Question

Dorsal root of the spinal nerve contains-
a. Motor Nerve Fibres
b. Sensory Nerve Fibres
c. Mixed Nerve Fibres
d. No Nerve Fibres

Answer 1

Hint: An afferent nerve is a nerve that conveys data towards the central nervous system (CNS) and all those nerves which can detect or recognize the stimuli. It is a cable-like bunch of the afferent nerve fibers arising from receptors in the peripheral nervous system (PNS). An efferent nerve transports information from the CNS to the PNS, and both types of the nerve are called peripheral nerves.

Complete answer:
Motor nerve fibers are engaged in muscle control, both skeletal and smooth muscle. The cell body of the motor neuron is connected to a single, long axon and some shorter dendrites projecting out of the cell body itself.

Mixed nerve fibers are the nerves that have both afferent and efferent axons, and thus carry out both incoming sensory information and departing muscle commands in the same bundle.

The spinal cord can be split into the dorsal root and the ventral root of the spinal nerves. The dorsal root is composed of sensory nerve fibers whose cell bodies are located in the dorsal root ganglion. The ventral root is formed of the motor neurons. Both the sensory and motor neurons arrive and leave the spinal cord respectively through the intervertebral foramen.

Hence, the correct answer is option (B).

Note: The spinal cord terminates about three-fourths of the way alongside the spine, but a bunch of nerves extends beyond the cord. This cauda equina shifts nerve impulses to and from the legs. Sensory nerves present in the epidermis facilitate touch reception, pain, and thermal sense. The skin is innervated by two kinds of nerve fibers, sensory and autonomic. Nerve fibers covering the skin originate from dorsal root ganglia nerve cell bodies of sensory nerves.