Final answer:
Nerves composed of both sensory and motor fibers allowing conduction in both directions are known as mixed nerves. Spinal nerves are an example of mixed nerves, containing both sensory neurons in dorsal root ganglia and motor neurons in the ventral gray matter of the spinal cord.
Step-by-step explanation:
Nerves that are composed of both sensory fibers and motor fibers, allowing conduction in both directions, are known as mixed nerves. These nerves have the ability to transmit signals to and from the central nervous system. Sensory fibers carry information to the brain and spinal cord, while motor fibers convey signals from the central nervous system to muscles and glands. The spinal nerves are an example of mixed nerves and contain both sensory and motor axons. Sensory neurons have their cell bodies in the dorsal root ganglia and enter the spinal cord through the dorsal nerve root. Motor neurons, which stimulate skeletal muscles, are found in the ventral portion of the spinal cord's gray matter and send signals through the ventral root.
All spinal nerves are mixed nerves, including sensory neurons present in dorsal root ganglia and motor neurons originating from the anterior horn of the spinal cord. These nerves manage both afferent (sensory) and efferent (motor) functions, making them essential for the peripheral nervous system. Notably, the thoracic spinal nerves directly give rise to intercostal nerves without forming plexuses, but they still remain mixed nerves.