Which of the following is a characteristic of both spinal and cranial nerves?
(a)-they are pure sensory.
(b)-they are formed from the fusion of anterior and posterior roots.
(c)-they are predominantly motor.
(d)-they contain bundles of axons.

The correct answer is option - D. they contain bundles of axons.

Explanation:

Spinal nerves are is neuron that transfer motor, autonomic, and sensory signals in between the spinal cord and body. There are approximately 31 pairs of spinal nerves present in the human body on each side of the vertebra. These nerves contain numerous bundles of axons that help in sending the signals.

The cranial nerves are made up of 12 pairs of nerves that originate from the nervous tissue of the brain. They must enter or exit through an opening in the skull to the cranium. These nerves have bundles of axons that help in the different function by assisting the carrying the signals to target sites such as facial expression and many more.

Thus, the correct answer is - D. they contain bundles of axons.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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