Question

what would result if the right lateral spinothalamic tract is severed? multiple choice pain impulses from the left side of the body would be blocked. pain impulses from the right side of the body would be blocked. muscles on the left side of the body would be paralyzed. muscles on the right side of the body would be paralyzed.

Explanation:

The spinothalamic tract (specifically the lateral spinothalamic tract) carries pain and temperature sensations. It has a crossed (decussating) pathway: sensory information from the right side of the body crosses over to the left side of the spinal cord and then ascends, and vice versa. So, if the right lateral spinothalamic tract is severed, the pain impulses coming from the right side of the body (which have crossed to the left side but then the right tract is damaged) would be blocked. The other options are incorrect because the spinothalamic tract is for sensory (pain) not motor (muscle paralysis) functions, and the side of the body corresponding to the tract severance for pain is the same side (right side pain blocked when right tract is severed, due to the crossing of sensory fibers).

Answer:

C. Pain impulses from the right side of the body would be blocked.