Question

Compare and Contrast the Neuronal Action Potential vs Cardiac Action Potential. Focus on the STEPS (depolorization, refractory period repolorization, Na/K pumps, resting membrane potential, ect...) of the both action potentials and identify the difference(s).
What is the significance and involvement of Calcium ions in the cardiac action potentials? Why are Calcium ions not necessary in the neuronal action potentials, but are essential in the myocardial AP?

Answer 1

The major difference between neuronal action potential and cardiac action potential is duration of action potentials.In a typical nerve the action potential is about 1ms.In skeletal muscle,the action potential duration is approximately 2-5ms.In cardic the action potential range from 200 to 400ms.

Another difference between Cardiac and nerve and muscle action potential is the role of calcium ions in depolarization.The depolarization phase of action potential is causes by opening of sodium channels in nerve and muscle cells.

Ions channels have two fundamental properties.Ion permeation and gating.Four ion permeation decsribes the movement through the open channel.The selective permeability of ion channels to specific ions is a basis of classification of ion channels examples Na+,K+,Ca+2 channels.Size , valency and hydration energy are important determinants of selectivity.Biologically important alkali cations have have high selectivity ratio.

Example 10:1 is the selectivity ratio of sodium channels Na+:K+.