ventricular ejection isovolumetric contraction ventricular filling isovolumetric relaxation End diastolic volume and the first heart sound are observed during the \( \square \) phase of the cardiac cycle. The P wave and subsequent atrial contraction are evident during the \( \square \) phase of the cardiac cycle. The semilunar valves open during the \( \square \) phase of the cardiac cycle, allowing blood to exit the ventricles. The dierotic notch occurs during the \( \square \) phase of the cardiac cycle. Submit

Certainly! Let's fill in each blank with the appropriate phase of the cardiac cycle based on the descriptions provided. 1. **End diastolic volume and the first heart sound are observed during the** **_** **isovolumetric contraction** **phase of the cardiac cycle.** - **Explanation:** The end diastolic volume represents the blood volume in the ventricles at the end of ventricular filling. The first heart sound (S1) occurs when the atrioventricular (mitral and tricuspid) valves close, marking the beginning of the **isovolumetric contraction** phase. 2. **The P wave and subsequent atrial contraction are evident during the** **_** **ventricular filling** **phase of the cardiac cycle.** - **Explanation:** The P wave on an electrocardiogram (ECG) corresponds to atrial depolarization, leading to atrial contraction. This contraction occurs during the **ventricular filling** phase, where the atria pump blood into the ventricles. 3. **The semilunar valves open during the** **_** **ventricular ejection** **phase of the cardiac cycle, allowing blood to exit the ventricles.** - **Explanation:** During the **ventricular ejection** phase, the pressure in the ventricles exceeds that in the aorta and pulmonary artery, causing the semilunar valves (aortic and pulmonary) to open and allow blood to be ejected from the heart. 4. **The dicrotic notch occurs during the** **_** **isovolumetric relaxation** **phase of the cardiac cycle.** - **Explanation:** The **dicrotic notch** is a small, brief increase in arterial pressure following the closure of the semilunar valves. This occurs during the **isovolumetric relaxation** phase when the ventricles relax with no volume change, and the semilunar valves have just closed. **Summary of Filled Blanks:** 1. **Isovolumetric contraction** 2. **Ventricular filling** 3. **Ventricular ejection** 4. **Isovolumetric relaxation**