C: Ascending sensory pathways 2

Question 1

Where are cranial nerve nuclei located?

Answer 1

Within the brainstem

Question 2

The trigeminal nerve is a major carrier of sensory info from where?

Answer 2

1) Face
2) Nose
3) Scalp
4) Dura

Question 3

The facial nerve carries general sensory info from where?

Answer 3

The external ear

Question 4

The glossopharyngeal nerve carries general sensory info from where?

Answer 4

1) Posterior 1/3 of tongue
2) Pharynx
3) Middle ear

Question 5

The vagus nerve carries general sensory info from where?

Answer 5

1) Auditory canal
2) Larynx
3) Pharynx
4) Oesophagus

Question 6

General sensory info from the head is carried in which central pathway?

Answer 6

Trigeminal sensory pathway

Question 7

Sensory fibres from the cranial nerves in the trigeminal sensory pathway run within which nucleus in the brain stem?

Answer 7

Trigeminal nucleus

Question 8

What 3 parts can the trigeminal nucleus be divided into?

Answer 8

Mesencephalic nucleus (extends into midbrain)
Pontine/chief sensory nucleus (bulbous part in pons)
Spinal nucleus (extends down into medulla towards spinal cord)

Question 9

Where does the motor nuclei of the trigeminal lie in relation to the sensory nuclei?

Answer 9

Motor nuclei is medial to the sensory nuclei

Question 10

How many trigeminal sensory nuclei are there within the brainstem?

Answer 10

2 - one on each side

Question 11

Somaesthetic inputs from the trigeminal sensory nucleus travel to which region of the post central gyrus?

Answer 11

Inferior post central gyrus mainly

Question 12

Pain and temperature info from the face travels to what part of the trigeminal nucleus?

Answer 12

Caudal part of the spinal nucleus

Question 13

Simple touch and pressure from the face travels to what part of the trigeminal nucleus?

Answer 13

Rostral part of the spinal nucleus

Question 14

Where are the cell bodies of the primary neurones in the trigeminal sensory pathway located?

Answer 14

In ganglia outside of the brainstem

eg. primary cell bodies of CNV in trigeminal ganglion, CN7,9,10 all have their own ganglion

Question 15

Where are the cell bodies of the secondary neurones in the trigeminal sensory pathways located?

Answer 15

(generally) in the trigeminal nucleus within the brainstem

Question 16

Pain and temperature info from the face is carried by what kind of nerve fibre?

Answer 16

Thin, slow fibre

Question 17

Do primary neurones in the TSP (trigeminal sensory pathway) enter the ipsilateral or contralateral trigeminal nucleus?

Answer 17

Ipsilateral

Question 18

Which neurone in the TSP crosses the midline?

Answer 18

The secondary neurone

Question 19

What would be the course of neurones carrying pain and temperature info from the face?

Answer 19

For example, carried by the trigeminal nerve:

1) Cell body of primary neurone in the trigeminal ganglion
2) Primary axon enters brain stem and travels caudally in the spinal tract of the trigeminal (which is quite superficial)
3) Enters the trigeminal nucleus at the caudal end and where it synapses with the secondary neurone
4) Secondary axon crosses the midline and ascends in the trigeminothalamic tract (lies deep within the brainstem) to the thalamus

Question 20

What would be the course of a neurone carrying touch and pressure information from the face?

Answer 20

In the case of the face info is carried in trigeminal nerve

1) Primary cell body in trigeminal ganglion
2) Primary axon enters brainstem and travels caudally in the spinal tract of trigeminal but enters the spinal nucleus more rostrally than a fibre carrying pain and temp info
3) Primary and secondary neurones synapse in the spinal nucleus
4) Secondary axon crosses the midline and ascends to thalamus in trigeminothalamic tract

Question 21

What would be the consequence of a lesion affecting the superficial lateral medulla - in terms of sensation from the face and sensation from the body?

Answer 21

1) Loss of pain, temp, touch and pressure on ipisilateral side of face (primary axons carrying this info descend on in the spinal tract which lies superficially in the lateral medulla)
2) Loss of pain, temp, touch and pressure on the contralateral side of the body - spinal lemniscus (spinothalamic tract in medulla) lies superficially in the medulla which carries this info from the lateral side of the body

Question 22

Neurones carrying discriminative touch information travel to which part of the trigeminal nucleus?

Answer 22

Pontine nucleus

Question 23

Neurones carrying proprioception travel to which part of the trigeminal nucleus?

Answer 23

Mesencephalic nucleus

Question 24

How does the pathway of neurones carrying proprioception info from the face differ slightly to the pathway of other neurones in the trigeminal sensory pathway in terms of cell body position?

Answer 24

Primary neuron cell bodies (first order cell bodies) don’t lie in a peripheral ganglion - they lie within the mesencephalic nucleus
Secondary cell bodies lie just outside the trigeminal nucleus thus the primary and secondary axons synapse outside of the trigeminal nucleus

Question 25

What would be the course of neurones carrying discriminative touch info from the face?

Answer 25

In this case the info would be carried in the trigeminal nerve

1) Primary cell body in the trigeminal ganglion
2) Primary axon enters the brainstem and passes striagh into the pontine nucleus
3) Secondary cell body located in pontine nucleus where primary and secondary neurone synapse
4) Secondary axon crosses the midline and ascends to the thalamus in the trigeminothalamic tract

Question 26

Does the trigeminothalamic tract carry info from the contralateral or ipsilateral side of the head?

Answer 26

Contralateral

Question 27

Which neuron in the trigeminal sensory pathway crosses the midline?

Answer 27

Secondary neuron axon

Question 28

What kind of fibres carry discriminatory touch info from the head?

Answer 28

Fat, fast fibres

Question 29

What 2 groups do somaesthetic modalities from the head fall into?

Answer 29

1) Modalities that are essential to survival - pain, temp, some touch and pressure
2) Modalities that increase detail - discriminative touch: 2 point discrimination and vibration, proprioception

Question 30

What would be the course of neurones carrying proprioceptive information from the muscles of mastication?

Answer 30

Info would be carried in the trigeminal nerve

1) Primary neuron cell body within the mesencephalic nucleus - gives off 2 axons
2) One axon synapses with a secondary sensory neurone just outside of the mesencephalic nucleus - the axon of which then ascends to the thalamus in the trigeminothalamic tract
3) The other axon travels to the motor trigeminal nucleus where it synapses with the cell body of a motor neurone
4) Axon of the motor neurone then travels to the muscles of mastication

Question 31

Proprioceptive information from the head travels to which part of the trigeminal nucleus?

Answer 31

Mesencephalic nucleus