Answer:
Option D, diastole
Explanation:
In one of its more rudimentary explanations, the heart's process by which it pumps blood can be broken into two phases contraction (systole) and relaxation (diastole).
During contraction, or systole, the lower chambers of the heart known as the ventricles squeeze the muscles within the heart walls (myocardium) which shoot blood out of the heart and into circulation. The right ventricle sends deoxygenated blood to the lungs to become oxygenated; the left ventricle sends oxygenated blood to the rest of the body, such as the brain, the heart itself, the vital organs, and the extremities (arms, legs, hands, feet, fingers, and toes).
During relaxation, or diastole, the lower chambers of the heart stop their squeeze, allowing for these chambers to fill with blood given to them via the upper chambers of the heart known as the atria. Doing this allows for the heart to prepare for the next contraction phase.
This contraction-relaxation process continues involuntarily (without thinking) until the patient dies.
In short, the phase in which the patient's heart muscle fibers are relaxed and the heart is filling with blood is called diastole, option D.
Option d, the phase in which the heart muscle is relaxed and filling with blood is known as diastole, and it's critical for the proper functioning of the heart by allowing for adequate blood filling.
When a patient's heart muscle fibers are relaxed and the heart is filling with blood, this phase is called diastole. During the diastolic phase of the cardiac cycle, the heart chambers, which include both the atria and the ventricles, fill with blood as they prepare for the next beat. This is distinct from systole, which is when the heart contracts to push blood out and pump it around the body. Diastole represents a period of relaxation and plays a crucial role in cardiac function by allowing for the filling of the heart with blood, ensuring that sufficient blood volume is pumped with each heartbeat.