9 - Spinal Cord Structure and Function

Question 1

The spinal cord is supplied with blood by branches of what arteries? What veins drain the blood?

Answer 1

The anterior spinal artery and posterior spinal artery, which arise from the vertebral artery.

Also supplied by multiple radicular arteries from segmental vessels.

Drained by the same named veins.

Question 2

The spinal cord extends from the ______ at the foramen magnum to the lower border of ___.

Answer 2

Medulla

L1

Question 3

At what level is the conus medullaris? At what level would you do an LP?

Answer 3

L1 and L2

L4-L5

Question 4

What is the cauda equina?

Answer 4

The lumbosacral roots surrounding the filum terminale.

Question 5

How are spinal nerves segmented?

Answer 5

There’s 31 pairs of spinal nerves:

• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 1 coccygeal

Question 6

Each spinal nerve (except C1) innervates a single ________ dermatome. Each spinal nerve also innervates a single ______ myotome.

Answer 6

ipsilateral.

ipsilateral

Question 7

What is referred pain?

Answer 7

Convergence of somatic and visceral afferents.

Question 8

How do spinal nerves exit the vertebral canal?

Answer 8

Via the intervertebral foramina, which is the location of the DRG.

Question 9

What are the five indentations on the spinal cord? What is the purpose of each indentation?

Answer 9

1. anterior median fissure - anterior spinal artery and vein
2. Posterior median sulcus (septum)
3. Posterolateral sulcus (entry of dorsal roots)
4. Anterolateral sulcus (exit of ventral roots)
5. Posterior intermediate sulcus (cervical and upper thoracic only, which separates the major ascending tracts)/

Question 10

Where are the white and gray matter of the spinal cord?

Answer 10

The white matter (axons and glia) surrounds the H-shaped gray matter (cell bodies and glia) with the central canal containing CSF in the middle.

Question 11

Where is the spinal cord the largest and smallest? How does the amount of white matter change?

Answer 11

Largest at the cervical enlargement and smallest at the sacral level.

Amount of white matter decreases as you move caudally.

Question 12

How does the amount of gray matter in the sp cord change?

Answer 12

It varies; it’s greatly expanded at the cervical and lumbar enlargements, especially in the ventral horns.

Question 13

What are the divisions of the white matter?

Answer 13

Posterior funiculus (dorsal column), lateral funiculus, and anterior funiculus.

Question 14

What is located in the posterior funiculus of the white matter?

Answer 14

Ascending somatosensory fibers, fasciculus gracilic (sacral and lumbar), and fasciculus cuneatus (thoracic and cervical).

Question 15

What is the gray matter of the spinal cord subdivided into?

Answer 15

Dorsal horn
Ventral horn
Lateral horn

Question 16

What is the function of the dorsal horn of the spinal cord gray matter?

Answer 16

Sensory:

• recieves sensory input
• mediates synapses
• gives rise to ascending sensory pathways

Question 17

What is the function of the ventral horn of the gray matter of the spinal cord?

Answer 17

• Houses alpha and gamma motorneurons
• Houses interneurons
• Neurons innervate extrafusal and intrafusal muscle fibers

Question 18

What is the function of the lateral horn of the gray matter of the spinal cord? Where is it located?

Answer 18

Also called the intermediolateral cell column.

Located at levels T1-L2-3

Responsible for thorcolumbar sympathetic outflow (preganglionic).

Question 19

The spinal cord recieves primary sensory inputs from the _____ at each segment and relays them to the brain stem, cerebellum, of thalamus. These inputs may not ______ first within the spinal cord.

Answer 19

DRG

Synapse

Question 20

The spinal cord houses the intermediolateral cell column from T1 to L2/3 that give rise to preganglionic sympathetic fibers what synapse where?

Answer 20

In paravertebral and prevertebral ganglia.

Question 21

What is the doctor term for dorsal root lesions and what do they cause?

Answer 21

Dorsal Rhizotomy

Hypesthesia (a diminished capacity for physical sensation) or anesthesia

Question 22

What symptoms will result from ventral root lesions?

Answer 22

Weakness or flaccid paralysis and atrophy of muscles.

Involvement of autonomic preganglionic fibers may result in autonomic dysfunction.

Question 23

What does spinal cord hemisection result in?

Answer 23

Brown-Sequard syndrome

Loss of fine touch, vibration, and proprioception ipsilateral to and below the lesion.

Loss of pain and temp contralateral to and below the lesion.

Spastic paralysis ipsilateral to and below the lesion.

Question 24

What can result from spinal cord transection?

Answer 24

Destruction of ascending and/or descending tracts that produces sensory, motor, or mixed deficits.

Question 25

What is syringomyelia?

Answer 25

Damage to crossing fibers around the central canal.