9 - sensory pathways for head

Question 1

general sensation from head is carried in which cranial nerves

Answer 1

trigeminal, facial, glossopharyngeal and vagus

Question 2

where does each of the sensory cranial nerves supply?

Answer 2

Trigeminal (CN V) - from face, nose, scalp and dura
Facial (CN VII) - from external ear
Glossopharyngeal (CN IX) - posterior 1/3 tongue, pharynx and middle ear
Vagus (CN X) - auditory canal, larynx, pharynx and oesophagus

Question 3

all general sensation information from the head travel in what pathway?

Answer 3

trigeminal sensory

Question 4

what are the 3 sensory trigeminal nuceli? Which nerves go to these?

Answer 4

mesencephalic, chief, spinal

all the general sensory nerves of the face (trigeminal, facial, glossopharyngeal, vagus)

Question 5

which foramen do the different branches of CNV exit?

Answer 5

V1 - SOF
V2 - Foramen rotundum
V3 - foramen ovale

Question 6

primary cell bodies (with the exception of one) are located where?

Answer 6

trigeminal ganglion

Question 7

what do the different branched of the trigeminal nerve supply?

Answer 7

V1 (Opth) - purely sensory
V2 (Mand) - purely sensory
V3 (Max) - sensory (jaw, lower lip, anterior ear), motor (muscles of mastication, ant belly of digastric etc)

Question 8

what modalities do the different part of the trigeminal sensory nuclei recieve?

Answer 8

Mesencephalic - proprioception (exception to rule that primary cell bodies are in periphery)

pontine - discriminative touch

rostral part of spinal nu - simple touch and pressure

caudal part of spinal - pain and temperature

Question 9

describe the pain and temperature pathway

Answer 9

the primary neuron is thin and slow and synapses in the caudal part of the spinal nucleus with the cell bodies in the trigeminal ganglion.

The secondary axon crosses the midline immediately and ascends to the thalamus in the trigeminothalamic tract.

Question 10

describe the crude touch and pressure pathway

Answer 10

the primary neuron synapses with the secondary neuron more rostrally in the spinal nucleus.
It then crosses the midline immediately to ascend to the thalamus also in the trigeminothalamic tract.
All the fibres for the head travel to the VPM in the thalamus (unlike the body where they travel to the VPL).

Question 11

a lesion to the right lateral medulla would cause

Answer 11

Loss of pain, temperature, touch and pressure in the face on the same side of the lesion since the spinal nucleus and spinal tract are affected

Loss pain, temperature, touch and pressure in the body on the opposite side of the lesion since the spinothalamic tract is affected

Question 12

both pain and temperature pathways eventually project to the _____ side. But:
ST - crosses at level of SC entry
TT - ____ spinal tract -> spinal nu -> secondary crosses midline -> ascend up trigeminothalamic

Answer 12

opposite

decends

Question 13

describe the discriminatory pathway

Answer 13

fat, fast fibres
1 - in trigeminal ganglion
2 - in pontine nu, cross midline, ascend in trigeminothalamic tract to VPM of thalamuc
3 - from VPM to SSC

Question 14

describe the proprioception pathway

also explain the jaw jerk reflex

Answer 14

1 - primary axon mostly travels in V1. Primary cell body in mesencephalic nu. Synapse just adj to nu
2 - cross midline straight away –> trigeminothalamic

OR

1 - primary cell body in mescen nu, some fibres contact motor nu (just medial), motor fibres to muscles of mastication = JAW JERK REFLEX