Through the physiologic range of parasympathetic input this effect of phase 4 is dominant. If parasympathetic drive is maximized, the maximum diastolic potential will also be affected as a result of increased permeability of the membrane to potassium. The I Ca symbol refers to Current carried by Ca. I K is the symbol for the potassium current mediated by a specific type of potassium channel, the delayed rectifier. The permeability to potassium during repolarization is not greater than at rest, therefore not hyperpolarization.
All muscles resist being stretched.
The ventricular cell and purkinje cell action potentials are very similar and have comparable permeability changes that underlie the various phases of the action potential. Consequently the figure could be labeled either way. Is passive stretch in skeletal muscle comparable to stretch as a result of filling volume in the heart and active tension in skeletal muscle comparable to ejection pressure in heart systole. The passive tension curve of the length tension relationship is a measure of the work done on the muscle by an external force. In skeletal muscle by the antagonistic muscle, in heart by the filling pressure and consequent volume of blood in the ventricular chamber.