Co-ordination & ResponseEdexcel GCSE Biology: Revision notes

Section 1

How does the brain control the body?

Region	Function
Cerebral hemispheres	Memory, personality, conscious thought, learning, intelligence, vision, voluntary movement
Cerebellum	Balance and coordination of muscle movement
Medulla oblongata	Unconscious actions: heart rate, breathing

Key termscerebral hemispherescerebellummedulla oblongata

Common mistake

Do not confuse cerebellum (balance/coordination) with cerebrum (thought, voluntary movement).

Section 2

How do scientists investigate brain function?

CT scanning uses X-rays to show brain structure. PET scanning uses a radioactive tracer to show brain function/activity. Both avoid invasive surgery.

Key termsCT scanningPET scanning

Exam tip

CT = structure; PET = function.

Section 3

Why is treating the nervous system so difficult?

CNS neurones have very limited repair capacity. Spinal injuries can permanently block signals, causing paralysis. Brain tumours are hard to access due to the skull, and surgery risks damaging healthy tissue.

Key termsspinal injurybrain tumour

Section 4

How is information transmitted?

Pathway: sensory receptor → sensory neurone → relay neurone (CNS) → motor neurone → effector.

Axon carries impulses away from cell body; dendron carries impulses towards it; myelin sheath insulates the axon, speeding transmission.

Synapses: impulse triggers neurotransmitter release, which diffuses across the gap and binds receptors on the next neurone.

Key termssensory neuronerelay neuronemotor neuroneaxondendronmyelin sheathsynapseneurotransmitter

Think of it like this

Myelin sheath is like wire insulation — speeds up the signal.

Section 5

Reflex arc

Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response. Bypasses conscious brain processing for speed.

Key termsreflex arceffector

Example

Touching a hot object triggers withdrawal before pain is even registered by the brain.

Section 6

The eye

Structure	Function
Cornea	Refracts light entering the eye
Lens	Changes shape to fine-tune focus
Iris	Controls pupil size/light entering
Rod cells	Low light, black/white
Cone cells	Colour, fine detail, need bright light

Key termscornealensirisrod cellscone cells

Section 7

Eye defects and correction

Defect	Cause	Correction
Cataracts	Cloudy lens	Lens replacement surgery
Long-sightedness	Image focuses behind retina	Convex lens
Short-sightedness	Image focuses in front of retina	Concave lens
Colour blindness	Faulty cone cells	Cannot be corrected

Key termscataractslong-sightednessshort-sightednesscolour blindness

Exam tip

Convex corrects long-sighted; concave corrects short-sighted.

Must Know

Cerebrum = thought/movement; cerebellum = balance; medulla = unconscious actions.
CT = structure; PET = function.
CNS damage hard to treat: limited repair, difficult access.
Impulse pathway with synapses using neurotransmitters.
Reflex arcs bypass conscious processing.
Cornea/lens focus light; rods = dim light; cones = colour.
Convex lens corrects long-sighted; concave corrects short-sighted.

That's the notes covered.

Carry on to the next subtopic.