Science: Biology

5.1.2 The Human Nervous System

Exam Board: AQA

The Human Nervous System

What is the purpose of the nervous system:

1. React to surroundings  

2. Coordinate behaviour

There are 2 pathways that you need to understand:

1. Normal Conscious Pathway  

• Stimulus → Receptor → Sensory neuron → Coordinator (brain) → Motor neuron → Effector → Response

    2. Reflex Arc (Automatic & Fast)  

• Stimulus → Receptor → Sensory neuron → Synapse → Relay neuron (in spinal cord) → Synapse → Motor neuron → Effector → Response

• Skips brain → instant reaction (e.g., hand from flame)

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(Make diagrams)

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A synapse is a tiny gap between different neurons. A chemical neurotransmitter carries the signal across the gap.

> Required Practical 7: Measure reaction time (ruler drop test)