Please describe the pressure changes in the right ventricle during diastole, and illustrate this with a diagram.

Here are the descriptions for the requested diagrams:

A. Pressure changes in the RIGHT ventricle during diastole.

A diagram illustrating the pressure changes in the right ventricle during diastole would typically show pressure on the y-axis and time on the x-axis.

• Phase 1: Isovolumetric Relaxation
  • Starts after the pulmonary valve closes.
  • Right ventricular pressure drops sharply as the ventricle relaxes, but its volume remains constant because both the tricuspid and pulmonary valves are closed.
• Phase 2: Rapid Filling
  • Occurs when the right ventricular pressure falls below the right atrial pressure, causing the tricuspid valve to open.
  • Blood flows rapidly from the right atrium into the right ventricle, leading to a rapid increase in right ventricular volume and a slight initial rise then fall in pressure.
• Phase 3: Diastasis (Reduced Filling)
  • The rate of filling slows down as the pressure gradient between the atrium and ventricle decreases.
  • Right ventricular pressure remains relatively low and stable.
• Phase 4: Atrial Systole (Atrial Kick)
  • The right atrium contracts, pushing the final amount of blood into the right ventricle.
  • This causes a small, final increase in right ventricular pressure and volume just before the tricuspid valve closes and systole begins.

The graph would show a sharp decline in pressure during isovolumetric relaxation, followed by a relatively flat or slightly undulating curve during rapid filling and diastasis, and a small upward spike during atrial systole.

B. Effect of increasing central venous pressure (CVP) on end diastolic volume (EDV).

A clearly labeled graph illustrating the effect of increasing central venous pressure (CVP) on end diastolic volume (EDV) would have:

• X-axis: Central Venous Pressure (CVP) (e.g., in mmHg)
• Y-axis: End Diastolic Volume (EDV) (e.g., in mL)

The graph would show a positive relationship, demonstrating the Frank-Starling mechanism:

• As CVP increases, the venous return to the right atrium and subsequently to the right ventricle also increases.
• This increased filling pressure (CVP) leads to a greater stretch of the right ventricular muscle fibers at the end of diastole.
• Consequently, the End Diastolic Volume (EDV) increases.
• The curve would typically show an initial steep rise, indicating that EDV increases significantly with initial increases in CVP.
• As CVP continues to rise, the curve would gradually flatten, suggesting that the ventricle reaches a point where further increases in CVP lead to smaller increments in EDV, as the ventricle approaches its maximum stretch capacity.

The overall shape of the curve would be an upward-sloping line that eventually plateaus.