New
New
Year 10
OCR
Higher

The structure and function of a reflex arc

I can describe what a reflex response is and the path a nerve impulse takes through a reflex arc in the nervous system.

New
New
Year 10
OCR
Higher

The structure and function of a reflex arc

I can describe what a reflex response is and the path a nerve impulse takes through a reflex arc in the nervous system.

Lesson details

Key learning points

  1. Reflex responses are fast and involuntary, and are essential to the survival of many organisms.
  2. Reflex responses do not involve a processing centre (e.g. the brain) in the CNS.
  3. In a reflex arc, the nerve impulse travels across a synapse from the sensory neurone to a relay neurone in the CNS.
  4. The nerve impulse travels across a synapse from the relay neurone to a motor neurone in the PNS.
  5. 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.

Allow pupils to sensibly and kindly trigger a reflex response to allow pupils to realise that the response happens before they know about it.
Teacher tip

Equipment

None required.

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
What makes up the central nervous system?
An image in a quiz
brain and motor neurones
relay, and motor neurones
spinal cord and sensory neurones
Correct answer: brain and spinal cord
sensory and relay neurones
Q2.
What does involuntary mean?
Something done with conscious control.
Correct answer: Something done without conscious control.
Something done with and without conscious control.
Q3.
Which of the following is not a feature of nerve cells?
An image in a quiz
dendrons
Correct answer: synapse
axon
myelin sheath
cell body
Q4.
Muscles and glands are known as ...
Correct Answer: effectors, an effector, effector, effectors., effector.
Q5.
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
Q6.
Put these steps in order to show how a synapse works.
An image in a quiz
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.

6 Questions

Q1.
What could cause a reflex reaction?
someone whispering
Correct answer: touching a hot pan
studying
Correct answer: a loud bang
Q2.
What three types of neurone are involved in a reflex arc?
An image in a quiz
Correct answer: relay
synapse
Correct answer: sensory
effector
Correct answer: motor
Q3.
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
Q4.
What are the features of a reflex action?
Correct answer: involunatary
voluntary
Correct answer: quick
slow
Q5.
How does the impulse travel from the end of the relay neurone to the motor neurone?
electrically
Correct answer: chemically
Q6.
To override a reflex action, the brain sends an overriding signal down a neurone.
Correct Answer: motor