5 & 6 SPINAL CORD AND BRAINSTEM

Question 1

Which part of the spinal cord carries discriminate sensory information for the upper limb

Answer 1

The gracile fasciculi. Should be present from around T6.

Question 2

What separates the gracile and cuneate fasciculi

Answer 2

The dorsal intermediate sulcus

Question 3

Describe in general the motor and sensory pathways through the brainstem. (ventral dorsal)

Answer 3

Motor- ventral.

Sensory- dorsal

Question 4

Describe the passage of motor pathways in the brainstem

Answer 4

Midbrain- crus cerebri (lateral corticospinal, medial corticobulbular)
Pons- pontine nuclei
Medulla- pyramids

Question 5

Describe the passage of sensory information through the brainstem

Answer 5

Brainstem and pons; tegmentum- lies posterior to motor pathways.
Medulla the gracile and cuneate nuclei within the tegmentum.

Question 6

Describe the substantial nigra including function and location

Answer 6

Lies between the crus cerebra and tegmentum in the midbrain.
Dopamine ‘sink’. The largest nuclei in the brain for releasing dopamine. Part of the basal ganglia.

Question 7

What is the most posterior structure in the midbrain and its function

Answer 7

The corpora quadrigemina. Made up of the superior and inferior collicular. The superior is involved in reflex movement of your head towards a visual stimulus and the inferior reflex movement of the head towards auditory stimulus.

Question 8

Where do white matter fibres travel to/from the cerebellum

Answer 8

The cerebellar peduncles inferior to the collicular.

Question 9

Describe the dorsal column medial lemniscal pathway

Answer 9

Discriminative sensory pathway. First order neurons- encapsulated receptors, myelinated, cell bodies in dorsal root ganglion, synapse with 2nd order neurons in lamina 3 and 4 of grey matter or continue to synapse in gracile/ cuneate nuclei in medulla. In the spinal cord they travel in the dorsal funiculus. They decussate at the medulla to the contralateral side of the brainstem while crossing the fibres are known as internal arcuate fibres. They then travel up the medial lemniscus to the VP of the thalamus where they synapse with third order neurons and travel via the internal capsule to the somatosensory cortex.

Question 10

Where do discriminative sensory fibres decussate and what are these fibres called while crossing

Answer 10

At the medulla after the gracile and cuneate nucleus. Called internal arcuate fibres as they cross to the medial lemniscus.

Question 11

Where do discriminative fibre travel to get to the somatosensory cortex from the thalamus

Answer 11

The internal capsule

Question 12

Describe the pathway of non discriminative sensory fibres

Answer 12

First order neurons are free nerve endings. Non or sparsely myelinated fibres. Enter spinal cord via dorsal root ganglion, Travel up a few levels via dorsolateral tract of lissauer then synapse with second order neurons in lamina 1 and 2 and decussate via the anterior white commissure. Travel up the SC on the contralateral side via the ventral funiculus/ lateral spinothalamic tract. The lateral spinothalamic joins the medial lemniscus at around the pons and the second order pain/temp neurons synapse with third order neurons in the VP of the thalamus. Then on to somatosensory cortex.

Question 13

Describe what would happen if there were a unilateral spinal cord lesion at T-4/5.

Answer 13

You would lose discriminative sensation and muscle function one the ipsilateral side to the lesion (below level of lesion) and non-discriminative sensation on the contralateral side to it.

Question 14

What spinal level is the lower neck

Answer 14

C3

Question 15

What spinal level is the nipple line

Answer 15

T4-T5

Question 16

What spinal level is the umbilicus

Answer 16

T10

Question 17

What spinal level is the inguinal ligament

Answer 17

L1

Question 18

Describe the motor pathways through the brainstem

Answer 18

Upper motor neurons in the primary motor cortex (layer V of neocortex, pyramidal cells), travel via internal capsule to brainstem.
Midbrain- ventral aspect of crus cerebri are the corticospinal tract and medially the corticobulbar tract.
Pons via pontine nuclei
Medulla via medullary pyramids where fibres decussate to the lateral funiculus and travel down sc –> synapse with lower motor neurons in lamina 8 and 9 of SC grey matter before exiting the SC through the ventral root.

Question 19

What do the gracile and cuneate funiculi do

Answer 19

Carry discriminative sensory info. Gracile- lower limb, cuneate upper limb

Question 20

What spinal level does the cuneate funiculus start

Answer 20

Around T6

Question 21

Describe the corticobulbar pathway

Answer 21

Follows the same path as corticospinal until Pons where UMN synapse with LMN in pontine nuclei. Tract ends at medulla whereby all signal have exited.

Question 22

Describe an associative sensory loss

Answer 22

Results of a brain stem/ thalamus injury. Whereby you would get discriminative and non discriminative sensory loss on the contralateral side to the lesion.

Question 23

Describe a dissociative sensory loss

Answer 23

When a unilateral spinal cord lesion occurs. Loss of discriminative sensory info on the ipsilateral side to lesion. Loss of non-discriminative sensation on the contralateral side to lesion.