Brain and Mind
- In motor neurons the cytoplasm forms a long fibre surrounded by a cell membrane called an axon.
- Some axons are surrounded by a fatty sheath, which insulates the neuron from neighbouring cells and increases the speed of transmission of a nerve impulse
- In some circumstances the brain can modify a reflex response via a neuron to the motor neuron of the reflex arc, to include keeping hold of a hot dinner plate.
- The variety of potential pathways in the brain makes it possible for the animal to adapt to new situations.
- There is evidence to suggest that children may only acquire some skills at a particular age, to include language development in feral children.
- Some drugs and toxins affect the transmission of impulses across synapses. Ecstasy blocks the sites in the brain's synapses where the chemical serotonin is removed.
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- During a neutralisation reaction, the hydrogen ions from the acid react with hydroxide ions from the alkali to make water: H+(aq) + OH−(aq) → H2O(l).
- Reaction rates vary with the particle size of insoluble chemicals, the concentration of solutions of soluble chemicals and the temperature of the reaction mixture.
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The wave model of radiation
- Wave speed is affected by what waves are travelling along or through (the medium) and that the speed will change if a wave moves from one medium into another.
- A change in the speed of a wave causes a change in wavelength since the frequency of the waves cannot change, and how this may cause a change in direction.
- Where two waves meet, their effects add and that this is called interference.
- If a wave is to carry information, the waves must be made to vary in amplitude or frequency, and that the information is carried by the pattern of the variation. Recall that this process is called modulation.
- The job of the receiver is to reproduce the original sound from the pattern of the variation.
- An important difference between electromagnetic waves and sound waves: electromagnetic waves can travel through empty space, but sound waves can only travel through a substance (solid, liquid or gas)
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