FreeScienceLessons · AQA BiologyThe Nervous System
Key facts
Reflex arc — the correct order
Stimulus → Receptor → Sensory neuron → Relay neuron (in spinal cord) → Motor neuron → Effector → Response
Reflex actions are automatic and rapid — they do not involve conscious thought
The reflex arc bypasses the brain (goes through spinal cord)
Why useful: protects the body from harm faster than conscious thought could
Types of neuron — fill in the table
Type
Role
Sensory neuron
Relay neuron
Motor neuron
Effector
Synapses
Gap between two neurons
Impulse reaches synapse → neurotransmitter released into gap
Neurotransmitter diffuses across → binds to receptors on next neuron
New electrical impulse triggered
Signal travels in one direction only
Exam questions — 3 questions · 10 marks total
⚡ This module includes extended questions (4–6 marks). These are where most marks are lost. Read the hint carefully. Write in linked sentences. The AI will identify exactly which mark scheme points you missed.
3 marksReflex arc orderAQA 8461 style
A student touches a hot object and quickly pulls their hand away. List the components of the reflex arc in the correct order, from stimulus to response. (3 marks)
Hint: There are 7 components. Learn the order: Stimulus → Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector → Response.
+30 XP
1 markSynapse functionAQA 8461 style
How does an electrical impulse cross a synapse?
A The electrical impulse jumps directly across the gap
B A neurotransmitter is released, diffuses across the gap, and triggers a new impulse in the next neuron
C The two neurons fuse together to allow the impulse through
D Ions flow directly from one neuron to the next
6 marksDescribe an investigation into reaction timeAQA Jun 2023 P2 Q2 — real 6-mark question
A student wants to investigate whether drinking coffee affects reaction time. Describe a method the student could use. (6 marks)
Hint: For Level 3 you must describe how results are collected WITH and WITHOUT coffee, plus control variables and repeats.