Neuroanatomy - Spinothalamic Tract & Spinal Tectal Tract (USMLE)

In this Neuroanatomy lecture we will be looking at the Anterolateral Tracts of the Spinal Cord for the USMLE. The anterior column tract which is ascending is the Lateral Spinothalamic Tract and the Anterior Spinothalamic Tract located in the anterior portion of the spinal cord. Also you can find the spinotectal. Spinothalamic is responsible for crude touch and temperature while the spinotectal is responsible for Eye reflexes. SPINOTHALAMIC The fibers that activate pain are the free nerve endings. There are a few substances which activate pain, Serotonin, Prostaglandin, Substance P, potassium, Acid. They go through two type of fibers which are the Fast (Ad) fibers and the slow fibers (C) which is responsible for dull aching pain. Fibers go to the Dorsal Root Ganglion. Here a few fibers go down and up and is known as the tract of Lisseaur. One of the axon will continue on that level and synapse at the gray matter of the spinal cord in the area known as substantia gelatoninosa. The second nerve will cross through the spinal cord and goes to the opposite lateral spinothalamic level and then moves up the spinal cord. As the fiber moves up it will be added laterally until it reaches the medulla oblangata. Crude touch moves in the same way hoewver, it goes through the Anterior Spinothalamic Tract rather than the Lateral Spinothalamic Tract. They come together at the Medulla Oblangata to form the Spinal Lemniscus At the level of the pons the fibers Lateral and Anterior Spinothalamic Tract and Spintotectal Tract continue as the Spinal Lemniscus. This goes up to the midbrain where it goes through the spinal tegementum. The superior colliculus is found in the posterior portion of the midbrain and is responsbiel for the movement of the eye. The spinotectal fibers go to the superior colliculus where it continues to the eye. The spinothalamic fibers go up to the thalamus. It goes through the ventroposterior lateral portion of the thalamus along with the Dorsal Column/Medial Lemniscus Tract. After the thalamus the fibers go to the posterior horn of the internal capsule. Then the fibers go to the coronoradiata and the somatosensory portion of the brain. Crude touch can also go to the Cingulate Gyrus and the Insula. Insula is connected to the emotional response. These fibers are also connected to the Reticular System to keep the person awake.