Describe the ionic events associated with a ventricular cardiac action potential (80% of marks).
Outline how the action potential relates with the mechanical events of the cardiac cycle (20 %
To achieve a good pass in this question, candidates needed to outline the ionic events
associated with Phase 0 to phase 4 of the ventricular action potential followed by a description of
excitation – contraction coupling. The second part of the question was best answered using a
ventricular pressure-volume loop and overlaying the phases of the ventricular action potential.
Description of the ionic events associated with the action potential phases was generally well
done, but this was as far as many answers went in answering this question. Few candidates
included a description of excitation-contraction coupling in there answer and few candidates
considered an answer to the second part of the question. The use of illustrations helped answer
References: Guyton and Hall Textbook of Medical Physiology, Chp 9