ICSE 7 Biology Nervous Short

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Table of Contents

    ⚡ Quick Revision: The Control Center

    The nervous system coordinates and controls all body activities by receiving, processing, and responding to stimuli from the environment.

    Structural Unit

    Neuron: The basic structural and functional unit of the nervous system. It consists of a Cyton (cell body), Dendrites (receivers), and an Axon (transmitter).

    Broad Classification

    • 1 Central Nervous System (CNS): Includes the Brain and the Spinal Cord. It is the main processing center.
    • 2 Peripheral Nervous System (PNS): Consists of all the Nerves that connect the CNS to the rest of the body.
    [Diagram: Division of the Human Nervous System]
    Labeled Figure: System Architecture

    ⚡ Quick Revision: The Human Brain

    Anatomy Overview

    The brain is protected by the Skull (Cranium) and three protective membranes called Meninges. It is divided into three main parts.

    Three Major Parts of the Brain

    Part Location Primary Functions
    Cerebrum Largest part (Forebrain). Intelligence, memory, logic, and voluntary actions.
    Cerebellum Below the Cerebrum (Hindbrain). Maintains Body Balance and coordinates muscular movement.
    Medulla Oblongata Base of the brain. Controls involuntary actions like heartbeat and breathing.
    💡 Exam Tip:

    The Cerebrum is highly folded to increase the surface area for more neurons, which is why humans have higher intelligence compared to other animals.

    Labeled Figure: Major Brain Regions

    ⚡ Quick Revision: Spinal Cord & Reflex Actions

    The spinal cord is the extension of the Medulla Oblongata. It acts as a bridge between the brain and the body and handles emergency "shortcuts" known as Reflexes.

    What is a Reflex Action?

    An automatic, sudden, and involuntary response to a stimulus that does not involve the conscious brain (e.g., withdrawing your hand from a hot plate).

    The Reflex Arc (The Path):
    1. Receptor: Sense organ receives the stimulus.
    2. Sensory Neuron: Carries the message to the Spinal Cord.
    3. Association Neuron: Processes the message in the Spinal Cord.
    4. Motor Neuron: Carries the command to the muscle.
    5. Effector: Muscle responds (contracts).

    Types of Nerves

    • ✔ Sensory Nerves: Carry impulses from sense organs to the brain/spinal cord.
    • ✔ Motor Nerves: Carry commands from the brain/spinal cord to muscles/glands.
    • ✔ Mixed Nerves: Contain both sensory and motor fibers.
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    [Diagram: The Reflex Arc Mechanism]
    Labeled Figure: Emergency Response Loop
    ✅ Chapter "Nervous System" Complete. Ready for the next unit?
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