Key term
OCR GCSE Combined Science Biology J250
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesEnzyme action, and investigating enzymesCellular respiration as an exothermic processAerobic and anaerobic respiration comparedSynthesis and breakdown of carbohydrates, proteins and lipidsPhotosynthesis: producers and the processPhotosynthesis as endothermic, and investigating itLimiting factors in photosynthesis
Community Level Systems
Genes, Inheritance and Selection
Topic overviewGenetic terms, and the genomeGenome, environment and mutationsHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination and characteristics controlled by many genesVariation within a population, and classificationNatural selection and evolutionEvidence for evolution from fossils and antibiotic resistance
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, monitoring conservation and ecotourismSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesWhite blood cells, antibodies and plateletsNon-specific defences and the immune systemVaccines, medicines and aseptic techniqueDeveloping new medicines, and non-communicable diseaseTreating cardiovascular disease, and lifestyle factorsCancer, and the use of stem cells in medicineGene technology in medicine, and the human genome
Organism Level Systems
Scaling Up
Topic overviewDiffusion, osmosis and active transportMitosis, the cell cycle and cell differentiationStem cells in animals and meristems in plantsSurface area to volume ratio and exchange surfacesThe circulatory system, the heart and blood vesselsRed blood cells and plasmaRoot hair cells, transpiration and translocationXylem and phloemFactors affecting water uptake, and the potometer
Organism Level Systems
The reflex arc
- 3 things to know
- Paper 1 (Biology)
Overview
What a reflex action is and why it protects the body, the parts of a reflex arc in order, why a reflex is faster than a voluntary action, the relay neurone in the spinal cord, how synapses slow an impulse, the hot pan and blinking reflexes, why a person is aware of a reflex, and why the same stimulus always gives the same response.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Name the parts of a reflex arc in the order an impulse passes through them.
Key term
Where is the relay neurone of a spinal reflex arc found, and why does this matter?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a reflex action?
Model answer
A fast, automatic response to a stimulus that happens without conscious thought.
- 2
Name the parts of a reflex arc in the order an impulse passes through them.
Model answer
Stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response.
- 3
Why are reflex actions important to the body?
Model answer
They protect it from harm by producing a response before there is time to think about the stimulus.
- 4
Explain why a reflex arc produces a faster response than a voluntary action.
Model answer
The impulse passes through only three neurones and two synapses and does not travel to the conscious part of the brain for a decision to be made.
- 5
Where is the relay neurone of a spinal reflex arc found, and why does this matter?
Model answer
It is in the spinal cord, so the impulse can pass straight from the sensory neurone to the motor neurone without going up to the brain, which keeps the pathway short.
- 6
Why does each synapse slow an impulse down slightly?
Model answer
The neurotransmitter has to be released and diffuse across the gap before a new impulse can start in the next neurone.
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