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Nervous System

The nervous system is the body’s communication and control network, responsible for detecting changes, processing information, and coordinating responses. It is organised in a hierarchical structure:

  1. Central Nervous System (CNS) – the control centre

    • Includes the brain (thinking, memory, decision-making) and spinal cord (connects brain to body, controls reflexes)

  2. Peripheral Nervous System (PNS) – the communication network

    • All nerves outside the CNS

    • Carries sensory (afferent) information to the CNS

    • Carries motor (efferent) instructions from the CNS to muscles and glands

  3. Autonomic Nervous System (ANS) – part of the PNS

    • Controls involuntary functions (heart, digestion, breathing, glands)

    • Has two divisions:

      • Sympathetic NS – prepares the body for action (“fight or flight”)

      • Parasympathetic NS – calms the body and conserves energy (“rest and digest”)

In short: The nervous system is organised hierarchically, with the CNS at the top controlling and processing, the PNS carrying messages, and the ANS automatically regulating internal functions.