Within the spinal cord, there are several different tracts. Grossly, they are divided into ascending and descending tracts. On the cross-section of the spinal cord, these tracts make up the white matter, named because of the whitish colour that the myelin around the axon gives. The grey matter is located centrally, comprising the ventral and dorsal horns. The ascending pathways are responsible for transporting information from the body These are sensory tracts. We will colour these tracts in blue and starting from the posterior column, also known as the dorsal column, we have the fasciculus cuneatus and fasciculus gracilis. These are responsible for fine touch or tactile sensation, vibration and proprioception. Fasciculus gracilis lies medially to fasciculus cuneatus and the difference between the pathways is that signals from the lower limb generally below T6 travel in the fasciculus gracilis while signals from the upper limb generally T6 and above travel in the fasciculus cuneatus. You can remember this with the L in gracilis reminding you of legs or lower limbs. These tracts run ipsilaterally through the spinal cord and decussate in the medulla of the brain stem. Therefore, a spinal cord injury will lead to loss of ipsilateral fine touch, vibration and proprioceptive sensation. Next up we have the anterior spinothalamic and the lateral spinothalamic pathways. The anterior spinothalamic tract is responsible for crude touch and pressure, while the lateral spinothalamic tract is responsible for pain and temperature. In contrast to the dorsal column tracts, the anterolateral pathways decussate within the spinal cord and then travel up to the brain. This means that a lesion of the spinal cord will generally cause a contralateral loss of crude touch, pressure, pain and temperature sensation. This is not a 100% rule however as nerves entering the anterolateral pathways typically ascend one or two vertebral levels before they cross to the other side. Both the dorsal column and anterolateral pathways are involved in transmitting conscious sensation. The next tracts, the anterior and posterior spinocerebellar tracts and the spinolivary tract instead carry unconscious sensation specifically. They are involved in transmitting proprioceptive information of the lower limbs up to the cerebellum. In addition to these pathways, there are the cuneocerebellar and rostral spinocerebellar tracts that exist more superiorly. These carry the proprioceptive signals of the upper limbs and neck back to the cerebellum. Now we'll take a look at the descending pathways, the pathways responsible for muscle movement. First we have the pyramidal tracts. which are the anterior and lateral corticospinal tracts. These carry signals down from the brain involved with voluntary movement of the limbs. The lateral corticospinal tract is comprised of decussated fibers, meaning if they originated from neurons in the left cerebral cortex, they will travel on the right side of the spinal cord. In contrast, the anterior corticospinal tract fibers do not decussate until they reach the spinal cord level which they innervate. This then leaves the four extrapyramidal tracts. First is the rubrospinal tract, providing contralateral innervation involved in fine motor control. Then we have the reticular spinal tracts, which include medial reticular spinal tract, involved in facilitation of voluntary muscle contraction and increasing muscle tone, as well as the lateral reticular spinal tract, which inhibits voluntary movement, reduces muscle tone, and plays a role in automatic breathing. Next is the vestibular spinal tract, which helps control balance and posture, and the fourth tract is then the tectospinal tract, which is involved in the coordination of head movements with vision.