The peripheral nervous system (PNS) acts as the body's communication network, connecting the central nervous system (CNS—brain and spinal cord) to the rest of the body. Its primary function is two-fold:
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Relaying sensory information: The PNS gathers information from various parts of your body (organs, limbs, skin) and transmits it to the CNS. This allows you to experience sensations like touch, temperature, pain, and pressure. For example, if you touch a hot stove, sensory neurons in your fingers send a message via the PNS to your brain, which then triggers the reflex to pull your hand away.
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Carrying out motor commands: The PNS also carries instructions from the CNS to muscles and glands, enabling movement and controlling bodily functions. This includes both voluntary actions like walking and involuntary actions such as heartbeat regulation and digestion. For example, when you decide to lift your arm, your brain sends a signal through the PNS to the muscles in your arm, causing them to contract.
The PNS is further divided into two main parts:
- Somatic Nervous System: Controls voluntary movements of skeletal muscles.
- Autonomic Nervous System: Regulates involuntary functions like heart rate, digestion, and breathing. The autonomic nervous system is further divided into the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) systems.
The PNS is crucial for maintaining homeostasis and enabling interaction with the environment. Nerves, extending from the CNS, create this extensive communication network. Schwann cells play a vital role in maintaining the PNS by supporting and insulating axons. The PNS functions through reflex arc circuits, controlled by the CNS, with afferent (sensory) and efferent (motor) pathways.
