Pressure changes in the heart

• When do the atrioventricular valves open?

  When atrial pressures are greater than ventricular pressures
• When do the semi-lunar valves open?

  When ventricular pressures are higher than aortic / pulmonary pressures
• What are the pressure changes in the heart?

  1. Atria contract (systole), so atrial pressure is greater than ventricular pressure -> AV valves open -> blood flows into relaxed ventricles (diastole)
  2. Ventricles are full and contract -> pressure increases rapidly and exceeds atrial pressure -> AV valves shut
  3. Ventricular pressure exceeds artery pressure -> semi-lunar valves open -> blood is pushed up into arteries
  4. Ventricles relax -> pressure falls below artery pressure -> semi-lunar valves close
  5. Ventricular pressure falls below atrial pressure -> heart is in diastole
• Why do the ventricles have a higher pressure change?

  They have more muscle for stronger contractions to force blood out of the heart and around the body