Descending tracts are pathways of neurons that connect the brain to the spinal cord. They are responsible for carrying information from the brain to the spinal cord, allowing for communication between the two. This information includes motor, sensory, and autonomic commands.
The descending tracts are divided into three main categories: medial, lateral and ventral. The medial descending tracts are responsible for controlling voluntary movement. They are composed of corticospinal, corticobulbar, and rubrospinal tracts. The corticospinal tract is the most important of these, as it carries the majority of the motor information from the cerebral cortex to the spinal cord. The corticobulbar tract is a smaller pathway composed of neurons from the motor cortex that innervate cranial nerve nuclei. The rubrospinal tract is composed of neurons from the red nucleus that modulate motor commands from the cerebral cortex.
The lateral descending tracts are composed of the reticulospinal and vestibulospinal tracts. These pathways are responsible for regulating posture and balance, as well as controlling motor commands for the neck and trunk. The reticulospinal tract is derived from neurons of the reticular formation, and it is responsible for controlling the tone and posture of the trunk and neck muscles. The vestibulospinal tract is composed of neurons from the vestibular nuclei, and it is responsible for controlling balance and posture.
The ventral descending tracts are responsible for the transmission of autonomic commands from the brain to the spinal cord. These tracts include the lateral and dorsal columns. The lateral column is composed of neurons from the hypothalamus, and it is responsible for controlling visceral and cardiovascular functions. The dorsal column is composed of neurons from the lateral nucleus of the thalamus, and it is responsible for controlling pain and temperature.
Descending tracts play an important role in the functioning of the nervous system, as they are responsible for carrying information from the brain to the spinal cord. They are divided into three main categories: medial, lateral, and ventral. Each of these categories contains specific tracts that are responsible for controlling different aspects of motor, sensory, and autonomic commands.
References
Brown, T. (2003). Neuroanatomy: An Illustrated Colour Text. Edinburgh: Churchill Livingstone.
Kandel, E.R., Schwartz, J.H., & Jessell, T.M. (2000). Principles of Neural Science (4th ed.). New York: McGraw-Hill.
Purves, D., Augustine, G.J., Fitzpatrick, D., Hall, W.C., LaMantia, A.-S., & White, L.E. (2001). Neuroscience (3rd ed.). Sunderland, MA: Sinauer Associates.