Anatomy #61 ( grey matter, white matter, and spinal cord cont.)

Grey matter is located

located in core, white matter outside

Gray matter and spinal roots

– Cross section of cord resembles butterfly or letter “H”

– Three areas of gray matter are found on each side of center and are mirror images:

Dorsal horns

interneurons that receive somatic and visceral sensory input

ventral horns

some interneurons; somatic motor neurons

Lateral horns

sympathetic neurons

-only in thoracic & superior lumbar regions

Gray commissure:

bridge of gray matter that connects masses of gray matter on either side

-Encloses central canal

Ventral roots:

bundle of motor neuron axons that exit the spinal cord

Dorsal roots:

sensory input to cord

Dorsal root (spinal) ganglia:

cell bodies of sensory neurons

Spinal nerves:

formed by fusion of dorsal and ventral roots

how many groups does grey matter divde into

4 groups

-based on of somatic or visceral innervation

White matter

Myelinated and nonmyelinated nerve fibers allow communication between parts of spinal cord, and spinal cord and brain

white matter runs in 3 directions

-ascending

-descending

-transverse

ascending

up to higher centers (sensory inputs)

descending

from brain to cord or lower cord levels (motor outputs)

transverse

from one side to other (commissural fibers)

• White matter is divided into how many columns

• 3 white columns (funiculi) on each side

• -dorsal (posterrior) , lateral, ventral (anterior)

Each spinal tract is composed of

axons with similar destinations and functions