Final answer:
- Pericardial membranes reduce friction during heartbeats, ensuring efficient function.
- Ventricular relaxation during atrial contraction allows the heart to fill with blood, maintaining the effective circulation.
Step-by-step explanation:
The pericardial membranes are essential for the function of the heart as they provide a lubricated casing that reduces friction during heart contractions. The pericardial cavity, filled with serous fluid, ensures that as the heart beats, it does not rub against other structures within the chest cavity, which could cause damage and reduce efficiency.
During atrial contraction, or atrial systole, the ventricles relax (ventricular diastole) to fill with blood. This relaxation while the atria contract is important for maintaining the one-way flow of blood and ensuring the chambers are prepared for the subsequent ventricular contraction that will propel the blood out of the heart. If ventricles did not relax properly, it would be difficult to achieve efficient circulation and blood flow.