Edexcel A Level Biology A (Salters-Nuffield)
Edexcel A Level Biology A Topic 8: Grey Matter Exam Questions
Free Edexcel A Level Biology A exam questions for Topic 8: Grey Matter, with a mark scheme for every pack. Covers neurones, action potentials, synapses, vision and rhodopsin, plant responses, brain structure and imaging, learning, habituation, drugs and genetic modification.
Topic 8: Grey Matter exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel A Level Biology A Topic 8: Grey Matter
Topic 8 of Edexcel A Level Biology A (Salters-Nuffield) explores the nervous system. You learn the structure of neurones, how resting and action potentials are generated and how impulses are transmitted across synapses. Vision is studied through the pupil reflex and how light breaks down rhodopsin in rod cells, and plant responses through phytochrome and auxin. You then study brain regions, imaging techniques such as CT, MRI and fMRI, the development of vision during critical periods, habituation and learning. The topic ends with drugs acting at synapses and the use of genetically modified organisms to produce drugs. It is assessed in Paper 2 and Paper 3.
What you need to know
- Neurones and impulses Sensory, relay and motor neurones carry impulses. The resting potential is about -70 mV; depolarisation occurs as Na+ channels open, then K+ channels open to repolarise. Myelination allows saltatory conduction.
- Synapses Acetylcholine or other neurotransmitters are released by exocytosis when Ca2+ enters the presynaptic knob; they bind receptors on the postsynaptic membrane. Excitatory and inhibitory synapses allow summation.
- Vision In rod cells, light causes rhodopsin to break into retinal and opsin, which closes Na+ channels, hyperpolarises the cell and stops release of inhibitory neurotransmitter, so bipolar cells depolarise.
- Plant responses Phytochrome exists as Pr and Pfr and controls flowering and germination. Auxin (IAA) causes cell elongation in phototropism.
- Brain and learning Know the roles of the cerebral hemispheres, hypothalamus, cerebellum and medulla oblongata. Imaging uses CT, MRI and fMRI. Hubel and Wiesel's work showed a critical period for visual development. Habituation is a reduced response to a repeated harmless stimulus.
- Drugs and genetic modification Drugs such as L-dopa (Parkinson's disease) and MDMA (serotonin) act at synapses. Genetically modified organisms can produce drugs; this raises ethical and risk issues.
Common mistakes in Topic 8: Grey Matter
- Saying light causes rod cells to depolarise; light causes hyperpolarisation of rod cells.
- Writing that habituation is damage to sensory receptors; it is a learned reduction in response at the synapse.
- Confusing fMRI with MRI; fMRI shows brain activity by detecting changes in oxygenated blood flow.
- Stating that Pr is the active form of phytochrome; Pfr is the biologically active form.
- Forgetting that ethical arguments about animal experiments in vision research must be balanced against medical benefits.
Try three Topic 8: Grey Matter exam-style questions
1. An impulse travels 0.12 m along a neurone in 4 ms. Calculate the speed of conduction. (2 marks)
Show the mark scheme answer
0.12 / 0.004; = 30 m s-1.
2. Explain how light striking a rod cell leads to an impulse in a bipolar cell. (4 marks)
Show the mark scheme answer
Light breaks rhodopsin into retinal and opsin; Na+ channels close so rod cell hyperpolarises; rod cell stops releasing inhibitory neurotransmitter; bipolar cell depolarises and an impulse passes to the ganglion cell.
3. Explain how a lack of dopamine in Parkinson's disease can be treated with L-dopa. (3 marks)
Show the mark scheme answer
L-dopa is a precursor of dopamine; it crosses the blood-brain barrier; it is converted into dopamine in the brain, increasing transmission at dopamine synapses.
Topic 8: Grey Matter FAQs
What does Edexcel A Level Biology A Topic 8: Grey Matter cover?
It covers neurones, action potentials and synapses, vision, plant responses to light, brain structure and imaging, learning and habituation, drugs and genetically modified organisms.
Which paper is Topic 8 examined in?
At A Level, Topic 8 is assessed in Paper 2 and can also appear in Paper 3, which covers all topics and practical skills.
Which core practical is linked to Topic 8?
You should know how to investigate habituation to a stimulus in an invertebrate such as a snail, including how to control variables and treat the animal ethically.
