This topic summary covers Knowledge Organiser within Nervous System for GCSE Biology. Topic 2: Nervous System It is section 17 of 18 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.

📊 Knowledge Organiser

Key Terms

CNS — brain + spinal cord; coordination centre
Sensory neurone — receptor to CNS
Relay neurone — within CNS; connects sensory to motor
Motor neurone — CNS to effector
Synapse — gap crossed by neurotransmitters
Cerebrum — consciousness, memory, language
Cerebellum — coordination, balance
Medulla — heart rate, breathing rate
Accommodation — lens shape change for focus
Retina — rods (dim light) and cones (colour)

Must-Know Facts

Pathway: stimulus → receptor → sensory → CNS (relay) → motor → effector → response
Nervous: fast, short-lived, precise. Hormonal: slower, long-lasting, widespread
Synapse: release → diffuse → bind → trigger new impulse (RDBT)
Near focus: ciliary muscles contract → ligaments loosen → lens thick
Far focus: ciliary muscles relax → ligaments tight → lens thin
Myopia: concave lens. Hyperopia: convex lens
RPA7: ruler-drop, repeat 5+ times, calculate mean

Common Marks Lost

Writing "nerve" instead of "neurone" (a nerve is a bundle of neurones)
Not naming all three neurone types in pathway questions
Getting ciliary muscle contraction/relaxation wrong for accommodation
Saying reflexes don't involve the CNS (they do — via the spinal cord)
Forgetting to compare BOTH systems in nervous vs hormonal questions

Quick recall flashcards

Name the three types of neurone.

Sensory (receptor → CNS), relay (within CNS), motor (CNS → effector). Remember: SRM — Students Revise Methodically.

Name four types of sensory receptor.

Photoreceptors (light, in eye), thermoreceptors (temperature, in skin), pressure receptors (touch, in skin), chemoreceptors (chemicals, in tongue and nose).

Knowledge Organiser