Axons of the nervous system are described as afferent and efferent according to the direction in which they carry information. Which of the following represents an efferent projection?

a) sensory input to the spinal cord

b) motor output of the spinal cord

c) interneurons in the spinal cord

d) sensory input to the spinal cord, motor output of the spinal cord, interneurons in the spinal cord

The correct option is b) motor output of the spinal cord

Explanation:

Motor neurons, also called afferent neurons, drive impulses from the brain and spinal cord to the receptors (eg, muscles). They are the motor output component of the spinal cord.

The spinal cord is a cord of nerve tissue that runs inside the spine. It conducts the nerve impulses that arrive from the receptors to the brain, and the responses with the motor orders from the brain to the effector organs. Thus, the brain receives the information and can develop an order that modifies the reflex response given by the spinal cord. A spinal nerve has two nerve roots: a motor and a sensory root. The motor root has nerve fibers that carry signals from the spinal cord, to the muscles to stimulate contraction and produce muscle movements, the fibers are efferent as they leave the medulla to the periphery through the anterior roots of the spinal nerves.