Spinal Cord Gray Matter

Question 1

As the root fibers enter the spinal cord, they bifurcate into:

Answer 1

1. Long ascending fibers form long tracts
2. Short descending tracts form short intersegmental tracts

Question 2

Describe the general gross structure of gray matter of spinal cord

Answer 2

1. 2 Posterior horns extending almost to the surface
2. 2 Anterior horns but do not extend to surface
3. Two lateral horns at base of ant horn in thoracic & upper lumbar only
4. Central canal in gray commissure lined by ependymal cells

Question 3

Mention the types of cells in the posterior horn

Answer 3

Golgi type I: cells with long axons forming long ascending tracts
Golgi type II: cells with short axons terminate in the gray matter near their origin

Question 4

With regards nuclei of the posterior horn, the one at the tip is ….., the cap-like nucleus is ….., ant to it is ….., then lateral to the latter is ….., and the one at medial part of base of post horn is …..

Answer 4

Posteromedial (pericornual)
Substantia gelatinosa
Nucleus proprius
Reticular nucleus
Dorsal nucleus of Clark

Question 5

Describe function of intermedio-medial nucleus

Answer 5

Serves as intermediate relay in transmission of visceral afferent impulses to visceral efferent neurons.

Question 6

Which nucleus(ei) form the intersegmental tracts?

Answer 6

Posterior and anterior commissural nuclei

Question 7

Mention level of Clarke’s nucleus

Answer 7

C8-L3

Question 8

The medial group of nuclei of ant horn supply …..

Answer 8

Sk musckes of neck & back (axial)

Question 9

Enmerate nuclei of ant horn

Answer 9

Med group: antro & postromedial
Lat: anterior, centra, antrolateral, postrolateral, retropostrolateral

Question 10

The hand is supplied by ….. while foot is supplied by …..

Answer 10

Retropostrolateral column in cervical
Same in lumbar

Question 11

Flexor muscles are supplied by ….while extensors by ….

Answer 11

Dorsal region
Ventral region

Question 12

In Thoracic segment, there is ….. supplying muscles of trunk & intercostals

Answer 12

Single lateral nucleus

Question 13

The ….. give rise to preganglionic sympathetic fibers while …..gives rise to preganglionic parasympathetic fibers

Answer 13

Intermediolateral nucleus
Sacral autonomic nuclei

Question 14

Lateral part of lamina V corresponds to ….

Answer 14

Reticular nucleus

Question 15

Mention nuclei of lamina VII

Answer 15

Clarke’s, intermedi-medial & internedio-lateral nuclei

Question 16

The lamina which recieves termination of extrapyramidal tracts

Answer 16

Lamina VIII

Question 17

Describe role of laminae IX & X

Answer 17

IX: corresponds to nuclear group of ant horn (medial & lateral motor nuclear group)
X: represents central grey substance around central canal

Question 18

Enumerate short tracts

Answer 18

Comma-shaped, septomarginal, Lissauer’s & Fasciculus proprius

Question 19

Enumerate functions gamma efferent fibers

Answer 19

1. Maintains muscle spindle sensitvity during skeletal muscle contraction (prevent unloading)
2. Stimulation of gamma efferents results in skeletal muscle contraction
3. It is one of the sites of higher supraspinal control on stretch reflex

Question 20

Enumerate functions of stretch reflex

Answer 20

1. Skeletal muscle tone
2. Servo-assisstance function (force regulation)
3. Damping action
4. Examination of stretch reflex has clinical value
   It is also helpful in:
5. Allow nervous system to produce strong contraction with minimal energy
6. Application of heavier load with stabilization of limb postion (load reflex)
7. Compensate for muscle weakness or muscle fatigue or failure of muscle to contract in adequate force.

Question 21

GRs for Muscle tone

Answer 21

Static component of stretch reflex, because:
-Distance between origin & insertion of muscles is greater than its original length
-Gravity exerts stretch mainly on the antigravity muscles
-Continuous gamma static efferent discharge, leads to continuous stretch of chain fibers.

Question 22

Mention functions of muscle tone

Answer 22

1. Maintain body posture against gravity
2. Gives postural background enables performance of voluntary movements
3. Maintain heat production thus regulate body temp
4. Maintain venous return & lymphatic return esp muscles of LL
5. Keep viscera in position by abdominal muscles