Q.How many pairs of cranial nerves and how many pairs of spinal nerves are present in the human peripheral nervous system?

The peripheral neural system (PNS) covers all nervous tissue outside the CNS — nerves, ganglia, enteric plexuses (which help regulate digestion) and sensory receptors. It includes 12 pairs of cranial nerves (the first two from the forebrain, the remaining ten from the midbrain; all but the Vagus nerve serve the head and face) and 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal), each a mixed nerve formed from a dorsal (sensory, with a ganglion) and a ventral (motor) root. Functionally the PNS splits into the somatic neural system (SNS), which carries voluntary control of skeletal muscle plus some reflex movements, and the autonomic neural system (ANS), which is self-governing, controlled from the hypothalamus, and innervates smooth muscle, cardiac muscle and glands via a chain of preganglionic neuron → autonomic ganglion → postganglionic neuron. The ANS itself divid …