S4.5.2 For the adult
Reflexes
Why do you pull your hand away from a hot pan before you even feel the pain?
What this chapter teaches
A reflex is a quick, automatic, protective response. Its path is short: receptor, sensory neurone, relay neurone, motor neurone, effector. A reaction time is longer because the brain decides. A falling ruler measures it, using the time of a free fall.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why do you move your hand away from a hot pan before you feel the pain?
- What is the difference between a reflex and a decision?
- How can a falling ruler measure how fast you react, and why do we repeat it?
After the chapter, the learner can
- Draw a reflex arc with sensory, relay and motor neurones
- Measure your reaction time with a falling ruler
What they copy into their notebook
A reflex is quick, automatic and protective. Its path is receptor, sensory neurone, relay neurone, motor neurone, effector. The brain is told later. Reaction time is longer, because the brain decides.