Lecture 4

Question 1

What are the dimensions and termination point of the adult spinal cord?

Answer 1

Length: 42–45 cm
Diameter: 1–2 cm
Terminates around L1–L2 vertebrae

Question 2

What are the cervical and lumbar enlargements?

Answer 2

Cervical (C4–T1): innervates upper limbs
Lumbar (L1–S3): innervates lower limbs

Question 3

What is the cauda equina?

Answer 3

A bundle of lumbar and sacral nerve roots extending beyond the conus medullaris.

Question 4

How many spinal nerve pairs are there?

Answer 4

31 pairs:

8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

Question 5

What is a dermatome?

Answer 5

A region of skin innervated by a specific spinal nerve.

Question 6

What are the functions of the spinal cord grey matter horns?

Answer 6

Dorsal horn: 2° sensory neurons
Ventral horn: lower motor neurons (LMNs)
Lateral horn: autonomic motor neurons (thoracic/lumbar only)

Question 7

What are the three white matter columns in the spinal cord?

Answer 7

Dorsal columns: ascending sensory tracts
Lateral columns: mixed tracts
Ventral columns: descending motor tracts

Question 8

What does the spinothalamic tract carry?

Answer 8

Pain, temperature, and crude touch

Question 9

Describe the spinothalamic tract pathway.

Answer 9

1° neuron: dorsal root ganglion
2° neuron: dorsal horn → decussates → ascends contralaterally
3° neuron: thalamus → somatosensory cortex

Question 10

What does the dorsal column tract carry?

Answer 10

Fine touch and proprioception

Question 11

Describe the dorsal column pathway.

Answer 11

1° neuron: dorsal root ganglion → ascends ipsilaterally
2° neuron: dorsal column nuclei in medulla → decussates
3° neuron: thalamus → somatosensory cortex

Question 12

What are the gracile and cuneate fasciculi?

Answer 12

Gracile fasciculus: medial, carries lower body info (below T6)
Cuneate fasciculus: lateral, carries upper body info (above T6)

Question 13

What does the lateral corticospinal tract control?

Answer 13

Voluntary fine motor control of limbs

Question 14

Describe the lateral corticospinal tract pathway.

Answer 14

Origin: primary motor cortex
Decussation: pyramidal decussation in medulla
Terminates: ventral horn LMNs → skeletal muscle

Question 15

What happens if the spinothalamic tract is damaged?

Answer 15

Loss of pain/temp/crude touch on the contralateral side below the lesion

Question 16

What happens if the dorsal column is damaged?

Answer 16

Loss of fine touch/proprioception on the ipsilateral side below the lesion

Question 17

What happens if the lateral corticospinal tract is damaged?

Answer 17

Ipsilateral spastic paralysis below the lesion (reflexes intact)