10.4 The Brain

A free GCSE Biology lesson for AQA (8461) from OBA School: the cerebral cortex, cerebellum and medulla, how scientists study the brain, and why brain damage is hard to treat. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe the brain as a complex organ made of billions of interconnected neurones
• Identify the cerebral cortex, cerebellum and medulla and give their functions
• Describe how scientists have mapped regions of the brain to functions
• Evaluate the benefits and risks of procedures on the brain and explain why treatment is difficult

Key words

• Cerebral cortex: The folded outer layer of the brain. Responsible for consciousness, intelligence, memory and language.
• Cerebellum: The region at the back and bottom of the brain that coordinates muscular activity and balance.
• Medulla: The region at the base of the brain that controls unconscious activities such as heartbeat and breathing.
• MRI scan: Magnetic resonance imaging: makes detailed images of soft tissue, including the brain, without X-rays.
• Neurosurgery: Surgery on the brain or nervous system.

Regions of the brain

The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.

• Cerebral cortex; Main functions Consciousness, intelligence, memory, language. Different areas handle vision, hearing, movement and thinking.
• Cerebellum; Main functions Coordinates muscular activity: balance, posture and smooth, accurate movements.
• Medulla; Main functions Controls unconscious activities: heart rate, breathing rate, swallowing, sneezing.

Worked example: which region?

After a fall, a man can talk and remember normally, but he walks unsteadily and cannot touch his nose with his eyes shut. Which region is most likely to be damaged?
Talking and memory (cortex) are fine. Balance and coordination are affected.

Answer: The cerebellum

How scientists study the brain

Neuroscientists have mapped regions of the brain to particular functions in three main ways:

• Studying patients with brain damage; How it works Link a damaged area (after a stroke or injury) to the ability that has been lost; Limitations Damage is rarely in one neat area; cannot be planned
• Electrically stimulating the brain; How it works During surgery, small currents applied to areas; the patient reports what they feel or a muscle moves; Limitations Only possible during brain surgery; invasive
• MRI scans (including functional MRI); How it works Show which areas are most active while a person does a task, e.g. reads or listens to music; Limitations Expensive; some people cannot have scans (metal implants)

Doctors also use CT scans (X-ray images) and PET scans (which use a radioactive tracer to show active areas) to find tumours and damage.

Exam tip: the brain itself has no pain receptors, so some brain surgery is done with the patient awake. This lets surgeons check which areas control speech or movement before they cut.

Why the brain is hard to treat

• The brain is very complex and delicate, and protected by the skull, so it is hard to reach.
• Damage to one area can affect many functions, and it is hard to tell exactly which area is involved.
• Many drugs cannot pass from the blood into brain tissue (the blood–brain barrier).
• Neurones do not repair or replace themselves easily, so damage is often permanent.
• Surgery risks infection, bleeding, and damage to healthy tissue, which could affect memory, movement or speech.

Worked example: weighing up surgery

A study follows 160 patients after surgery for a brain tumour. 128 return to normal daily life; 8 have lasting speech problems.
Percentage returning to normal life = 128 ÷ 160 × 100 = 80%.
Percentage with speech problems = 8 ÷ 160 × 100 = 5%.

Answer: 80% benefit, 5% lasting harm: the patient must weigh these risks

Common mistakes

• Mixing up cerebellum and cerebral cortex. Cerebellum = coordination and balance; cortex = thinking, memory, language.
• Saying the medulla controls conscious actions. It controls unconscious ones like breathing and heartbeat.
• Thinking MRI uses X-rays. MRI uses strong magnetic fields and radio waves; CT uses X-rays.
• Saying brain damage is easy to treat with drugs. Many drugs cannot reach brain tissue.

Revision questions

Try these, then check your answers below each one.

Question 1. A patient can think and talk normally but cannot walk steadily. Which region is most likely damaged? (Choose from: Spinal cord, Cerebral cortex, Cerebellum, Medulla.)

Answer: Cerebellum

Working: The cerebellum coordinates muscular activity and balance.

Question 2. Which region of the brain controls unconscious activities such as breathing?

Answer: medulla

Working: The medulla controls unconscious activities such as heartbeat and breathing.

Question 3. True or false? An MRI scan uses X-rays to make images of the brain.

Answer: False

Working: MRI uses strong magnetic fields and radio waves. CT scans use X-rays.

Related lessons

• Previous lesson: 10.3 Reflex Actions
• Next lesson: 10.5 The Eye
• In this chapter: 10.1 Principles of Homeostasis
• In this chapter: 10.2 The Structure and Function of the Human Nervous System
• In this chapter: 10.6 Common Problems of the Eye

Continue in the full course

This lesson is section 10.4 (AGCBH1004) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.