Spinal nerves are composed of which fibers?

• A. Purely motor
• B. Mixed nerves (sensory + motor)
• C. Purely sensory
• D. Autonomic nerves

Answer: (B)

Spinal nerves are mixed nerves because they carry both sensory and motor signals. Sensory information from receptors travels into the spinal cord through the dorsal roots, while motor commands leave the spinal cord via the ventral roots. These roots join to form the spinal nerve, which thus contains both types of fibers as it exits the spine. Afterward, the nerve branches into dorsal and ventral rami that innervate different regions of the body. While autonomic fibers can travel with these nerves, the defining feature is the combination of somatic sensory and somatic motor fibers.