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CARDIOVASCULAR SYSTEM - Heart, blood vessels, blood - Consists of 2 circuits: - Pulmonary Circuit - Systemic Circuit ANATOMY OF THE HEART Pumps 7,000 liters of blood per day It takes about 1 minute for blood to circulate around the body Contracts 2.5 billion times in a lefetime Size of the heart: 14cm long and 9 cm. wide 2 muscular pumps in one: - left heart pumps blood to the body tissues - right heart pumps blood to the lungs The heart circulates the blood through the circulatory system. Blood carries oxygen and nutrients to the cells Tisssues Covering the Heart Pericardium – serous membrane that surrounds the heart - Fibrous Pericardium – outer layer - Parietal Pericardium – inner lining of fibrous pericardium - Visceral Pericardium – inner layer - Pericardial Cavity – space between the parietal and visceral layers. Contains serous fluid Walls of the Heart Epicardium – visceral pericardium Myocardium – middle layer, thick and consists mostly of cardiac muscle tissue Endocardium – inner layer consisting of epithelium and connective tissue Anatomy of the Heart 1. Consists of 4 chambers - 2 atria – superior chambers, thin muscular walls - 2 ventricles – inferior chambers, thicker muscular walls 2. Valves: - Atrioventricular valves: - Tricuspid: separates right atrium and right ventricle - Bicuspid (mitral): separates left atrium and left ventricle - Semilunar valves; - Pulmonary Semilunar: found between right ventricle and pulmonary artery - Aortic Semilunar: found between left ventricle and aorta Valves direct the flow of blood and prevent backflow of blood Heart Murmur: if a valve is damaged or does not close properly, blood leaks backwards causing a “noise” Blood Supply to the Heart Coronary Arteries – supply blood to tissues of the heart - the first 2 branches of the aorta Cardiac Veins – empty into the right atrium (coronary sinus) Path of Blood through the heart: Vena Cava R atrium tricuspid valve R ventricle Pulmonary semilunar valve Pulmonary artery lungs Pulmonary vein L atrium bicuspid valve L ventricle Aortic semilunar valve aorta body vena cava Heart Attack - A block or narrowing of a coronary artery or one of its branches deproves the myocardial cells of oxygen - Angina Pectoris – may occur during activty or stress - A complete blockage kills heart tissue – Myocardial Infarction (MI), a heart attack THE CARDIAC CYCLE The heart beats in a coordinated fashion - Systole – contraction of the atria - Diastole – relaxation - Cardiac Cycle – contraction and relaxation of the heart Sounds of the Heart “lubb – dupp” - Lubb = ventricular systole, AV valves closing - Dupp = ventricular diastole, pulmonary and aortic valves closing The Heart Conduction System - Sinoatrial (SA) node – maintains rhythym - pacemaker - found in the wall of the right atrium where the superior vena cava enters - Atrioventricular (AV) node – found in the wall between the right atrium and right ventricle in the interatrial septum Functional Syncytium – a mass of merging cells that act as a unit. - atrial syncytium - ventricular syncytium SA Node Junctional Fibers Atrtial Synctium AV node AV Bundle (Bundle of His) Bundle Branches Purkinje Fibers Blood Pressure Systolic blood pressure (the upper number) — indicates how much pressure your blood is exerting against your artery walls when the heart beats. Diastolic blood pressure (the lower number) — indicates how much pressure your blood is exerting against your artery walls while the heart is resting between beats. Normal BP – 120/80 Hypertension: >140/90 Hypotension: <90/60 The EKG Electrocardiogram (ECG or EKG from the German word Elektrokardiogram) is a test that records the electrical activity of the heart. - Measures the rate and regularity of heartbeats, as well as information about the heart anatomy. Interpreting an EKG P wave – atrial depolarization (contraction) QRS complex – depolarization of the right and left ventricles T wave – repolarization of the ventricles PR interval – time for the cardiac impulse to travel from SA node through the AV node QT interval – beginning of QRS complex to end of T wave. Prolonged QT interval is a risk for ventricular tachyarrythmias and sudden death ST segment – segment where the ventricles are depolarized THE WIGGER DIAGRAM End-diastolic volume - the amount of blood in each ventricle at the end of ventricular diastole (the start of ventricular systole) 130 ml End-systolic volume - the amount of blood remaining in each ventricle at the end of ventricular systole (the start of ventricular diastole) 50 ml Stroke volume (SV) - the amount of blood pumped out of each ventricle during a single beat, which can be expressed as EDV – ESV = SV 130ml – 50ml = 80 ml Ejection fraction - the percentage of EDV represented by the SV The stroke volume divided by the EDV or 80/130 = 62% A simple model of Stroke Volume Stroke volume of the heart can be compared to the amount of air pumped from an old-fashioned bicycle pump. The amount varies with the amount of handle movement. The extent of the upward movement corresponds to the EDV; extent of the downward movement corresponds to the ESV Cardiac Output – the amount of blood pumped by each ventricle in 1 minute CO = SV x HR If the stroke volume is 80 ml/beat and the heart rate is 75 bpm CO = 80ml/beat x 75 bpm CO = 6000 ml/min (6 L/min) The EDV is affected by: 1. Filling Time – the duration of ventricular diastole 2. Venous return – the rate of blood flow over this period The ESV is affected by: 1. Preload – the degree of stretching experienced during ventricular diastole, which is directly proportional to the EDV The Frank-Starling Principle (Straling’s Law of the Heart): increases in EDV results in a corresponding increase in stroke volume - Relationship between fiber length and force of contraction - increase blood in heart inc. ventricular distention inc. contraction inc. SV inc. CO 2. Contractility – the amount of force produced during a contraction at a given preload 3. Afterload – the amount of tension the contracting ventricle must produce to force open the semilunar valve and eject blood - The greater the afterload, the longer the period of isovolumetric contraction, the shorter the duration of ventricular ejection, and the larger the ESV Or - As afterload increases, the stroke volume decreases - increases in arterial pressure (HYPERTENSION) increases afterload