 2/3 of the mass lies to the left of the body’s midline  The apex lies on the diaphragm

 Pericardium: 2 layered sac surrounding the heart  Myocardium: muscle tissue making up the walls of the chambers  Endocardium: smooth lining of heart chambers

 Atria: receiving chambers ◦ Thin walled do to minimal work load ◦ Most work is done by gravity  Ventricles: discharging chambers ◦ More muscular

 The Tricuspid Valve ◦ Right Heart ◦ 3 flaps  The Mitral or Bicuspid Valve ◦ Left heart ◦ 2 flaps

 Pulmonary Semilunar Valve: at the beginning of the pulmonary artery  Aortic Semilunar Valve: at the beginning of the aorta

Systole: Contracion Diastole: Relaxation

 Body  Vena Cava  Right Atrium  Tricuspid Valve  Right Ventricle  Pulmonary Semilunar Valve  Pulmonary Artery  Lungs

 Pulmonary Vein  Left Atrium  Mitral Valve  Left Ventricle  Aortic Semilunar Valve  Aorta  Body

 Blood which supplies oxygen and nutrients to the myocardium of the hear, flows through the right and left coronary arteries.

 SA (sinoatrial) Node: the pacemaker  Generator of heart rhythm  Found in the right atrium  Initiates the electrical sequence  Starts contraction of the atria  AV (atrioventricular) Node:  triggers contraction of the ventricles via perjunkie fibers and bundle of His  Ventricles contract from the bottom upwards.  This makes sense because the outlets for the blood flow are at the top.

 An electrocardiogram (ECG or EKG) is a graphical recording of the electrical events occurring within the heart.  A normal ECG has 3 deflections:  P Wave: Atrial Systole (initiated by SA Node)  QRS Complex: Ventricular Systole  T Wave: Ventricular Diastole  Note: Atrial Diastole is masked by ventricular systole

 A long interval reveals that an impulse has been slowed or has taken a longer route.  A short interval reflects an impulse which followed a shorter route.  If a complex is absent, the electrical Impulse did not rise normally, or was blocked at that part of the heart.  Lack of normal depolarization of the atria leads to an absent P wave.  An absent QRS complex after a normal P wave indicates the electrical impulse was blocked before it reached the ventricles.  Abnormally shaped complexes result from abnormal spread of the impulse through the muscle tissue, such as in myocardial infarction where the impulse cannot follow its normal pathway because of tissue death or injury. Note: Electrical patterns may also be changed by metabolic abnormalities and by various medicines.