Pearson Edexcel Level 3 GCE 9BI0/03 2022 Biology B Advanced PAPER 3: General and Practical Principles in Biology

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Answer ALL questions. Write your answers in the spaces provided. 1 Nerve impulses are transmitted along neurones. (a) (i) In the time period between two nerve impulses, the potential difference ac... ross the membrane is –70 mV. State the term given to this potential difference. (1) .................................................................................................................................................................................................................................................................................... (ii) When the neurone is stimulated, an action potential may occur in the axon, due to the change in permeability of the membrane to ions. The graph shows an action potential. 2.52.01.51.00.5 +50 +30 +10 –10 –30 –50 –70 –90 Time / ms Membrane potential / mV Describe what happens in the axon membrane to cause the change in potential difference between 0.55 ms and 0.80 ms. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................. [Show More]

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