Complex sentence: The cardiac action potential differs to action potentials found in other types of electrically excitable cells, such as nerves, as well as varying within the heart also, this is due to the presence of different ion channels in different cells (see below).
Split into simpler sentences: The cardiac action potential differs from action potentials found in other types of electrically excitable cells, such as nerves. Action potentials also vary within the heart; this is due to the presence of different ion channels in different cells (see below).