The brain and hormonal control — Edexcel International A Level Biology
Nervous and hormonal coordination, regions of the human brain, brain scanning (CT, MRI, fMRI, PET) and dopamine and serotonin imbalances.
Revision notes
4 short notes, in the order of the specification. Each one in short:
Coordination in animals uses two systems. The nervous system sends rapid electrical impulses along neurones to specific effectors, giving short-lived responses. The endocrine system releases hormones into the blood, which act more slowly on target cells and last longer. The hypothalamus links the two systems.
The human brain has distinct regions. The cerebral hemispheres control conscious thought, voluntary movement and senses; the hypothalamus maintains the internal environment and controls the pituitary gland; the pituitary releases hormones; the cerebellum coordinates movement and balance; and the medulla oblongata controls heart rate and breathing.
CT uses X-rays to build images of brain structure, and MRI uses magnetic fields and radio waves to give detailed soft-tissue images. fMRI detects changes in blood oxygen to map active areas, and PET uses a radioactive tracer to show where the brain uses glucose. They diagnose disease and investigate brain function.
Naturally occurring brain chemicals, such as the neurotransmitters dopamine and serotonin, must be in balance. Loss of dopamine-producing neurones leads to Parkinson’s disease, and low serotonin activity at synapses is linked to depression. Knowing how these synapses work has allowed new drugs to be designed to correct the imbalance.
Exam questions
8 exam-style questions (28 marks), each with its mark scheme.
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Quick check questions
Which region of the brain coordinates movement and balance?
Show answer
The cerebellum.
Which region of the brain controls heart rate and breathing rate?
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The medulla oblongata.
What does fMRI show that MRI alone does not?
Show answer
Which areas of the brain are active, by detecting changes in blood oxygen.
Which neurotransmitter is lacking in Parkinson’s disease?
Show answer
Dopamine.
Frequently asked questions
What is the difference between nervous and hormonal coordination?
Nervous coordination uses electrical impulses along neurones to produce fast, short-lived responses in specific effectors. Hormonal coordination uses chemicals released into the blood, which act more slowly and last longer on any target cells with receptors. The hypothalamus links the two systems by controlling the pituitary gland.
What do the different parts of the brain do?
The cerebral hemispheres control conscious thought, memory and voluntary movement. The hypothalamus regulates temperature, water balance and the pituitary gland. The pituitary secretes hormones. The cerebellum coordinates movement and balance, and the medulla oblongata controls involuntary actions such as heart rate and breathing rate.
What is the difference between MRI and fMRI?
MRI uses a magnetic field and radio waves to make detailed images of brain structure. fMRI uses the same scanner to detect changes in blood oxygen level in the brain over time. Active neurones use more oxygen, so fMRI shows which parts of the brain are working during a task.
How does PET scanning work?
A radioactive tracer, often a glucose analogue, is injected and active parts of the brain take up more of it. The tracer emits positrons, which produce gamma rays that detectors record. A computer makes an image of metabolic activity. It is used to investigate dementia, epilepsy and tumours.
How is dopamine linked to Parkinson’s disease?
Parkinson’s disease occurs when neurones that produce dopamine in a part of the brain controlling movement die. The lack of dopamine at synapses causes tremor, rigidity and slow movement. L-DOPA is used as treatment because it crosses the blood–brain barrier and is converted into dopamine in the brain.
Written and checked against the Edexcel International A Level Biology (YBI11) specification · Updated October 2026