What is the typical transmembrane potential for a myocardial cell at rest?

The typical transmembrane potential for a myocardial cell at rest is approximately -90 mV. This value represents the resting membrane potential of cardiac myocytes, which is crucial for maintaining the cells' excitability and overall function.

At rest, myocardial cells are polarized, meaning there is a negative charge inside the cell relative to the outside. This polarization is primarily due to the distribution of ions across the cell membrane, particularly sodium and potassium. The resting potential is largely determined by the permeability of the membrane to potassium ions, which are more concentrated inside the cell than outside. As potassium ions diffuse out of the cell, they contribute to the negative charge inside.

Understanding this resting potential is essential because it sets the stage for the electrical activity in the heart, including depolarization and the action potentials that trigger heart contractions. Any significant deviation from this resting potential can affect the cardiac rhythm and overall heart function.

The specified value of -90 mV helps to delineate the excitable state of the cardiac cells, ensuring that they are ready to respond to stimuli while also forming the basis for coordinated contractions of the heart muscle.