The peripheral nervous system (PNS) is the network of nerves outside the brain and spinal cord (the central nervous system, CNS). Its main function is to connect the CNS to the limbs, organs, and skin, acting as a relay for transmitting sensory information to the brain and sending motor commands from the brain to muscles and glands. The PNS includes cranial nerves, spinal nerves, neuromuscular junctions, and ganglia. The PNS is divided into two main parts:
- The somatic nervous system, which controls voluntary movements and transmits sensory information from the body to the CNS.
- The autonomic nervous system, which regulates involuntary functions like heartbeat, digestion, and breathing. The autonomic system is further split into the sympathetic ("fight or flight") and parasympathetic ("rest and digest") systems.
Overall, the PNS enables the body to react to the environment, maintain homeostasis, and manage essential life functions outside of conscious control. It also has some ability to regenerate after injury, unlike the CNS. Disorders of the PNS can lead to symptoms like numbness, muscle weakness, and pain. Examples include neuropathies, Guillain-Barre syndrome, and carpal tunnel syndrome.
