The structure and function of a reflex arc | Biology | Quizalize & Oak National Academy

Starter quiz

What makes up the central nervous system?

brain and motor neurones

relay, and motor neurones

spinal cord and sensory neurones

brain and spinal cord ✓

sensory and relay neurones
What does involuntary mean?

Something done with conscious control.

Something done without conscious control. ✓

Something done with and without conscious control.
Which of the following is not a feature of nerve cells?

dendrons

synapse ✓

axon

myelin sheath

cell body
Muscles and glands are known as ...

'effectors' ✓
Put these steps in order to show how a nervous impulse travels to the brain.

1

⇔

sensory receptor

2

⇔

sensory neurone

3

⇔

relay neurone

4

⇔

brain
Put these steps in order to show how a synapse works.

1

⇔

The nerve signal arrives at the end of the first neurone.

2

⇔

The vesicles release neurotransmitters into the synaptic gap.

3

⇔

The neurotransmitters diffuse across the synaptic gap.

4

⇔

The neurotransmitters bind to a receptor on the second neurone.

Exit quiz

What could cause a reflex reaction?

someone whispering

touching a hot pan ✓

studying

a loud bang ✓
What three types of neurone are involved in a reflex arc?

relay ✓

synapse

sensory ✓

effector

motor ✓
Put these stages of a reflex arc in the right order.

1

⇔

sensory receptor

2

⇔

sensory neurone

3

⇔

relay neurone

4

⇔

motor neurone

5

⇔

effector
What are the features of a reflex action?

involunatary ✓

voluntary

quick ✓

slow
How does the impulse travel from the end of the relay neurone to the motor neurone?

electrically

chemically ✓
To override a reflex action, the brain sends an overriding signal down a ______ neurone.

'motor' ✓

Worksheet

Loading worksheet ...

Presentation

Loading presentation ...

Video

Lesson Details

Key learning points

Reflex responses are fast and involuntary, and are essential to the survival of many organisms.
Reflex responses do not involve a processing centre (e.g. the brain) in the CNS.
In a reflex arc, the nerve impulse travels across a synapse from the sensory neurone to a relay neurone in the CNS.
The nerve impulse travels across a synapse from the relay neurone to a motor neurone in the PNS.
Sometimes the brain can modify (e.g. stop) a reflex response via a neurone to the motor neurone of the reflex arc.

Common misconception

What constitutes a reflex response, and how they are generated in the body is often confused and muddled, leading to an incorrect mix between a standard neural pathway and the reflex pathway.

The reflex pathway is clearly stated and explained, and it is compared to the standard neural pathway. Plenty of examples of reflexes are given, including those that occur in other organisms, and there is a quick practical to try too.

Keywords

Involuntary - Something that occurs without you realising or controlling it.
Reflex response - An involuntary, fast neural response to a situation.
Reflex arc - The fixed neural pathway that controls the reflex response.
Relay neurone - An intermediate neurone that sits within the central nervous system.