Spinal Cord Anatomy
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Discriminative Touch and Kinesthesia Pathway
The ascending pathway for discriminative touch (small receptive field) and kinesthesia (body parts movement sense) begins with encapsulated mechanoreceptors. The associated primary afferent neurons feature large unipolar cell bodies and myelinated axons.
The myelinated axons bifurcate in the dorsal funiculus of the spinal cord and ascend in fasciculus gracilis (pelvic limb and trunk) or fasciculus cuneatus (thoracic limb and neck). The axons in these fasciculi synapse in, respectively, nucleus gracilis or medial cuneate nucleus in the brainstem.
From these nuclei, axons of projection neurons decussate (cross) and run in the medial lemniscus to the contralateral thalamus. Thalamic projection neurons send axons through the internal capsule to the somesthetic area of the cerebral cortex.
The myelinated axons bifurcate in the dorsal funiculus of the spinal cord and ascend in fasciculus gracilis (pelvic limb and trunk) or fasciculus cuneatus (thoracic limb and neck). The axons in these fasciculi synapse in, respectively, nucleus gracilis or medial cuneate nucleus in the brainstem.
From these nuclei, axons of projection neurons decussate (cross) and run in the medial lemniscus to the contralateral thalamus. Thalamic projection neurons send axons through the internal capsule to the somesthetic area of the cerebral cortex.
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