atrial pressure

atrial pressure increases when :

• a wave : atrial contraction
• c wave: as ventricle contracts - due probably to bulging of AV valve into atria
• v wave: increases slowly at atrium fills with blood from periphery

atrial pressure reduces when :

• x descent: atrium relaxes and tricuspid valve is pulled downwards
• y descent : tricuspid valve opens and blood flows into right ventricle

cardiac cycle

CARDIAC CYCLE

• one cardiac cycle : one complete cycle that encompasses atrial and ventricle contraction and relaxation

• 

• P wave	atrial depolarization & contraction	fills the ventricles	cuspid valves open while valves of vena cava and pulmonary veins are closed
  QRS complex	atrial repolarization and relaxation & simultaneous ventricular depolarization and contraction	empties the ventricles	cuspid valves are closed while semilunar valves are open
  T wave	ventricular repolarization and relaxation	heart relaxes	cuspid and semilunar valves are closed
  pause	myocardium at rest	atria fill after a pause of some length	valves of vena cava and pulmonary veins open so atria can fill

Coronary arteries and the tributaries