Diastole Definition
The heart relaxes during diastole, allowing blood to replenish each atrium and ventricle. Diastole is the lengthier of the two phases, with the contraction of the heart muscles occurring rather swiftly. To enable blood to return to the heart, the diastole phase must be extended. Because the atria and ventricles cease contracting at somewhat different times, diastole may be separated into two types: atrial diastole and ventricular diastole.
The reduction in blood pressure within the ventricle produces a change in the valves inside each ventricle during ventricular diastole. The figure above illustrates this. The semilunar valves seal, blocking the ventricles’ exit pathways from the heart. The reduction in pressure also opens the atrioventricular valves, allowing blood to flow freely between the atriums and ventricles. The bulk of the blood that will be forced into the ventricle enters without force during diastole. The atria contract at the conclusion of diastole, causing an atrial kick, which pumps extra blood into the ventricles. During systole, the following phase of the cardiac cycle, this blood is squeezed out of the heart.
Related Biology Terms
- Systole is the period of the cardiac cycle in which the heart contracts.
- Atrial kick:The tiny quantity of blood added by the atria contracting at the conclusion of diastole phase is known as the atrial kick.
- Atrioventricular valves are the valves that connect the heart’s atria and ventricles.
- Semilunar Valves – Heart valves that connect the ventricles to the arteries that leave the heart.
Question
- Blood from the right atrium spills through the tricuspid valve into the right ventricle. The same happens from the left atrium to the left ventricle. The muscles are relaxed. What is this phase of the cardiac cycle call
- Systole
- Diastole
- This never happens
Answer
B is correct. The diastole phase of the cardiac cycle is necessary to reset the heart and prepare for another pump. The two phases of the cardiac cycle ensure that blood flow is directed in one direction, and helps coordinate the efforts of the atrial and ventricle muscles, so they don’t waste energy moving blood.
Question
- An electrician is working on an electrical outlet. His heart is beating normally, cycling from systole to diastole phases. The electrician grabs a live wire and electricity surges through his body. What phase is his heart in?
- Systole
- Diastole
- This muscle contraction is neither
Answer
A is correct. Even if his heart was in a diastolic state before connecting with the wire, the electrical current flowing through a muscle causes it to contract. Contracting heart muscles put the heart in a systolic state. Although this state was caused by outside electrical stimulation and is therefore prolonged, chemical forces in individual nerve cells create electrical impulses that act in the same way as electrical flow. Doctors can restart a stopped heart using the same mechanism.
