Simple experiments to understand the ionic origins and characteristics of the ventricular cardiac action potential.

Electrophysiological experiments are helpful for students to understand the role of electrical activity in heart function. Papillary muscle, which belongs to the ventricle, offers the advantage of being easily studied using glass microelectrodes. In addition, there is commercially available software that simulates ventricular electrical activity and can help overcome some difficulties, such as voltage clamp experiments, which need expensive apparatus when used for studies on living preparations. Here, we present a class practical session that is taken by undergraduate students at our University. In the first part of this class, students record action potentials from papillary muscles with the use of glass microelectrodes, and they change extracellular conditions to study the ionic basis of the action potential. In the second part of the class, students simulate action potentials using the Oxsoft Heart model (v. 4.0) and model their previous experiments on papillary muscle to quantify the effects. In particular, the model is very helpful in promoting understanding of the effect that extracellular potassium has on cardiac action potential by simulating voltage clamp experiments. This twin approach of papillary muscle experiments and computer modeling leads to a good understanding of the functioning of the action potential and can help introduce discussion of some abnormal cardiac functioning.