Spinal Cord

Question 1

Describe gross anatomy of spinal cord

Answer 1

Central grey matter, peripheral white matter

Grey matter has a dorsal (sensory) and ventral (motor) horn on each side

White matter is arranged in columns; posterior, lateral and anterior

Question 2

Describe white matter in spinal cord

Answer 2

Columns; posterior, lateral, anterior

Within the columns there are bundles of axons (tracts)

There are 3 important tracts

• Corticospinal/Pyramidal
• Posterior/dorsal column
• Lateral spinothalamic tract

Question 3

Describe the pathway of the Corticospinal/pyramidal tract

Answer 3

Corticospinal tract has 2 neurons; control voluntary movement

• travels from motor cortex (area 4) through posterior limb of IC
• decussate in pyramids of medulla
• travel down spinal cord to supply muscle

Question 4

Describe the pathway of the posterior dorsal column

Answer 4

3 neurons; touch, vibration, proprioception

• 1st order neuron synapses with second order neuron in lower medulla
• 2nd order neuron decussates in medulla
• TRACT NOW CALLED MEDIAL LEMNISCUS and travels to thalamus
• 3rd order neuron begins in thalamus and axons pass through IC where they radiate to post-central gyrus

Question 5

Describe the pathway of the lateral spinothalamic tract

Answer 5

3 neurons

*decussation occurs at level of entry

• 1st order neuron enters and ends at same level.
• 2nd order neuron crosses to lateral column and NOW CALLED LATERAL SPINOTHALAMIC TRACT
• 2nd order ends in thalamus
• 3rd order passes through IC, radiates to post-central gyrus

Question 6

Describe what each of the three main tracts does

Answer 6

Corticospinal/pyramidal = motor impulses from motor cortex (area 4) to skeletal muscles

Posterior/dorsal column = vibration sense, proprioception, tactile localisation and touch

Lateral spinothalamic tract = pain and temperature

Question 7

Describe different lesions in the corticospinal tract and their effects

Answer 7

UMN lesion above decussation
- contralateral spastic paralysis and hyperreflexia

UMN lesion below decussation
- ipsilateral spastic paralysis and hyperreflexia

LMN lesion
- ipsilateral flaccid paralysis and arreflexia

Question 8

Describe the effects of lesions on tone and reflexes

Answer 8

UMN lesion = hyperreflexia and increased tone (spasticity)

LMN lesion = arreflexia and decreased tone (flaccidity)

Question 9

What is the blood supply to the internal capsule

Answer 9

Middle cerebral artery