Question

A spinal nerve takes nerves impulse:
A. to the CNS
B. away from the CNS
C. Both to and away from the CNS
D. Only inside the CNS

Answer 1

Hint: The human neural system is grouped into two parts that are the central neural system and peripheral neural system. The CNS is only the site of information whereas the PNS comprise all the nerves that carry the information away and to the CNS (brain and spinal cord).

Complete answer:
The PNS only comprises nerves which connect all the nerves from the CNS that is to the brain and spinal cord. The PNS is divided into two divisions - automatic neural system and somatic neural system. The nerve fibres of the PNS are of afferent type (sensory nerve) and efferent type (motor). The PNS has 12 pairs of cranial nerves and their branches and 31 pairs of spinal nerves and their branches. In PNS, the cranial nerves take the impulses to and from the brain. While spinal nerves take the impulse to and from the spinal cord.
Spinal nerves- It is a mixed nerve, which transmits motor, sensory and automatic signals between the body to the spinal cord. Each nerve in spinal nerves has a dorsal and ventral root, which is sensory and motor type respectively.

Therefore the correct answer is option C that is both to and away from the CNS.

Additional information: In the spinal nerve, each nerve has several sensory and motor neurons. Some of them are somatic neurons (conduct impulses to or from somatic structures) while some of them are visceral (conduct impulses to or from visceral structures). Therefore the spinal nerves are divided into
> Somatic efferent
> Somatic afferent
> Visceral efferent
> Visceral afferent

Note: Brief definition of
> Somatic neural system- relays impulses from CNS to skeletal muscle.
> Automatic neural system- transmit impulses from CNS to the involuntary organs
> Afferent nerve fibre- carries impulses from organs/tissues to CNS
> Efferent nerve fibre- transmits impulses from CNS to organs/tissue.