In ECG, P-wave represents the depolarization of atria, which leads to the contraction of both atria. T-wave represents the return of ventricles from excited to normal state. The QRS complex represents the depolarisation of the ventricles, which initiates ventricular contraction. The contraction starts shortly after Q and marks the beginning of systole.
Virtually every cell, tissue, organ, and system in the body is impacted by the circulatory system.
Digestive - Absorbs nutrients and water; delivers nutrients (except most lipids) to liver for processing by hepactic portal vein; provides nutrients essential for hematopoiesis and building hemoglobin.
Endocrine - Delivers hormones: atrial natriuretic hormone (peptide) secreted by the heart atrial cells to help regulate blood volumes and pressures; epinephrine, ANH, angiotensin II, ADH, and thyroxine to help regulate blood pressure; estrogen to promote vascular health in women and men.
Integumentary - Carries clotting factors, platelets, and white blood cells for homeostatis, fighting infection, and reparing damage; regulates temperature by controlling blood flow to the surface, where heat can be dissipated; provides some coloration of integument; acts as a blood reservoir.
Muscular - Provides nutrients and oxygen for contraction; removes lactic acid and distributes heat generated by contraction; muscular pumps aid in venous return; exercise contributes to cardiovascular health and helps to prevent atherosclerosis.