CAIE A-Level Biology A2 15.1.6 Membrane Potential Changes Questions

Explain membrane potential changes during an action potential using evidence from each question and mark scheme.

Exam points

Explain membrane potential changes during an action potential.

[Maximum number: 3]

In some brain synapses, the neurotransmitter gamma-aminobutyric acid (GABA) is released. This results in an influx of chloride ions into the postsynaptic neurone.

Suggest and explain whether an action potential would be generated in the postsynaptic neurone if GABA is released into a brain synapse.

any three from:

$1 \mathrm{Cl} l^{-}$ influx makes (inside of postsynaptic neurone) more negative / stays negative ;

2 hyperpolarisation / remains polarised ;

3 (not enough $\mathrm{Na}^{+}$ enter so) less likely to reach threshold ;

4 no depolarisation of (postsynaptic) membrane ;

5 (so) no action potential ;

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CAIE A-Level Biology A2 15.1.6 Membrane Potential Changes Questions question 1