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Its primary neurons axons enter the spinal cord and then ascend one to two levels before synapsing in the substantia gelatinosa. The tract that ascends before synapsing is known as Lissauer's tract. After synapsing, secondary axons decussate and ascend in the anterior lateral portion of the spinal cord as the spinothalamic tract. This tract ...
The axons of these cells descend from the cortex to form the corticospinal tract. [12] Corticomotorneurons project from the primary cortex directly onto motor neurons in the ventral horn of the spinal cord. [13] [14] Their axons synapse on the spinal motor neurons of multiple muscles as well as on spinal interneurons.
Some axons can extend up to one meter or more while others extend as little as one millimeter. The longest axons in the human body are those of the sciatic nerve, which run from the base of the spinal cord to the big toe of each foot. The diameter of axons is also variable.
This information is then transmitted in axons up the spinal cord in spinal tracts, including the dorsal column-medial lemniscus tract and the spinothalamic tract. The lateral grey column is the third column of the spinal cord. The grey matter of the spinal cord can be divided into different layers, called Rexed laminae. These describe, in ...
The axons of the tract cells cross over (decussate) to the other side of the spinal cord via the anterior white commissure, and to the anterolateral corner of the spinal cord (hence the spinothalamic tract being part of the anterolateral system). Decussation usually occurs 1-2 spinal nerve segments above the point of entry.
The longest axon of a human motor neuron can be over a meter long, reaching from the base of the spine to the toes. Sensory neurons can have axons that run from the toes to the posterior column of the spinal cord, over 1.5 meters in adults. Giraffes have single
Just outside the spinal cord, thousands of afferent neuronal cell bodies are aggregated in a swelling in the dorsal root known as the dorsal root ganglion. [1] [2] All of the axons in the dorsal root, which contains afferent nerve fibers, are used in the transduction of somatosensory information.
The action signal will continue along the central axon of the neuron through the posterior root, into the posterior horn, and up the posterior column of the spinal cord. Axons from the lower body enter the posterior column below the level of T6 and travel in the midline section of the column called the gracile fasciculus. [ 5 ]