THE HEART 7.5-7.7

The Heart Surrounded by fluid-filled membrane called the pericardium to prevent friction Two pumps divided by a septum that are synchronized Right side = receive deoxygenated blood, pumps to lungs Left side = receives oxygenated blood from lungs and pumps to body

Chambers of the heart Four chambers, composed of 2 thin atria (sin. atrium) two thick ventricles Ventricles are more muscular to pump blood to distant tissues left ventricle has thickest walls, it must force blood throughout body

How blood moves through the heart Deoxygenated blood moves through veins into the superior & inferior vena cava  right atrium  both atria contract  right ventricle  both ventricles contract  pulmonary arteries  to lungs (oxygenated)  pulmonary veins  left atrium left ventricle  aorta  to body

Heart Valves valves prevent blood from flowing wrong way in the heart Atrioventricular valves  separate atria from ventricles Semilunar valves  separate ventricles from arteries (half-moon shaped)

Special Arteries Aorta  largest artery Pulmonary arteries carry blood away from the heart (only one that carries deoxygenated blood) Coronary arteries  supply heart muscle with oxygen/nutrients (moves away from the heart, back to the heart) Blocked coronary artery causes angina (heart pains) due to lack of oxygen

Coronary Bypass Surgery During operation, heart-lung machine takes over Vein in leg is removed Vein is attached from aorta past blockage Another option: bypass with mammary artery Bypass increases blood flow to the area served by the coronary artery

Heart Circulation http://www.intelihealth.com/IH/ihtIH/WSIHW000/8059/8049/317250.html?d=dmtContent

Heart Beats heart undergo over 3 billion contraction cycles in a lifetime heart made of myogenic muscle, can contract without stimulation Rhythmic contractions due to two different bundles of nerves SA node (sinoatrial node), also called pacemaker, starts & keeps heartbeat regular AV node (atrioventricular node) causes ventricles to contract AV node passes impulses to 2 large nerve fibres called Purkinje fibres, that branch & carry impulses throughout ventricles

Contraction Of The Heart & Action Of The Nerve Nodes

Electrocardiogram (ECG) measures changes in electrical potential across heart, & can detect contraction pulses P wave represents contraction of atria QRS wave is ventricular contraction T wave signals the ventricles have recovered ECGs are useful in diagnosing heart abnormalities. Pg. 260

Cardiac Cycle Consists of two parts: Systole = contraction of the heart muscle, blood is forced out Diastole = relaxation of the heart muscle, chambers fill with blood Atria contract while ventricles relax. Valves in heart open & close during cardiac cycle.

Heart Sounds Sound of the heart is valves opening & closing produces a characteristic "lub-dub" sound Atria fill, muscular walls contract, increasing pressure, forcing AV valves to open filling ventricles Ventricles fill with fluid, they contract Lub is the closure of the AV valves Dub is the closing of the SL valves.

The Cardiac Cycle

Hypertension Hypertension, high blood pressure (the silent killer), occurs when blood pressure is consistently above 140/90. Causes in most cases are unknown, although stress, obesity, high salt intake, and smoking can add to a genetic predisposition