Peripheral Nervous System

Peripheral nervous system (PNS)

The peripheral nervous system (PNS) consists of all the nerves connecting the body to the brain and spinal cord. It is divided into two main parts: the voluntary (somatic) nervous system and the involuntary (autonomic) nervous system. The somatic system includes sensory and motor neurones that control actions under conscious control, such as moving muscles during physical activities. In contrast, the autonomic system manages unconscious bodily functions like heartbeat, digestion, and sweating, and it is further subdivided into the sympathetic and parasympathetic nervous systems. The sympathetic system generally stimulates body responses during stress (e.g., increased heartbeat, dilated pupils), while the parasympathetic system calms the body after such stimulation (e.g., slowing the heartbeat, constricting pupils).

Additionally, the PNS includes cranial nerves that originate from the brain and control sensory and motor functions in the head, and spinal nerves that arise in pairs from the spinal cord through the vertebrae. Each spinal nerve has a dorsal root (sensory) and a ventral root (motor), which merge before exiting the vertebrae. Overall, the PNS plays a vital role in linking the central nervous system to the rest of the body, enabling both voluntary actions and automatic physiological responses.