Explain the relationship between the heart's electrical signals and its physical pumping action.

Let's explain the relationship between the heart's electrical signals and its physical pumping action. The heart's electrical activity (the action potential) directly triggers its mechanical response (contraction and relaxation). Here's how they align: The heart muscle begins to contract (the mechanical response) right after the initial electrical surge, known as the depolarization phase* (phase 0) of the action potential. This contraction phase, called systole, reaches its peak at the end of the plateau phase* (phase 2) of the action potential. The heart then starts to relax (the first half of diastole) during the rapid repolarization phase* (phase 3). Finally, the heart is fully relaxed and refilling with blood (the second half of diastole) during the resting potential phase* (phase 4). Essentially, the electrical signal initiates and guides the entire cycle of heart contraction and relaxation. 5 done. You're making progress.