Cardiovascular System Question And Answers

Cardiovascular System Question And Answers

What is Cardiac cycle? Describe events occurring during normal cardiac cycle.
Answer:

Cardiac Cycle Definition:

• The sequence of changes in the pressure flow in the heart chambers and blood vessels in between the two subsequent cardiac contractions is known as cardiac cycle

Cardiac Cycle Events:

• In the beginning of each cardiac cycle.
  1. Both atria and ventricles are relaxed.
  2. A-V valves are open.

1. Artial systole:

Artial systole Definition:

• The contraction of atria is called atrial systole.

Artial systole Duration:

• It lasts for 0.1 sec.

Artial systole Features:

• Intra atrial and intraventricular pressure increases.
• It propel approx 30% additional blood into the ventricles.
• Throughout the atrial systole due to pressure gradient the blood flows from the atria into the ventricles.

 

2. Ventricular systole:

Ventricular systole Defintion:

• The contraction of ventricle is called ventricular systole.

Ventricular systole Duration:

• Total duration – 0.3 sec.
  1. Isovolumetric ventricular contraction – 0.05 sec.
  2. Ventricular systole proper – 0.25 sec.

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Ventricular systole Features:

1. Isovolumetric ventricular contraction.
   • Semilunar valves are already closed.
   • Ventricular pressure exceedes atrial pressure.
   • This causes closure of AV valves.
   • The ventricles are now as closed chambers.
   • There is rapid increase in the pressure of ventricles.
   • However, there is no change in the volume of ventricular chambers.
   • Thus, it is called is volumetric ventricular contraction.
   • It causes bulging of A-V valve
2. Ventricular systole proper.
   • Ventricular pressure exceeds the pressure in aorta and pulmonary artery.
   • Semilunar valves are open.
   • It leads to ejection of blood from the ventricles.
   • Ejection of blood occurs in two stages.
     1. Rapid ejection period – 0.1 sec.
        • Intraventricular pressure rises to maximum. due to opening of semilunar valves, a large amount of blood is rapidly ejected from ventricles.
     2. Slow ejection period – 0.015 sec.
        • Ventricular pressure declines
        • This leads to slow ejection of blood with much less force.

3. Ventricular diastole:

Ventricular diastole Definition:

• The relaxation of ventricles is called ventricular diastole.

Ventricular diastole Duration:

• Total duration -0.5 sec.
  1. Protodiastoe – 0.04 sec.
  2. Isometric ventricular relaxation -0.08 sec.
  3. Ventricular diastole proper – 0.28 sec.
  4. Filling phase – 0.1 sec.

Ventricular diastole Features:

1. Protodiastole.
   • Ventricular pressure reduces
   • Pressure in aorta and pulmonary artery increases
   • Valves are closed.
   • Atrial pressure exceeds that of ventricle.
2. Isometric ventricular relaxation.
   • Ventricles are relax.
   • As all valves are closed, ventricles are again closed chambers.
   • Thus as there is no change in volume of ventricle, it is called isometric ventricular relaxation.
3. Ventricular diastole proper.
   • About 70% of ventricular filling occurs during this stage.
   • It includes.
     1. Rapid filling phase.
        • As A-V valves are open, sudden rush of blood from atrium into ventricles occurs.
        • Ventricular pressure remains low.
        • Atrial pressure also falls.
     2. Slow filling called diastasis.
        • It is due to continuous filling of both atrium and ventricles.
     3. Atrial diastole.
        • Definition:
          • The relaxation of atria is called atrial diastole
        • Duration:
          • 0.7 sec.
        • Features:
          • Atrial pressure gradually increases.
          • A-V valves are opened.