Model Answer for Question 2 Paper 2: AS Psychology, June 2016 (AQA)

Section A - Approaches in Psychology

02 Briefly outline how excitation and inhibition are involved in synaptic transmission. [4 marks]

Suggested Answer: Excitation occurs when receptor stimulation results in an increase in the positive charge of the postsynaptic neuron which increases the likelihood of the neuron firing. Inhibition occurs when receptor stimulation results in an increase in the negative charge of the postsynaptic neuron and decreases the likelihood of the neuron firing.

Summation is the addition of positive and negative post-synaptic potentials. A nerve cell can receive both positive and negative potentials simultaneously. These potentials are summed and if the net effect on the postsynaptic neuron is inhibitory, the neuron will be less likely to fire, and if the net effect is excitatory, the neuron will be more likely to fire. 

Exam Hint: Students often struggle to demonstrate an accurate understanding of excitation and inhibition. Students need to be aware that excitation/inhibition occur at the postsynaptic membrane. Also, students need to avoid common misconceptions (e.g. that excitation refers to ‘more firing’) as this is not accurate. Finally, to access top marks students need to understand the process of summation (see above).