Cells and organisation · GCSE Biology
The brain
Describe the brain and CNS for GCSE Biology: main regions, their roles, and how the brain coordinates responses as part of the nervous system.
Cerebral cortex: conscious thought, memory, language. Cerebellum: balance and coordination. Medulla: breathing and heart rate. Brain + spinal cord = CNS. Brain is the coordinator for complex responses.
The important bits
What you need to know
- 1
The central nervous system (CNS) consists of the brain and spinal cord. It receives information from receptors and coordinates responses via effectors.
- 2
The cerebral cortex is the outer layer of the brain responsible for conscious activities: thinking, memory, language, conscious movement and interpreting sensory information.
- 3
The cerebellum coordinates muscular activity, balance and posture. Damage causes unsteady movement and poor coordination.
- 4
The medulla oblongata controls unconscious actions such as breathing rate, heart rate, blood pressure and swallowing reflexes.
- 5
Sensory neurones carry impulses to the CNS; motor neurones carry impulses from the CNS to muscles and glands. Relay neurones connect pathways inside the CNS.
- 6
The brain acts as a coordinator: it processes information, compares it with memory and experience, and may send motor commands for voluntary responses.
- 7
Reflexes are rapid, automatic responses processed mainly in the spinal cord, though the brain becomes aware afterwards. Complex behaviour involves the cerebral cortex.
- 8
Brain damage can be studied through case studies and scans; different regions have specialised functions, so localised damage produces specific deficits.
Quotations worth analysing
Short evidence. Real method.
“The cerebellum coordinates balance and muscular activity.”
Do not assign conscious thought to the cerebellum. Balance and fine motor control are the mark-scheme phrases.
“The medulla controls unconscious actions such as breathing and heart rate.”
These are vital autonomic functions. Students sometimes confuse medulla with “thinking centre”.
“The CNS is made up of the brain and spinal cord.”
Peripheral nervous system is outside the CNS. Neurones are not the same as the CNS organs themselves.
Go deeper
Map the regions to exam labels
On a sagittal brain diagram, the large folded cortex is at the top and front — thinking, sensation, voluntary movement. The cerebellum sits at the back, below the cortex — coordination. The medulla is at the brain stem, continuous with the spinal cord — autonomic control. If asked “what happens if the cerebellum is damaged”, write poor balance and jerky movement, not paralysis of breathing (that suggests medulla damage). Higher-tier papers may mention the hypothalamus for temperature and water balance; link it to homeostasis if it appears.
Go deeper
Brain as coordinator versus spinal reflex
A voluntary action: receptor → sensory neurone → brain (cortex decides) → motor neurone → muscle. A reflex: receptor → sensory neurone → spinal cord relay → motor neurone → effector, often before the cortex is fully involved. The brain still receives signals, which is why you feel pain after pulling your hand away. Coordination means integrating inputs — for example, reading while walking uses cortex and cerebellum together. Do not write “the brain sends hormones” in the same breath as neurones unless you are comparing nervous and endocrine systems.
Go deeper
Clinical and ethical angles in evaluation
fMRI and CT scans show which areas are active or damaged. Phineas Gage–style case studies illustrate personality change with frontal cortex injury. Treatments for Parkinson’s target motor coordination; brain surgery carries risk to speech or memory. In ethics questions, balance medical benefit against irreversible harm. For GCSE, focus on matching region to function with a consequence of damage — that is the biology mark, not the history of neuroscience.
See the idea in action
A patient has damage to the cerebellum after an accident. Describe likely effects (3 marks). The cerebellum coordinates balance and fine movement. The patient may have difficulty walking steadily, standing upright or performing precise tasks such as catching a ball. Conscious thought and breathing are mainly controlled by other regions, so the patient may still be fully alert.
Exam technique
Turn knowledge into marks
Learn three regions with three functions each. In “coordinator” questions, name the CNS, sensory input, decision or reflex centre, and motor output. Do not put breathing control in the cerebellum.
Common mistakes
Do not give these marks away
- 01
Assigning conscious thought or memory to the cerebellum or medulla.
- 02
Saying the brain is only in the skull with no role for the spinal cord in the CNS.
- 03
Describing all responses as conscious when reflex arcs bypass detailed cortical processing.
Which part of the brain controls balance and coordination?
ACerebral cortex
BCerebellum
CMedulla
DPituitary gland
Show the answer
Cerebellum. The cerebellum coordinates muscular activity and balance. The cortex handles conscious thought; the medulla controls breathing and heart rate.
Quick questions
If this is the bit you searched
What is the CNS?
The central nervous system: the brain and spinal cord, which receive information and coordinate responses.
What does the cerebral cortex do?
It controls conscious activities including thinking, memory, language and voluntary movement.
What is the role of the medulla?
It controls unconscious vital functions such as breathing rate and heart rate.
How does the brain act as a coordinator?
It receives impulses from receptors, processes them, and sends motor commands to effectors for voluntary and learned responses.