The PNS is made up of those parts of the Nervous System that are external to to the Central Nervous System, CNS, which is made up of the spinal cord and the brain. The PNS is divided into two branches: the Somatic Nervous System, SoNS and the Autonomic Nervous System, ANS which is in turn divided, having two main branches.
The nerves and ganglia of the PNS send messages to and from the CNS, linking this to the body's limbs and internal organs. These nerves are not very well protected, which leaves them more vulnerable to injury, as can be seen in such conditions as Repetitive Strain Injury, RSI, where the muscles, tendons and also nerves can become damaged through habitual overuse and mis-use.
Such problems as RSI can begin to be addressed in Alexander lessons, when a pupil can learn to use their arms and hands in a more relaxed and free manner whilst adjusting their poise, so that peripheral nerves are no longer irritated and compressed by tension and muscle contraction during everyday activities such as texting and computing.