent neurons
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What are type 3 like
no ap or AH - but have fast N synaptic inputs.
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Stach type are like -
low excitability. No AH but do exhibit TTX-sensitive single spikes
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Distribution patterns suggest
functional roles
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Where do type 2 project to
Cell bodies in the SM, project to the MP,
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What excitatory small molecule neurotranmitters are prominent in the ENS
ACh, 5H-T, glutamate, ATP
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excitatory neuropeptides
SP and related neurokinins NKA and NKB
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Prominent inhibitory small molecule neurotransmitters;
gaba, no
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Inhibitory neuropeptides;
vip, pacap, NPY, Dynorphin,. Somatostatin
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What is neuropeptide release in the ENS like?
The majority of ENS neurons express several neuropeptides
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Five functional types of intrinsic enteric nerves
motor, interneurons, sensory, secretomotor, and vasodialators
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Where are the cell bodies of sensory neurons?
MP or SMP. release SP, NKA and CGRP
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FOUR afferent neurons in the ENS
conventional with cell bodies in the DRG, conventional with cell bodies in vagal sensory ganglia, IPANS, intestinofugal
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what do intestinofugal neurons do?
convey singals to sympathetic prevertebral ganglia. involved in entero-enteric reflexes.
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Card 2

Front

What is the ENS

Back

morphologically distinct from the other two - because it has more than two neurons in the efferent chain from the CNS, and complex reflex pathways in the gut wall

Card 3

Front

The two major intrinsic networks of ganglia in the ENS

Back

Preview of the front of card 3

Card 4

Front

What is the outer myenteric plexi?

Back

Preview of the front of card 4

Card 5

Front

What is the inner submucosal plexi

Back

Preview of the front of card 5
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