#12

Question 1

While the conscious spinal pathways converge on the VPL thalamus, all
conscious trigeminothalamic pathways converge on the

Answer 1

VPM nucleus of the thalamus

Question 2

Posteromarginal nucleus, substantia gelatinosa and nucleus proprius blend with the a. neurons in the a receive pain and temperature
information from face; those in dorsal horn the same but from the body

Answer 2

spinal nucleus of trigeminal nerve which extends from the pontomedullary junction downward into C2 or 3

Question 3

the spinal trigeminal tract merges with
a as it descends. This tract consists of
descending branches of Aδ and C fibers derived from
the trigeminal ganglion, just as a
consists of ascending branches of Aδ and C fibers
derived from DRG cells in the upper cervical spinal
cord. . Spinal tract of V anda essentially
merge going opposite directions but carrying the same
kinds of signals: GSA pain and temperature (spinal
tract from face, a from upper neck)

Answer 3

Lissauer’s tract

Question 4

The trigeminal nerve enters the brainstem at the a by passing through the substance of b

Answer 4

a pons
b the middle cerebellar peduncle.

Question 5

SPINAL TRACT AND NUCLEUS OF CN V

Answer 5

Conveys pain, temperature, and crude touch from the face, head, nasal and oral cavities
The spinal tract is composed of 1st-order Aδ and C fibers and refers to the central processes of pseudo-unipolar trigeminal ganglion neurons running downward to terminate in the spinal nucleus (2nd-order neurons)

Question 6

Pain from teeth ends in a parts of spinal
trigeminal nucleus (as would be expected for alveolar branches of V2 and V3 nerves)

Answer 6

middle (interpolar) and rostral (oral)

Question 7

. MAIN (PRINCIPLE) SENSORY NUCLEUS OF CN V

Answer 7

Receives 1st-order discriminative touch sensation from the head and face, but not proprioception.

Question 8

MESENCEPHALIC NUCLEUS OF CN V (meV)

Answer 8

This is the sensory nucleus and tract that processes nonconscious proprioceptive (and some conscious) information from the face and head. Though primarily concerned with proprioceptive information from the muscles of mastication, the mesencephalic nucleus transmits information from the periodontal ligament (for bite force control) and the facial and tongue muscles. If it’s proprioception, and it’s coming from the head/face, it uses the mesencephalic nucleus to signal.

Question 9

the only structure in the human CNS to contain primary
afferent cell bodies

Answer 9

The neurons of the mesencephalic nucleus are primary afferent neurons that ended up in the midbrain. There are virtually no classical chemical synapses in meV; communication is by electrical gap junctions

Question 10

The mesencephalic nucleus sends axons to the a located between the motor nucleus and main sensory nucleus; this transmits conscious proprioception about jaw and tongue position

Answer 10

supra-trigeminal nucleus (S-TN)

Question 11

The major output target of the mesencephalic nucleus is the motor nucleus of V (moV), for participation in

Answer 11

The jaw-jerk reflex
A simple, consensual reflex elicited by tapping the chin with the jaw open. This reflex is difficult to elicit in healthy individuals but is exaggerated in corticobulbar lesions—i.e., UMN signs resulting from damage to corticobulbar inputs to moV.

Question 12

2nd-order fibers from all modalities (spinal nucleus, main sensory nucleus, and supra-trigeminal nucleus) cross diffusely to form the a, which terminates in the b

Answer 12

a VTT
b VPM (ventral posteromedial) nucleus of the thalamus

Question 13

VTT fibers from the spinal nucleus run a aspect of the
spinothalamic tract (STT).

Answer 13

a alongside the medial

Question 14

VTT fibers from the main sensory nucleus and supra-trigeminal nucleus a the medial lemniscus (ML).

Answer 14

run alongside

Question 15

Some discriminative touch axons from the main sensory nucleus stay uncrossed and ascend as a A. Therefore, it is very unusual to
lose all sensations on one side of the face

Answer 15

dorsal trigemino-thalamic tract (DTT)

Question 16

Crossed VTT fibers and uncrossed DTT fibers form the a, which terminates in the ventral posterior medial nucleus of the thalamus (VPM).

Answer 16

trigeminal lemniscus

Question 17

In the midbrain, the trigeminal lemniscus runs a to the medial lemniscus and spinal lemniscus in the b

Answer 17

a medial
b lateral tegmentum

Question 18

Now all three major somatosensory tracts (VTT, DCML, STT) share the same vascular territory:

Answer 18

the lateral posterior choroidal artery.