Lecture 19: Viscerosensory Processing in the NTS Flashcards

1
Q

What is the solitary tract?

A

the VIIth, VIIIth and Xth cranial nerves

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2
Q

What is an output of the solitary tract?

A

the NTS

this is where cranial viscerosensory afferents terminate

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3
Q

What is the path of cranial viscerosensory afferent neurons from the periphery to the brain?

A

periphery -> vagus nerve -> Xth cranial nerve -> solitary tract -> NTS

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4
Q

What does injection of tracing dyes into ganglia known to contain the cell bodies of these neurons (such as the nodose) reveal?

A

that their terminal fields are in the NTS

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5
Q

The presence of which protein suggests that they are forming synapses with NTS neurons?

A

synaptophysin

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6
Q

Where do cranial visceral sensory neurons synapse?

A

at second order neuron soma

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7
Q

What do visceral signals evoke?

A

glutamate release at the ST-NTS synapse

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8
Q

What is the process of synchronous neurotransmitter release?

A

membrane depolarisation -> voltage gated sodium channels -> voltage activated calcium channels -> neurotransmitter release

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9
Q

What is the percentage of NTS neurons that receive one, two and three inputs?

A

65%
20%
15%

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10
Q

What is the nature of the solitary tract input to NTS?

A

a relatively sparse excitatory network, where one primary afferent dominates the information pathway

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11
Q

What do cranial visceral sensory neurons input to?

A

dedicated second order neurons

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12
Q

What are characteristics of myelinated A-fibers?

A

active at resting blood pressure
fine-tune autonomic function
myelinated

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13
Q

What are characteristics of unmyelinated C-fibers?

A

activated at elevated blood pressure

TRPV1

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14
Q

What does asynchronous release extend?

A

the postsynaptic excitatory period

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15
Q

Which class of neuron expresses TRPV1 receptors?

A

C-fibers

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16
Q

Which class of neuron expressing TRPV1 exhibits asynchronous glutamate release?

A

C-fibers

17
Q

Capsaicin inhibits the activation of second order NTS neurons as evoked by electrical activation of the solitary tract. By what mechanism does this occur?

A

depolarisation block in the presynaptic neuron

18
Q

What are the two major evoked modes of neurotransmitter release?

A

synchronous and asynchronous

19
Q

Where is TRPV1 expressed? What do they release?

A

at C-fiber cranial visceral afferents and release additional glutamate via asynchronous release