The brain (HT): regions, function and the difficulty of treating brain damage
The brain is the master coordination centre of the nervous system. It is made up of billions of interconnected neurones and is divided into specialised regions, each carrying out particular functions. Higher-tier learners need to know three named regions plus how scientists investigate brain function.
Three regions you need to know
- Cerebral cortex — the large, folded outer layer of the cerebrum. It is responsible for consciousness, language, memory, intelligence and behaviour. It is split into left and right hemispheres connected by the corpus callosum.
- Cerebellum — sits below and behind the cerebrum. Coordinates muscle movement, balance and posture. Damage produces jerky, uncoordinated movement.
- Medulla (oblongata) — at the top of the spinal cord. Controls unconscious activities essential for life: heartbeat, breathing rate and blood pressure.
You may also see the hypothalamus mentioned (regulates temperature and water balance) and the pituitary ("master gland") that hangs below it — these are revisited in B5.6 and B5.8.
Methods of investigating the brain
The brain is delicate, encased in skull, and damaging it for research is unethical, so scientists use non-invasive methods.
- Studying patients with brain damage. When a region is damaged (by stroke, accident or tumour), scientists observe what changes in the patient's abilities — and so map function to region. The pioneering example is Phineas Gage, who survived a railway-spike injury and changed personality, suggesting the frontal cortex shapes personality.
- Electrical stimulation of the brain. During neurosurgery, surgeons can stimulate small regions while the patient is awake and ask what they feel/see/move. This shows which areas control which functions.
- MRI scanning. Magnetic resonance imaging gives detailed images of brain structure. fMRI can show which areas become active during specific tasks, by detecting changes in blood flow.
Why is the brain hard to treat?
Even when a problem is identified, treatment is difficult because:
- The brain is very complex — neurones are highly interconnected and not yet fully mapped.
- It is delicate and encased in the skull — surgery risks damage to surrounding tissue and infection.
- Drugs may not cross the blood–brain barrier that protects the brain from many chemicals.
- Many neurones in the CNS cannot regenerate — once destroyed, function may be permanently lost.
This is why neurological conditions like Parkinson's, motor neurone disease and severe head injuries remain so hard to cure.
⚠Common mistakes
- Confusing cerebrum and cerebellum. Cerebrum = the big wrinkled bit (thinking, memory). Cerebellum = the smaller "little brain" at the back (movement coordination).
- Saying the medulla controls all unconscious activity. It controls breathing, heart rate and blood pressure specifically — not, for example, digestion (which is largely autonomic but coordinated elsewhere).
- Thinking MRI shows live thoughts. It shows blood flow / oxygen use, which correlates with activity, not the thoughts themselves.
Links
Connects to B5.1 (homeostasis), B5.2 (the nervous system) and B5.5 (temperature regulation by the hypothalamus).
AI-generated · claude-opus-4-7 · v3-deep-biology