Trigeminal Pathways

Question 1

Discuss the organization of the sensory and motor trigeminal nuclei in the brainstem

Answer 1

3 central trimgeminal sensory nuclei

1. mesencephalic
   
   2. principal (main) sensory
      
      • fine touch, vibration
   3. spinal (descending) trigeminal
      
      • pain, temperature

Question 2

Compare and contrast how nociceptive, proprioceptive and tactile information from the face are centrally processed

Answer 2

a

Question 3

Describe thalamic and cortical mechanisms that produce somatic sensation in trigeminal dermatomes

Answer 3

a

Question 4

Understand the impact of pathway lesions on sensation in the face

Answer 4

a

Question 5

three principal branches

Answer 5

ophthalmic, maxillary and mandibular. Of these, the first two carry only somatosensory fibers whereas the mandibular division innervates the masseter muscles (and a few others) as well.

Question 6

sensory information can be divided into two functionally independent systems

Answer 6

one dealing with pain & temperature, the other with touch, vibration and position sense. Similarly, sensory information traveling in the trigeminal nerve is divided up into different functional processing systems in the central nervous system. Therefore, you would logically conclude that you need to be on the lookout for three things in the brainstem: 1) trigeminal motor nucleus, 2) a trigeminal pain & temperature nucleus (spinal trigeminal nuc.), and 3) a trigeminal touch-vibration-position nucleus (main sensory nuc.).

Question 7

Main (chief or principal) Sensory Nucleus

Answer 7

the main sensory nucleus deals with touch, vibration and position sense.

Question 8

Spinal Trigeminal Nucleus

Answer 8

Although the lower part of the spinal trigeminal nucleus deals with pain and temperature information (like the substantia gelatinosa of the spinal cord), the upper half of the spinal trigeminal nucleus is involved in other functions such as trigeminally-mediated reflexes

Question 9

Trigeminal Motor Nucleus

Answer 9

where the motor neurons of the trigeminal nerve live. This is analogous to the ventral horn.

Question 10

Afferent Supply

Answer 10

Ipsilateral)

• To face
• To the top of the head
• To the eardrum
• Anterior 2/3 of tongue (VII does taste!)
• Proprioceptors for the jaw
• *The teeth, cornea and eardrum are 3 regions where there is only pain sensation**

Question 11

Efferent Motor Output

Answer 11

(Ipsilateral)

• Muscles of mastication (derived from first branchial arch)
• Tensor tympani – little muscle in ear, tenses eardrum to prevent too much sound transmission