Spinal Cord Morphology

Question 1

What are the three major pathways?

Answer 1

Association pathways - axons connect different corical areas within a hemisphere

Commissural pathways - axons connect ares on boths sides of the brain (generally homotopic)

Projection pathways - Axons connect different areas, ascending or descending

Question 2

What are afferent pathways?

Answer 2

Input for example sensory

Question 3

What are efferent pathways?

Answer 3

Output for example motor

Question 4

Where are the two enlargements of the spinal cord?

Answer 4

Cervical - C5 to T1

Lumbar - L2 - S3

Question 5

What is the pyramidal decussation?

Answer 5

Region where some descending pathways cross

Question 6

What are the three columns of white matter that surround the gray matter?

Answer 6

Anterior funiculus

Lateral funiculus

Posterior funiculus

Question 7

Where is the coricospinal tract located within the spinal cord?

Answer 7

Descends the cord within the lateral funiculus

Principal targets are neurons concerned with the activation of skeletal muscles

Question 8

What is the distribution of segments in the human spinal cord?

Answer 8

8 cervical

12 thoracic

5 lumbar

5 sacral

1 Coccygeal

Question 9

What levels of the spinal cord is there a lateral horn (gray matter) present?

Answer 9

The 12 thoracic and upper two or three lumbar levels

Question 10

Where do axons pass from one side of the spinal cord to the other?

Answer 10

Anterior white and gray commissures

Question 11

What are fasiciculi composed of?

Answer 11

Central processes of peripheral sensory neurons supplying muscles, joints and skin

Question 12

What is Lissauer’s tract?

Answer 12

Compact bundle of small fibers, part of the pain pathway, that lies on the periphery of the spinal cord

Question 13

Where is the proportion of gray matter to white matter the greatest?

Answer 13

Lumbar and Cervical enlargements

Question 14

Describe the gray matter in the cervical region

Answer 14

The dorsal gray column is comparatively narrow and the ventral column is broad and expansive

Question 15

Describe the gray mater in the thoracic region

Answer 15

Both dorsal and ventral columns are narrow

A lateral column is present

Question 16

Describe the gray matter in the lumbar region

Answer 16

The dorsal and ventral columns are broad

Question 17

Describe the blood supply to the spinal cord.

Answer 17

Two posterior spinal arteries supply the dorsal horns

One anterior spinal artery territory supplies the ventral horns

Question 18

Describe the stretch reflex

Answer 18

Muscle spindles are excited and in turn excite synergistic alpha motor neurons

Reciprocal inhibition occurs

Question 19

How is autogenic inhibition manifested clinically in certain pathological conditions?

Answer 19

Clasp-knife reflex

Mediated by Ib fibers from golgi tendon organs

Question 20

Why can only noxious stimuli illicit the flexor reflex?

Answer 20

Descending influences normally hold the reflex in a somewhat inhibited state

Question 21

What are the two ways the flexor reflex pathway spreads over multiple spinal segments?

Answer 21

Primary afferent fibers bifurcate on entering, and their processes then extend in both directions

The interneuron itself may have processes extending over severeal segments

Question 22

Why doesn’t the flexor reflex cause falling over?

Answer 22

The contralateral limb is stimulated to extend to support the weight of the body