Reflex Arcs

This lesson covers reflex actions and reflex arcs as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the reflex arc pathway, explain why reflexes are important and describe examples of reflex actions.

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What Is a Reflex Action?

A reflex action is a rapid, automatic response to a stimulus that does not involve conscious thought. Reflexes are:

• Fast — they happen in a fraction of a second.
• Automatic — they do not require a decision from the brain.
• Protective — they help protect the body from harm.

Examples of reflex actions:

Stimulus	Reflex Response	Purpose
Touching a hot object	Hand pulled away	Prevents burns
Bright light shining in eye	Pupil constricts	Protects retina from damage
Object flying towards face	Eyes blink	Protects eyes
Food at the back of throat	Swallowing	Prevents choking
Stepping on a sharp object	Foot lifted	Prevents injury
Tapping below the kneecap	Knee jerks forward	Tests spinal cord function (knee-jerk reflex)