This definitions covers Key Definitions within Reflex Arc for GCSE Biology. Topic 3: Reflex Arc It is section 10 of 15 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Key Definitions
Reflex action: A rapid, automatic (involuntary) response to a stimulus that does not require conscious thought and is coordinated by the spinal cord rather than the brain.
Reflex arc: The neural pathway through which a reflex action is coordinated — from receptor through sensory neurone, relay neurone, and motor neurone to effector.
Relay neurone: A nerve cell within the CNS (spinal cord or brain) that connects sensory neurones to motor neurones and coordinates the reflex response.
Synapse: The junction between two neurones across which neurotransmitters diffuse to transmit the signal from one neurone to the next.
Neurotransmitter: A chemical released from the pre-synaptic neurone that diffuses across the synapse and binds to receptor proteins on the post-synaptic neurone to generate a new impulse.
Involuntary response: A response that occurs without conscious control — the person cannot prevent it from happening (e.g. knee-jerk reflex, pupil constriction).
Practice questions for Reflex Arc
Which word best describes a reflex action?
State the correct order of the reflex arc pathway from stimulus to response. Name each component.
Quick recall flashcards
What is the reflex arc pathway?
Stimulus → Receptor → Sensory neurone → Relay neurone (in spinal cord) → Motor neurone → Effector → Response.
What is a reflex action?
A reflex is a rapid, automatic response to a stimulus that does not involve conscious thought. Reflexes protect the body from harm.