This definitions covers Key Definitions within Reflex Arc for GCSE Biology. Topic 3: Reflex Arc It is section 9 of 14 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 9 of 14
Practice
15 questions
Recall
20 flashcards
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).