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Both types of tracts are made up of neuronal axons that gather into long columns called funiculi, meaning long ropes, which are found inside the ventral, lateral and dorsal parts of the spinal cord.
Ascending tracts are sensory pathways that begin at the spinal cord and stretch all the way up to the cerebral cortex.
There are three types of ascending tracts, dorsal column-medial lemniscus system, spinothalamic (or anterolateral) system, and spinocerebellar system. They are made up of four successively connected neurons.
They further transmit it to the third order neurons found inside the thalamus, and then the fourth order neurons in the cerebral cortex.
While ascending through the spinal cord these tracts cross over to the opposite side of the central nervous system, or CNS, meaning that the left side of the brain receives sensory input from the right side of the body and vice versa.
These crossings are called decussations and they happen at different levels of the CNS for each of these tracts.
Let’s start with the dorsal column-medial lemniscus system which is a sensory pathway that transmits delicate sensations like vibration, proprioception or sensation of the position of bodyparts, two-point discrimination, and touch.
The ascending tracts include the dorsal column-medial lemniscus system, the spinothalamic system, and the spinocerebellar system. These tracts carry sensory information from the periphery, such as pain, touch, and temperature to the brain.
The descending tracts include lateral and anterior corticospinal tracts, the vestibulospinal, the rubrospinal, and the reticulospinal tracts. These tracts carry motor information, such as a motor command to move the arm, from the brain down the spinal cord to the appropriate part of the body.
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