Synapses and Reflexes

Question 1

What is a synapse?

Answer 1

The connection between two neurones.

Question 2

How is the nerve signal transferred?

Answer 2

By chemicals which diffuse (move) across the gap. These chemicals then set off a new electrical signal in the next neurone.

Question 3

What are reflexes?

Answer 3

Rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain - they can reduce the chances of being injured.

Question 4

Give an example of how a reflex can reduce the chances of being injured.

Answer 4

If someone shines a bright light in your eyes, your pupils automatically get smaller so that less light gets into the eye - this stops it getting damaged.
Or if you can shock, your body releases the hormone adrenaline automatically - it doesn’t wait for you to decide that you’re shocked.

Question 5

What is a reflex arc?

Answer 5

The passage of information in a reflex (from receptor to effector).

Question 6

What do the neurones in reflex arcs go through?

Answer 6

The spinal cord or through an unconscious part of the brain.

Question 7

What happens when a stimulus (e.g. a painful bee sting) is detected by receptors?

Answer 7

1. Impulses are sent along a sensory neurone to a relay neurone in the CNS.
2. When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone.
3. When the impulses reach a synapse between the relay neurone and a motor neurone, the same thing happens. chemicals are released and cause impulses to be sent along the motor neurone.
4. The impulses then travel along the motor neurone to the effector (which is usually a muscle, like in this example).
5. The muscle then contracts and moves your hand away from the bee.
6. Because you don’t have to think about the response it’s quicker than normal responses.