Human Nervous System - Peripheral Nervous System (PNS)

The Peripheral Nervous System (PNS) is one of the two main components of the nervous system in bilateral animals, alongside the Central Nervous System (CNS). The PNS includes nerves and ganglia located outside the brain and spinal cord. Its primary role is to connect the CNS to the limbs and organs, acting as a communication network between the brain, spinal cord, and the rest of the body. Unlike the CNS, the PNS is not shielded by the skull, vertebral column, or the blood-brain barrier, making it more vulnerable to toxins.

• Spinal nerves are mixed nerves — they contain both sensory and motor nerve fibres, formed inside the neural canal of the vertebral column.
• Two Roots — Dorsal (posterior) root carries sensory nerve from dorsal root ganglion; Ventral (anterior) root gives out motor nerve.
• Mixed Nerve Formation — Dorsal sensory + Ventral motor nerves together form the mixed spinal nerve, emerging from both sides of the spinal cord through the intervertebral foramen.
• Three Branches — Ramus dorsalis (supplies dorsal skin/muscles); Ramus ventralis (largest; supplies lateral and anterior organs/muscles); Ramus communicans (smallest; T1 to L3; joins sympathetic ganglion).
• The dorsal root ganglion contains sensory neuron cell bodies, while motor neuron cell bodies are located in the spinal cord itself.