An impulse that travels inward from a sensory receptor to the spinal cord, then outward to a muscle is called a(n)

Rooting. The dorsal root of spinal nerve (or posterior root of spinal nerve) is one of two "roots" which emerge from the spinal cord. It emerges directly from the spinal cord, and travels to the dorsal root ganglion. The dorsal root transmits sensory information, forming the afferent sensory root of a spinal nerve.

A) early horses is your answer