Cardiac Cycle basics

• Cardiac Cycle:

  • Describes the sequence of events within the heart, which starts with deoxygenated venous blood entering the right atrium & oxygenated blood being ejected into the aorta from where blood starts its journey into the systemic and coronary circulation
• • Cardiac cycle can be divided systole and diastole
  • systole is ventricular contraction
  • diastole is ventricular relaxation
• Basic Principles:

  • blood flows from higher to lower pressure
  • contraction increases the pressure within a chamber
  • relaxation decreases the pressure within a chamber
  • atrioventricular valves open when atrial pressure is higher than ventricular pressure
  • atrioventricular valves close when ventricular pressure is higher than atrial pressure
  • semilunar valves open when ventricular pressure is higher than aortic/pulmonary pressure
  • semilunar valves close when aortic/pulmonary pressure is higher than ventricular pressure