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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 ...
This is in contrast with the dorsal spinocerebellar tract (C8 - L2/L3), which only has 1 unilateral axon that has its cell body in Clarke's column (only at the level of C8 - L2/L3). Originates from ventral horn at lumbosacral spinal levels. Axons first cross midline in the spinal cord and run in the ventral border of the lateral funiculi.
Some neurons are responsible for conveying information over long distances. For example, motor neurons, which travel from the spinal cord to the muscle, can have axons up to a meter in length in humans. The longest axon in the human body belongs to the Sciatic Nerve and runs from the great toe to the base of the spinal cord. These are ...
The upper motor neuron descends in the spinal cord to the level of the appropriate spinal nerve root. At this point, the upper motor neuron synapses with the lower motor neuron or interneurons within the ventral horn of the spinal cord, each of whose axons innervate a fiber of skeletal muscle. [1] [2]
Each area is made up of many segments. Motor and sensory nerve fibers to and from every area of the body are found in the spinal nerve. A dermatome is innervated by each segment of the spinal cord. The spinal cord is organized into segments, each corresponding to specific regions of the body: 8 cervical (neck) 12 thoracic (chest) 5 lumbar ...