Regarding human cardiac cycle, which of the following statements is false :

Options

A. The time taken for one cardiac cycle is reduced in tachycardia
B. The time interval for joint diastole in heart is about 0.4 seconds
C. The time interval for joint systole in heart is about 0.4 second
D. Left ventricle takes 0.5 seconds to complete one diastole

Answer

To determine which statement regarding the human cardiac cycle is false, we need to analyze each statement provided:

1. **Statement 1**: "Diffusion capacity of CO2 is 20 to 25 times higher than the O2."
- This statement is true. Carbon dioxide (CO2) diffuses more readily across membranes than oxygen (O2), making its diffusion capacity significantly higher.

2. **Statement 2**: "The partial pressure of CO2 is 5 to 6 mmHg less in systemic artery than the pulmonary vein."
- This statement is also true. The systemic arteries carry oxygenated blood, which has a lower partial pressure of CO2 compared to the pulmonary veins that return blood from the lungs, where CO2 is expelled.

3. **Statement 3**: "The partial pressure of O2 is almost the same in the hepatic portal vein and the pulmonary artery."
- This statement is false. The pulmonary artery carries deoxygenated blood from the heart to the lungs, where it gets oxygenated, resulting in a higher partial pressure of O2 compared to the hepatic portal vein, which carries blood from the digestive organs to the liver and has a lower partial pressure of O2.

4. **Statement 4**: "Blood is the medium for the transport of atoms of O2 and CO2."
- This statement is true. Blood serves as the transport medium for gases, including oxygen and carbon dioxide, through hemoglobin and plasma.

Based on the analysis, the false statement is:

**Answer**: The partial pressure of O2 is almost the same in the hepatic portal vein and the pulmonary artery.