itle: Coordination and Control – The Human NervousSystem
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Year: 9
Key Stage: 3
Main Concept: How thebody detects and responds to changes in the environment using
the nervous system.
1. Why Do We Need a Nervous System?
he human body must constantly respond to its environment to stay safe and healthy. The
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nervous system helps us:
● Detect changes in our surroundings
● Send messages quickly
● React quickly and correctly
👉 This process is calledcoordination and control.
2. The Structure of the Nervous System
The nervous system has two main parts:
A. Central Nervous System (CNS)
● Brain and spinal cord
● Processes information and makes decisions
B. Peripheral Nervous System (PNS)
● Nerves linking the body to the CNS
● Carries messages to and from the CNS
3. Key Components and Definitions
● Stimulus: A change in the environment (e.g. heat, light, sound)
● Receptor: Detects the stimulus (e.g. eyes, skin, ears)
● Effector: A muscle or gland that responds to a signal
● Response: The action taken (e.g. moving your hand)
● Neuron: A nerve cell that carries electrical impulses
4. Types of Neurons (Nerve Cells)
Neuron Type
Role
Path
Sensory
arries signals from receptors to the
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CNS
Receptor → CNS
Relay
Transfers signals within the CNS
CNS (Spinal Cord)
Motor
Sends signals from the CNS to effectors
CNS → Muscle/Gland
5. How Do We Respond? (The Pathway)
When your body detects a stimulus, a message travels through the following path:
timulus → Receptor → Sensory Neuron → Relay Neuron → Motor Neuron → Effector
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→ Response
Example:
ou touch a hot surface.
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→ Receptors in your skin detect the heat.
→ Sensory neurons carry the message to your spinal cord.
→ Relay neurons transfer the message.
→ Motor neurons tell your muscle to move.
→ You pull your hand away (response).
6. Reflex Actions – Fast and Automatic
reflex actionis a quick, automatic response to a dangerous stimulus. It protects your
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body from harm.
Reflex Arc Pathway:
Stimulus → Receptor → Sensory Neuron → Relay Neuron → Motor Neuron → Effector
Examples of Reflexes:
● Pulling your hand from a flame
● Blinking when something flies near your eye
● Sneezing when dust enters your nose
Note: Reflexes do not involve the brain directly —they go through the spinal cord.
7. Voluntary vs Reflex Actions
Feature
Controlled by
Voluntary Action
Brain
Reflex Action
Spinal cord
Thinking involved? Yes
No
Speed
Slower
Very fast
Examples
Writing, speaking
Blinking, sneezing
8. The Brain and Its Role
● Thebrainis the control center of the body.
● It interprets sensory information.
● It controls voluntary actions.
● It helps with memory, learning, and emotions.
● Complex reflexes (like catching a falling object) can also involve the brain.
9. Importance of the Nervous System
● Allows quick responses to danger (survival)
● Controls movements, emotions, and decision-making
● Helps different parts of the body communicate
● Enables learning, memory, and coordination
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