CAIE A Level Biology 9700 · Control and coordination
A student uses a microelectrode to record action potentials from a sensory neurone in a taste bud after applying solutions of increasing concentration of sodium chloride. The student observes that as the concentration increases, the frequency of action potentials increases until a maximum frequency is reached. Describe why the refractory period of the neurone limits the maximum frequency of impulses that can be conducted.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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