The Brain & Nervous System

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CognitoThe nervous system and brain

CognitoReflex arcs

Key facts & methods

Nervous system structure

Central Nervous System (CNS): brain + spinal cord. Coordinates responses.
Peripheral Nervous System (PNS): all nerves outside the CNS.
Sensory neurones: carry impulses FROM receptors TO CNS.
Relay neurones: within the CNS, connecting sensory to motor neurones.
Motor neurones: carry impulses FROM CNS TO effectors (muscles/glands).
Impulses cross synapses using neurotransmitters (chemical signals).

Reflex arcs

Reflexes are automatic, rapid responses that do not involve conscious thought.
Reflex arc pathway: receptor → sensory neurone → relay neurone (spinal cord) → motor neurone → effector.
Reflexes bypass the brain — this makes them faster.
Examples: knee jerk, pupil dilation, withdrawing hand from hot object.
Reflex responses protect the body from harm without waiting for conscious decision.

Brain structure and function

Cerebral cortex: outer layer — consciousness, intelligence, language, memory.
Cerebellum: coordinates movement and balance.
Medulla oblongata: controls unconscious processes — breathing rate, heart rate.
Hypothalamus: regulates body temperature, water balance. Links nervous and hormonal systems.

Studying the brain (Higher)

Brain damage cases: patients with injuries reveal which area controls which function (e.g. Phineas Gage → frontal lobe and personality).
Electrical stimulation: stimulating regions of the brain and observing responses.
MRI scans: show which brain regions are active during specific tasks (non-invasive).
Difficulty: brain is extremely complex; treating brain disease is difficult because drugs may not cross the blood-brain barrier; surgery risks damaging healthy tissue.

Exam questions — 5 questions · 11 marks · AQA 8461 style

1 markReflex arc orderAQA 8461 style

A student touches a hot plate and quickly pulls their hand away. What is the correct order of the reflex arc?

A Brain → spinal cord → muscle → hand pulls away

B Receptor → sensory neurone → relay neurone → motor neurone → effector

C Motor neurone → relay neurone → sensory neurone → receptor

D Receptor → motor neurone → brain → effector

1 markBrain regionAQA 8461 style

Which part of the brain controls heart rate and breathing rate?

A Cerebral cortex

B Cerebellum

C Medulla oblongata

D Hypothalamus

3 marksWhy reflexes are fastAQA 8461 P1 style

Explain why reflex responses are faster than voluntary responses. (3 marks)

Hint: Focus on: the pathway length (bypasses brain), the fact it's automatic (no conscious thought), and how this reduces time.

+30 XP

4 marksMethods for studying the brainAQA 8461 Higher style

Describe TWO methods scientists use to study the brain and explain one difficulty in treating brain disorders. (4 marks)

Hint: Two methods with brief explanation each. For difficulty: think about drug treatment (blood-brain barrier) or surgical treatment (complexity/risk).

+40 XP

1 markSynapse functionAQA 8461 style

How do nerve impulses cross a synapse?

A Electrical impulses jump directly from one neurone to the next

B Neurotransmitter chemicals are released from one neurone, diffuse across the gap, and bind to receptors on the next neurone

C The neurones physically connect and fuse at the synapse

D Ion channels in the neurone membrane directly connect to the next neurone

The Brain & Nervous System

Nervous system structure

Reflex arcs

Brain structure and function

Studying the brain (Higher)

Module complete! 🎉