Organisation of the Spinal Cord

Question 1

What is the spinal cord?

Answer 1

Near cylindrical column that is surrounded by dura mater, arachnoid and pia mater and is continuous with the corresponding membranes of the brain

Question 2

To what vertebral level does the spinal cord extend?

Answer 2

L1/L2

Question 3

How many spinal nerves are there?

Answer 3

31

Question 4

What are the functions of the spinal cord?

Answer 4

Homeostasis - acts as integrating centre for spinal reflexes

Relay conduit - involved in impulse propagation to and from the brain via tracts

Question 5

Describe the different cell types/neurones in the spinal cord and their prevalence

Answer 5

Projection neurones - give rise to axons of ascending pathways (~1% in spinal cord)
Motor neurones - innervate muscle fibres (~2% in spinal cord)
Interneurones - cells which modulate sensory input (~97% in the spinal cord)

Question 6

What are the two divisions of the spinothalamic tract?

Answer 6

Lateral and anterior

Question 7

Describe the lateral spinothalamic tract

Answer 7

Conveys pain and temperature, decussates at level of spinal entry and carries information to the VPN in the thalamus and the somatosensory cortex

Question 8

Describe the anterior spinothalamic tract

Answer 8

Conveys information about crude touch, decussates at spinal level and travels to the VPN of the thalamus and then to the somatosensory cortex of the postcentral gyrus

Question 9

Where is the somatosensory cortex?

Answer 9

Lateral postcentral gyrus

Question 10

Describe the DCML tract

Answer 10

Conveys fine touch, vibration, two point discrimination and proprioception from the skin and joints, to the spinal cord then to the gracile/cuneate nuclei in the lower medulla where the tract decussates and travels to the thalamus and postcentral gyrus (somatosensory cortex)

Question 11

What is the gracile fasciculus?

Answer 11

Carries information about proprioception etc. from the lower part of the body

Question 12

What is the cuneate fasciculus?

Answer 12

Carries information about proprioception from the upper part of the body

Question 13

Describe the corticospinal tract

Answer 13

Sends out motor information to stimulate voluntary movement: cerebral cortex –> medullary pyramids (decussation) –> synapse with LMNs at spinal level of muscle they innervate

Question 14

What are axons called that cross in the medulla?

Answer 14

Internal arcuate fibres

Question 15

What is meant by tract lamination?

Answer 15

Sacral segments tend to be most lateral in the tracts, except for in the dorsal funiculus where the sacral aspect is most medial

Question 16

Define ‘receptive field’

Answer 16

Particular region of the sensory space in which a stimulus will trigger the firing of a particular sensory neurone