Final answer:
During ventricular systole, ventricular cardiac myocytes are depolarized, isovolumetric contraction and systolic blood pressure occurs, and the AV valves are closed. Atrial depolarization represented by the P wave on the ECG occurs before ventricular systole, not during it.
Step-by-step explanation:
During ventricular systole, several processes are taking place in the heart. First, the ventricular cardiac myocytes are depolarized, which is represented by the QRS complex on an ECG reading. This depolarization leads to ventricular contraction, with the resulting pressure increase leading to the closure of the atrioventricular (AV) valves to prevent backflow into the atria. The atria are in a state of relaxation, or diastole, during ventricular systole. Another key event during this phase is isovolumetric contraction, which occurs when the ventricles are completely closed off, with no blood entering or exiting, until the pressure is sufficient to open the semilunar valves, leading to the ejection of blood into the aorta and pulmonary arteries. This increase in pressure is also what is measured as systolic blood pressure.
The atrial cardiac myocytes are not depolarized; this happens earlier and is reflected by the P wave on the ECG, indicating atrial systole. Isovolumetric relaxation, the P wave, atrial depolarization, and action potential in the AV nodal cells occur outside the phase of ventricular systole.