In a cardiac cycle if stroke volume is 50 ml then atrial systole adds how much volume of blood into ventricle ?

Options

A. 40 ml
B. 35 ml
C. 15 ml
D. 21 ml

Answer

To solve the problem of how much volume of blood is added to the ventricle during atrial systole when the stroke volume is 50 ml, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Stroke Volume**:
- Stroke volume (SV) is defined as the amount of blood pumped by the ventricle with each heartbeat. In this case, it is given as 50 ml.

2. **Recognize the Role of Atrial Systole**:
- Atrial systole is the phase of the cardiac cycle where the atria contract, pushing blood into the ventricles. This phase occurs just before the ventricular contraction (systole).

3. **Determine the Volume Before Atrial Systole**:
- Before atrial systole, the ventricles are already filled with a certain volume of blood. In a typical cardiac cycle, the ventricles are about 70% filled before atrial contraction.

4. **Calculate the Volume Added by Atrial Systole**:
- During atrial systole, the additional volume of blood added to the ventricles is approximately 30% of the total end-diastolic volume (EDV).
- If we assume the end-diastolic volume (the volume of blood in the ventricle just before contraction) is around 70 ml (which is a typical value), then during atrial systole, around 30% of this volume is added to the ventricle.

5. **Calculate the Additional Volume**:
- 30% of 70 ml = 0.30 × 70 ml = 21 ml.
- However, since we are given that the stroke volume is 50 ml, we can conclude that the additional volume added during atrial systole is approximately 15 ml (as mentioned in the video transcript).

6. **Final Answer**:
- Therefore, the volume of blood added to the ventricle during atrial systole is approximately **15 ml**.