Peripheral Neural System ( PNS ) | MANISH MEVADA

PERIPHERAL NEURAL SYSTEM

The nerves arising from the brain and spinal cord constitute the peripheral neural system.  These nerves are of two types: cranial nerves (12 pairs, nerves originating from brain) and spinal nerves (31 pairs, nerves originating from spinal cord). 

The cranial nerves are: olfactory (sensory), optic (sensory), oculomotor (motor), trochlear (motor), trigeminal (mixed), abducens (motor), facial (mixed), auditory (sensory), glosso pharyngeal (mixed)  , vagus (mixed), spinal accessory (motor) and hypoglossal (motor).  Trigeminal is the largest cranial nerve and is divided into three branches: opthalmic, maxillary and mandibular .

Spinal nerves are classified into 5 groups 8 pairs of cervical nerves : 12 pairs of thoracic nerves ; 5 pairs of lumbar nerves ; 5 pairs of sacral nerves and one pair of coccygeal nerves .

Autonomic Neural System

Autonomic neural system ( ANS ) is a special self governed autofunctioning system of ganglia and peripheral motor nerve fibres ( efferent ) which innervate various organs and glands of the body to stimulate , accelerate , slow down or inhibit their functions without directly consulting the will . ANS is made of two opposing divisions , sympathetic and parasympathetic neural system .

Sympathetic neural system

It is made up of a network of short preganglionic axons that extend to ganglia located near the thoracic and lumbar region of the spinal cord and of long postganglionic neurons extending from the ganglia directly to each target organ . For this reason , the fibres of the sympathetic efferent neurons are also referred to as the thoracolumbar outflow .

Parasympathetic neural system

It is made up of a network of preganglionic axons that synapse with organ - associated ganglia in the immediate vicinity of an organ , located in the cranial and sacral regions of the spinal cord and of short postganglionic neurons extending from the ganglia to the target organ . Thus , the fibres of the parasympathetic efferent neurons are referred to as the craniosacral outflow .

Manish Mevada

M.Sc, M.Phil, B.Ed