AQA GCSE Biology (8461) — Homeostasis
How does an organ made of soft tissue control every thought, movement, and breath you take? The human brain is the ultimate control centre for all complex behaviour.
It is entirely composed of billions of interconnected neurones. While the brain manages complex, conscious behaviours, it is important to note that simple reflexes are automatic and rapid, and do not involve the conscious part of the brain.
To understand the brain, you must be able to identify its three main regions and describe their specific functions:
[Insert diagram of the brain clearly labelling the cerebral cortex, cerebellum, and medulla]
Did you know surgeons can map a patient's brain while they are completely awake? Because the brain itself has absolutely no pain receptors, awake surgery is possible and actually helps scientists map brain areas.
A neuroscientist uses three main techniques to map specific physiological functions to distinct regions of the brain:
1. Studying Patients with Brain Damage: When a patient suffers a lesion (damage from a stroke, injury, or tumour), scientists observe the resulting loss of function. For example, if a patient survives an injury to their frontal lobe and their personality changes drastically, scientists can link that specific damaged region to social behaviour and personality.
2. Electrical Stimulation: Scientists can map functions during an invasive procedure (brain surgery) using an electrode.
3. MRI Scanning Techniques: MRI Scanning uses strong magnetic fields and radio waves to produce detailed internal images. It is highly advantageous because it is completely non-invasive and does not use harmful ionising radiation.
To see the brain actually working, neuroscientists use fMRI (Functional MRI). While a patient performs a task (like tapping their finger), fMRI detects real-time changes in blood flow and oxygenation. The active regions of the cerebral cortex and cerebellum will "light up" on the scan due to increased blood flow, directly linking the anatomical area to the physical task.
Why is treating a brain tumour so much more complex and dangerous than removing a tumour from the digestive system? Investigating and treating brain disorders requires balancing extreme medical complexity with difficult ethical questions.
Physical and Biological Challenges:
Risk vs. Benefit and Ethical Considerations: Any procedure carries a high risk of permanent collateral damage, such as a permanent loss of speech or sudden personality changes. Surgeons must always calculate the Risk-Benefit Ratio to decide if removing a life-threatening tumour justifies the risk of permanent disability.
Furthermore, obtaining valid Informed Consent is ethically challenging. Patients with severe cognitive impairment or brain damage may not fully understand the risks of experimental treatments. Ultimately, treating the brain is uniquely challenging because the permanent nature of cellular damage combined with the organ's fragility creates a much higher risk of unpredictable, life-altering side effects compared to other organs.
Students frequently confuse the functions of the cerebrum and the cerebellum. Remember: the CerebRum is for Reasoning (intelligence/consciousness), while the CerebeLLum is for Locomotion (coordination/balance).
Always use the exact phrase "billions of interconnected neurones" when describing the structural composition of the brain, as this is a specific AQA mark scheme requirement.
For Higher Tier questions on brain scanning, ensure you specify that fMRI shows active regions of the brain by detecting increased blood flow, rather than just showing a static structure.
In 6-mark "Discuss" or "Explain" questions about treating brain disorders, examiners expect you to explicitly link a physical property (e.g., the brain is highly delicate) to a practical surgical outcome (e.g., high risk of permanent collateral damage).
Cerebral Cortex (Cerebrum)
The highly folded outer layer of the brain responsible for higher-level functions like consciousness, intelligence, and memory.
Cerebellum
The region at the back of the brain that coordinates muscular activity and maintains balance.
Medulla
The part of the brainstem that controls automatic, involuntary (unconscious) actions like heartbeat and breathing.
Neuroscientist
A scientist who studies the structure and function of the brain and the nervous system.
Lesion
A region in an organ or tissue which has suffered damage through injury or disease.
Invasive Procedure
A medical procedure that requires entry into the body (e.g., cutting through the skull).
Electrode
A specialized conductor used to deliver electrical impulses directly to brain tissue.
MRI Scanning
A non-invasive imaging technique that uses magnetic fields and radio waves to produce detailed images of the brain.
fMRI (Functional MRI)
A type of MRI that measures brain activity in real-time by detecting changes in blood flow.
Blood-Brain Barrier
A semi-permeable border of cells that prevents solutes in the blood from non-selectively crossing into the brain's extracellular fluid.
Risk-Benefit Ratio
An evaluation of whether the potential positive outcomes of a medical procedure are significant enough to justify the possible negative consequences.
Informed Consent
The process by which a patient or research participant is told about the risks and benefits of a procedure and voluntarily agrees to it.
Put your knowledge into practice — try past paper questions for Biology
Cerebral Cortex (Cerebrum)
The highly folded outer layer of the brain responsible for higher-level functions like consciousness, intelligence, and memory.
Cerebellum
The region at the back of the brain that coordinates muscular activity and maintains balance.
Medulla
The part of the brainstem that controls automatic, involuntary (unconscious) actions like heartbeat and breathing.
Neuroscientist
A scientist who studies the structure and function of the brain and the nervous system.
Lesion
A region in an organ or tissue which has suffered damage through injury or disease.
Invasive Procedure
A medical procedure that requires entry into the body (e.g., cutting through the skull).
Electrode
A specialized conductor used to deliver electrical impulses directly to brain tissue.
MRI Scanning
A non-invasive imaging technique that uses magnetic fields and radio waves to produce detailed images of the brain.
fMRI (Functional MRI)
A type of MRI that measures brain activity in real-time by detecting changes in blood flow.
Blood-Brain Barrier
A semi-permeable border of cells that prevents solutes in the blood from non-selectively crossing into the brain's extracellular fluid.
Risk-Benefit Ratio
An evaluation of whether the potential positive outcomes of a medical procedure are significant enough to justify the possible negative consequences.
Informed Consent
The process by which a patient or research participant is told about the risks and benefits of a procedure and voluntarily agrees to it.
