spinal cord

Spinal Cord
?Within bony vertebral column.
?Cylindrical of soft tissue (little finger).
?Cross-section ? central butterfly (gray matter):
i.Interneuron
ii.Cell bodies
iii.Dendrites of efferent neurons
iv.Entering fibers of afferent neurons
v.Glial cells.

Spinal Cord
?Gray matter (Lacks myelin).
?White matter
–Myelinated axons of interneuron “fiber tracts or pathways”.
1)Descending: Relay information from brain to spinal cord.
2)Ascending: Transmit information to brain.
3)Others: Transmit information between different levels of brain and spinal cord.
Spinal Cord
?Afferent fibers enter spinal cord via dorsal root.
?Cell bodies of the afferent neurons “dorsal root ganglia.
?Efferent neurons leaves spinal cord via ventral roots.
–Dorsal and ventral roots from same level combine ? spinal nerve, one on each side of spinal cord.


Motor Functions of the Spinal Cord
(Cord Reflexes)
Reflex
?An involuntary motor response to an adequate sensory stimulus that occurs subconsciously, without the mediation of the cerebral cortex
?i.e., withdrawal reflex.
Characters of Reflex Action
1.Important role in protection of the body.
2.Responsible for maintenance of:
a. muscle tone.
b. body posture.
3.Center can be anywhere except cerebral cortex.
4.Center can be in spinal cord or in brain stem.