White Matter

Question 1

What is white matter made up of ?

Answer 1

predominantly nerve fibres, neuroglia and blood vessels

Question 2

White matter – divisible into:

Answer 2

• Anterior funiculus
• Lateral funiculus
• Posterior funiculus

Question 3

Arrangement of nerve fibers in white matter?

Answer 3

Nerve fibres are grouped into a number of ascending (sensory) and descending (motor) tracts

Question 4

What are ascending tracts?

Answer 4

carry afferent or sensory information from the periphery to higher centers

Question 5

The sensory information is divided into ?

Answer 5

-Exteroceptive sensation which originates from outside the body, such as pain, temperature, touch and pressure
-Proprioceptive sensation which from inside the body, for example from muscles and joints

Question 6

AH cells in the anterior horn (motor column): Divided into:

Answer 6

Central, medial and lateral groups.

Question 7

AH cells in the anterior horn (motor column):
Central group -Forms three definite nuclei

Answer 7

• Phrenic nucleus – extends from C3-C5, innervates the diaphragm
• Spinal nucleus of accessory – extends from C1- C5, innervates trapezius and sternocleidomastoid
• Lumbosacral nucleus – extends from L2-S1, function is not known

Question 8

Arrangement of AH cells in the anterior horn (motor column): Medial Group

Answer 8

->dorsomedial and ventromedial group
* Neurons in this group extend throughout the length of the cord
* Supply muscles of neck and trunk

Question 9

Arrangement of AH cells in the anterior horn (motor column): Lateral group

Answer 9

->ventro-lateral, dorso-lateral and retro-dorso-lateral group
->Ventro-lateral – for the supply of shoulder and arm (cervical enlargement: C5-T1) or hip and
thigh (lumbar enlargement: L2-S2)
->Dorso-lateral – for forearm (C4-T1) or leg (L2-S2)
->Retro-dorso-lateral – for the supply of hand (cervical – C8,T1) or foot (lumbar – S1,2,3)
- Neurons in this group also supply perineal muscles (anal and urethral muscles) (damage to this nucleus results in rectal and urinary incontinence).
* Neurons in this group are confined to the cervical and lumbar enlargements
* Supply the upper and lower limb muscles

Question 10

What is Polio?

Answer 10

Paralysis of muscles due to destruction of ventral horn cells of the spinal cord by the polio virus.

Question 11

What is Posterior horn?

Answer 11

• Divisible into apex, head, neck and base.
• Contains sensory neurons.

Question 12

The neuronal groups in this Posterior horn are :

Answer 12

• Substantia gelatinosa (Lamina 2)
  ->Receives afferents concerned with PAIN, TEMP, & TOUCH from the posterior root.
• Nucleus proprius (Lamina 3,4,5,6)
  ->Receives fibers from the posterior white column that are concerned with the senses of position, and movement, two point discrimination, & vibration.
• Nucleus dorsalis (Lamina 7)
  ->* Most of the neurons are associated with proprioceptive endings (neuromuscular spindles and tendon spindles)
• Visceral afferent (T1 - L3 and S2-S4 segment)
  ->* Receives visceral afferent information’s