Spinal Cord Gray Matter Flashcards
As the root fibers enter the spinal cord, they bifurcate into:
- Long ascending fibers form long tracts
- Short descending tracts form short intersegmental tracts
Describe the general gross structure of gray matter of spinal cord
- 2 Posterior horns extending almost to the surface
- 2 Anterior horns but do not extend to surface
- Two lateral horns at base of ant horn in thoracic & upper lumbar only
- Central canal in gray commissure lined by ependymal cells
Mention the types of cells in the posterior horn
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
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 …..
Posteromedial (pericornual)
Substantia gelatinosa
Nucleus proprius
Reticular nucleus
Dorsal nucleus of Clark
Describe function of intermedio-medial nucleus
Serves as intermediate relay in transmission of visceral afferent impulses to visceral efferent neurons.
Which nucleus(ei) form the intersegmental tracts?
Posterior and anterior commissural nuclei
Mention level of Clarke’s nucleus
C8-L3
The medial group of nuclei of ant horn supply …..
Sk musckes of neck & back (axial)
Enmerate nuclei of ant horn
Med group: antro & postromedial
Lat: anterior, centra, antrolateral, postrolateral, retropostrolateral
The hand is supplied by ….. while foot is supplied by …..
Retropostrolateral column in cervical
Same in lumbar
Flexor muscles are supplied by ….while extensors by ….
Dorsal region
Ventral region
In Thoracic segment, there is ….. supplying muscles of trunk & intercostals
Single lateral nucleus
The ….. give rise to preganglionic sympathetic fibers while …..gives rise to preganglionic parasympathetic fibers
Intermediolateral nucleus
Sacral autonomic nuclei
Lateral part of lamina V corresponds to ….
Reticular nucleus
Mention nuclei of lamina VII
Clarke’s, intermedi-medial & internedio-lateral nuclei
The lamina which recieves termination of extrapyramidal tracts
Lamina VIII
Describe role of laminae IX & X
IX: corresponds to nuclear group of ant horn (medial & lateral motor nuclear group)
X: represents central grey substance around central canal
Enumerate short tracts
Comma-shaped, septomarginal, Lissauer’s & Fasciculus proprius
Enumerate functions gamma efferent fibers
- Maintains muscle spindle sensitvity during skeletal muscle contraction (prevent unloading)
- Stimulation of gamma efferents results in skeletal muscle contraction
- It is one of the sites of higher supraspinal control on stretch reflex
Enumerate functions of stretch reflex
- Skeletal muscle tone
- Servo-assisstance function (force regulation)
- Damping action
- Examination of stretch reflex has clinical value
It is also helpful in: - Allow nervous system to produce strong contraction with minimal energy
- Application of heavier load with stabilization of limb postion (load reflex)
- Compensate for muscle weakness or muscle fatigue or failure of muscle to contract in adequate force.
GRs for Muscle tone
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.
Mention functions of muscle tone
- Maintain body posture against gravity
- Gives postural background enables performance of voluntary movements
- Maintain heat production thus regulate body temp
- Maintain venous return & lymphatic return esp muscles of LL
- Keep viscera in position by abdominal muscles
