Human Nervous System (For Grade 8)

Human Nervous System

Overview

  • The human nervous system is a complex network that coordinates actions and reactions by transmitting signals between different parts of the body.

  • It consists of two main parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

Central Nervous System (CNS)

  • Components:

    • Brain: The control center of the body, responsible for processing information and making decisions.

    • Spinal Cord: A long bundle of nerves that runs down the back, transmitting signals between the brain and the rest of the body.

  • Functions:

    • Processes sensory information (sight, sound, touch, taste, smell).

    • Controls voluntary movements (walking, talking).

    • Manages involuntary functions (breathing, heartbeat).

Peripheral Nervous System (PNS)

  • Components:

    • Nerves that branch out from the spinal cord and brain to the rest of the body.

  • Divisions:

    • Somatic Nervous System: Controls voluntary movements and transmits sensory information.

    • Autonomic Nervous System: Regulates involuntary functions (heart rate, digestion).

      • Sympathetic Division: Prepares the body for 'fight or flight' response.

      • Parasympathetic Division: Calms the body and conserves energy.

Neurons

  • Definition: The basic building blocks of the nervous system, specialized cells that transmit signals.

  • Structure:

    • Cell Body: Contains the nucleus and organelles.

    • Dendrites: Receive signals from other neurons.

    • Axon: Transmits signals away from the cell body to other neurons or muscles.

Synapse

  • Definition: The junction between two neurons where communication occurs.

  • Process:

    • When a signal reaches the end of an axon, neurotransmitters are released into the synapse.

    • These chemicals bind to receptors on the next neuron, continuing the signal.

Reflex Actions

  • Definition: Automatic responses to stimuli that occur without conscious thought.

  • Example: Pulling your hand away from a hot surface.

  • Process:

    • Sensory neurons detect the stimulus and send signals to the spinal cord.

    • The spinal cord processes the information and sends a