Which nerve fibers are involved in sending motor instructions from the brain to muscles?

Which nerve fibers are involved in sending motor instructions from the brain to muscles?

• A. Motor
• B. Secretory
• C. Sensory
• D. Mixed

Answer: (A)

Motor instructions from the brain to muscles travel via efferent, or motor, fibers. These nerve fibers originate in the brain and spinal cord and carry signals that cause muscle fibers to contract, producing movement. Sensory fibers do the opposite—they carry information from the body back to the brain, such as touch, pain, and proprioception. Secretory fibers mainly control glandular activity and some autonomic targets, not the direct voluntary contraction of skeletal muscles. Some nerves can be mixed, containing both sensory and motor fibers, but the pathways that deliver the movement commands specifically are motor fibers.

Motor instructions from the brain to muscles travel via efferent, or motor, fibers. These nerve fibers originate in the brain and spinal cord and carry signals that cause muscle fibers to contract, producing movement. Sensory fibers do the opposite—they carry information from the body back to the brain, such as touch, pain, and proprioception. Secretory fibers mainly control glandular activity and some autonomic targets, not the direct voluntary contraction of skeletal muscles. Some nerves can be mixed, containing both sensory and motor fibers, but the pathways that deliver the movement commands specifically are motor fibers.