Final answer:
The Babinski sign in an adult suggests a lesion or disorder of the corticospinal tract, which originates in the motor cortex, decussates in the medulla, and travels down the spinal cord to interact with lower motor neurons.
Step-by-step explanation:
If an adult displays the Babinski sign, it may indicate that there is a problem with the corticospinal tract which is part of the central nervous system that controls movement. The pathway of the tract begins in the motor cortex of the brain, descends into the brainstem, and crosses over (or decussates) to the opposite side of the body in the medulla oblongata.
The tract then travels down the spinal cord in the lateral column, where it synapses with lower motor neurons in the anterior horn of the spinal cord, which then carry the motor impulses to the muscles of the body. Normally, the corticospinal tract suppresses the reflex that leads to the Babinski sign, so its presence in an adult can indicate a neurological disorder or a lesion to the corticospinal tract.