Cardiovascular System Heart

Heart Location – Mediastinum Pericardial Sac Pericardial Cavity Pericardial Fluid Parietal Pericardium

Heart Wall Epicardium = Visceral Pericardium Myocardium Endocardium Trabeculae carneae Endocardium

Heart Chambers Atria (Atrium) Auricles Interatrial septum

Heart Chambers Ventricles Interventricular septum Coronary sulcus

Valves Atrioventricular (Tricuspid & Bicuspid) Semilunar Chordae tendineae Papillary muscles Semilunar Pulmonary Aortic

Vessels Superior Vena Cava Inferior Vena Cava Pulmonary Trunk (Arteries) Pulmonary Veins Aorta

Coronary Circulation Aorta Coronary arteries Myocardium Cardiac veins Coronary sinus Right atrium

Cardiac Muscle physiology Myocardium Automated excitement No graded responses No tetany No anaerobic metabolism

Cardiac Muscle Striated, Involuntary Intercalated discs Refractory period prevents tetany Energy ATP – aerobic metabolism Coronary circulation providing O2

Excitation of cardiac muscle Depolarization to threshold is spontaneous due to decreased outflow of K+ Sinoatrial node (SA) Depolarizes every .8 sec. At rest Depolarizes due to change in permeability Pacemaker

Conduction Spread to both atria AV node (.1 sec. Delay) AV Bundle (Bundle of His) Purkinje = Conduction fibers Myocardial cells of ventricle

Cardiac Cycle Systole RV = 30 mm Hg LV = 120 mm Hg

Cardiac Cycle Diastole

Time for cardiac cycle Entire cycle is .8 sec. Atrial systole .1 sec Atrial diastole .7 sec Ventricular systole .3 sec Ventricular diastole .5 sec

Pressure Curves Atrium Ventricle Aortic

Heart Sounds S1 = AV valves closing S2 = Semilunar valves closing

CARDIAC OUTPUT CO = HR x SV 5-6 liters/minute 70 beats/minute x 80 mls/beat

Cardiac Reserve Difference between maximum CO and resting CO Can increase 700%!!

Heart Rate Control Sympathetic Stimulation Parasympathetic Stimulation

Stroke Volume Control SV = End-diastolic volume – End-systolic volume Length of diastole Venous Return

Stroke Volume Control End-systolic volume Frank-Starling Law Sympathetic Nervous System Parasympathetic Nervous System

Factors influencing Cardiac Function Cardiac Center in Brainstem Exercise,Temperature Ions (K, Ca, Na) Sex Age

Electrocardiogram EKG, ECG Leads P wave – atrial depolarization QRS complex – ventricular depolarization T wave - ventricular repolarization