Spinal Cord

Question 1

Which part of the spinal cord is made of grey matter?

Answer 1

The middle (that looks like an X)

Question 2

Which part of the spinal cord is made of white matter?

Answer 2

The outside

Question 3

What are the four levels of spinal cord?

Answer 3

• Cervical

• Thoracic

• Lumbar

• Sacral

Question 4

Which part of the spinal grey matter does information come into?

Answer 4

Dorsal horn

Question 5

Which part of the spinal grey matter does information leave from?

Answer 5

Ventral grey matter

Question 6

Where are motor neurones located in the spinal cord?

Answer 6

Ventral spinal cord

Question 7

What does somatotopic mean?

Answer 7

That space is related to locations on the body such that adjacent neurones in the neural tissue respond selectively to stimuli presented to adjacent locations in the body (i.e. further in spine, further in body)

Question 8

What are the two major descending systems of spinal white matter?

Answer 8

• Lateral descending system

• Medial descending system

Question 9

What are the two major ascending systems?

Answer 9

• Dorsal column pathway

• Spinothalamic pathway

Question 10

What are the two tracts that make up the lateral descending system?

Answer 10

• Corticospinal (from cortex)

• Rubrospinal (from red nucleus)

Question 11

What are the two tracts that make up the medial descending system?

Answer 11

• Vestibulospinal (from vestibular nuclei)

• Reticulospinal (from reticular nuclei)

Question 12

Describe the structure of the lateral descending system

Answer 12

• Fibres of the lateral system are in the dorso-lateral part of the spinal cord

• They connect to motor neurones in the lateral part of the ventral horn

Question 13

What are the functions of the lateral descending system?

Answer 13

• Corticospinal fibres control movement of every part of the body and is very important for individual finger use

• Other descending fibres, primarily the rubrospinal tract, can compensate partially for the loss of descending corticospinal input

Question 14

Describe the structure of the medial descending system

Answer 14

• Fibres of the medial system are in the ventro-medial part of the white matter

• They connect to motor neurones in the medial part of the ventral horn

Question 15

What are the functions of the medial descending system?

Answer 15

• Control of balance and posture

• Vestibulospinal tract retains balance when the body is moved (external disturbance)

• Reticulospinal tract helps us retain posture and balance during our own volitional movements (internal disturbance)

Question 16

What does the dorsal column pathway do?

Answer 16

Carries sensory information from the joint and skin about:

• Fine touch

• Vibration

• Two-point discrimination

• Proprioception from the skin and joints

Question 17

What does the lateral spinothalamic tract do?

Answer 17

Conveys:

• Crude touch (a sense of being touched without knowledge of where)

• Pain

• Temperature

Question 18

What does DRG stand for and what are they?

Answer 18

• Dorsal root ganglion

• Cell bodies of incoming sensory neurones which sit outside the spine

Question 19

How many pairs of spinal nerves are there?

Answer 19

31

Question 20

What is a dermatome?

Answer 20

An area of the skin supplied by nerves from a single spinal root

Question 21

What is two-point discrimination?

Answer 21

The ability to discern that two nearby objects are touching the skin

Question 22

Why are there spinal enlargements?

Answer 22

The arms and legs have many highly innervates muscles and a high density of sensory receptors so need more nerves

Question 23

What are the two types of tetanic contractions?

Answer 23

Unfused and fused

Question 24

What is the size principle?

Answer 24

With increasing strength of input onto motor neurones, smaller motor neurones are recruited first and fire action potentials before larger motor neurones are recruited