Dorsal Columns and
Anterolateral Tracts




Sensory information is carried up the spinal cord to the brain via two pathways:

The figure to the right shows where the two pathways are found. Axons in the dorsal columns carry fine touch and proprioception up to the brain. Axons in the anterolateral tracts carry pain, temperature and crude touch.





Dorsal Columns

The figure to the right shows a branch of an afferent axon entering the dorsal horn and then continuing up the dorsal column on the same side to the medulla.

In the medulla, the afferent neuron forms a synapse with a second neuron, whose axon crosses over in the medulla to the other side and continues up to the thalamus.

Finally, a third neuron carries the information to the cerebral cortex. The specific region is the somatosensory cortex.


Anterolateral Tracts

The figure to the right shows a branch of an afferent axon entering the dorsal horn. In the dorsal horn, the afferent neuron forms a synapse with a second neuron.

The axon of this second neuron then crosses over at the spinal level and enters the anterolateral tract, where it continues all the way to the thalamus.

Finally, a third neuron carries the information from the thalmus to the cerebral cortex. The specific region is the somatosensory cortex.


Somatosensory Cortex

Sensory information is spatially mapped into the somatosensory cortex in a very organized fashion. This is called somatotopic organization. The information is organized much like the surface of the body, although regions of the body with a large number of afferents have correspondingly larger areas.

QUESTION: A light, vibratory touch is applied to your right finger. Does the sensory information go first to the right or left cerebral cortex?


ANSWER


QUESTION: A painful stimulus is applied to your right finger. Does the sensory information go first to the right or left cerebral cortex?

ANSWER


QUESTION: Does tabes dorsalis cause degeneration in the dorsal columns or the anterolateral tracts? How do you know?

ANSWER