An impulse that travels inward from a sensory receptor to the spinal cord, then outward to a muscle is called a(n) a. inhibitory potential b. excitatory potential c. sensory-motor arc d. reflex arc

The answer is D. So as to take the shortest time to react to stimuli, most sensory neurons are looped through the spinal cord to motor neurons. Following a reflex action, the signal is later passed to the brain, from the spinal cord, for the signal to be analyzed. A reflex arc is divided into somatic and autonomic reflex arcs. The former is connected to outer muscles while the later to inner organs.