Tract of spinal cord consist of bundles of medullated nerve fibers in the dorsal, lateral or ventral white columns or funiculi of the white mater of spinal cord. The fibers having similar origin, termination and function are grouped together and are called as tracts or fasciculi.
Tract of spinal cord may be classified as-
Sensory or ascending tracts
- Sensory or ascending tracts conveying impulses from the periphery to the brain.
- They are generally formed (with exceptions) by the axons of neurons in the dorsal gray column, which in turn receive sensory impulses from the peripheral receptors, through the dorsal roots of spinal nerves after relay in the spinal or dorsal root ganglia.
Motor or descending tracts
- Motor or descending tracts conveying impulses from the brain to the peripheral effectors.
- They arise from different centres or nuclei in the brain, descend in the white mater of spinal cord and finally end in synaptic relations with either somatic motor neurons in the ventral gray column (supplying skeletal muscle) or visceral motor neurons in the lateral gray column (supplying glands, plain muscle and cardiac muscle).
Intersegmental tracts
- Intersegmental tract connecting different segments of the spinal cord.