4.5.2.1 The human nervous system

How does the nervous system allow us to react to our surroundings?

Receptor cells convert a stimulus into an electrical impulse, which travels along cells called sensory neurons to the central nervous system. The information is then processed and coordinated, resulting in an electrical impulse being sent along motor neurones to effectors. The effectors carry out the response

What are reflexes?

Automatic responses which take place before you have time to think

Why are reflexes important?

They prevent the individual from getting hurt

How does information travel?

Down a pathway called a reflex arc, which allows vital responses to take place quickly

Why is the reflex arc different to the usual response to a stimulus?

The impulse doesn’t pass through the conscious areas of the brain

How does the reflex arc work?

A stimulus is detected by receptors and impulses are sent along a sensory neuron. In the CNS the impulse passes to a relay neurone and then sent along a motor neuron. The impulse reaches an effector, resulting in the appropriate response

What are examples of reflex arcs?

Pupils getting smaller to avoid damage from bright lights, moving your hand from a hot surface to prevent damage

What are synapses?

The gaps between two neurons

How do impulses pass through neurons?

When the impulse reaches the end of the first neuron, a chemical is released into the synapse and this chemical diffuses across the synapse. When this chemical reaches the second neuron, it triggers the impulse to begin again in the next neuron

What is reaction time?

How long it takes you to respond to a stimulus