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UM BIOH 113 - Heart Physiology
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BIOH 113 1st Edition Lecture 11Outline of Last Lecture I. Membrane PotentialII. Cardiac Muscle ContractionIII. Heart physiologyOutline of Current Lecture I. Heart PhysiologyII. ElectrocardiographyIII. Cardiac Output and ReserveCurrent LectureI. Heart Physiology:a. Sequence of Excitation:i. Sinoatrial (SA) node generates impulses about 100 times/minuteii. Atrioventricular (AV) node delays the impulse approximately .1 secondiii. Impulse passes from the atria to the ventricles via the atrioventricular bundle (bundle of His)iv. AV bundle splits into two pathways in the interventricular septum (bundlebranches)1. Bundle branches carry the impulse toward the apex of the heart2. Purkinje fibers carry the impulse to the heart apex and ventricular wallsb. Extrinsic Innervation of the Hearti. Heart is stimulated by the sympathetic cardioacceleratory centerii. Heart is inhibited by the parasympathetic cardioinhibitory centerII. Electrocardiographya. Electrical activity is recorded by an electrocardiogram (ECG)b. P wave corresponds to depolarization of the atriac. QRS complex corresponds to ventricular depolarizationd. T wave corresponds to ventricular repolarization e. Atrial repolarization record is masked by the larger QRS complexThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. Cardiac Cyclea. Refers to all events associated with blood flow through the hearti. Systole: contraction of the heart muscleii. Diastole: relaxation of the heart muscleb. Heart sounds:i. Associated with closing of heart valves1. First sound (S1) occurs as AV valves close and signifies beginning of systole2. Second sound (S2) occurs when semilunar valves close at the beginning of ventricular diastolec. Phases of the cardiac cycle:i. Ventricular filling—mid to late diastole1. Heart blood pressure is low as blood enters atria and flows into ventricles2. AV valves open then atrial systole occursii. Ventricular systole:1. Atria relax2. Rising ventricular pressure results in closing of valves3. Isovolumetric contraction phase4. Ventricular ejection phase opens semilunar valvesiii. Isovolumetric relaxation—early diastole1. Ventricles relax2. Backflow of blood in aorta and pulmonary trunk closes semilunar valves3. Dicrotic notch: brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valvesIV. Cardiac Output and Reservea. Cardiac output (CO) is the amount of blood pumped by each ventricle in one minuteb. CO is the product of heart rate and stroke volume (SV)c. Heart rate is the number of heart beats/minuted. SV is the amount of blood pumped out by a ventricle with each beate. Cardiac reserve is the difference between resting and maximal COf. Regulation of SV:i. SV= end diastolic volume (EDV) minus end systolic volume (ESV)ii. EDV= amount of blood collected in a ventricle during diastoleiii. ESV= amount of blood remaining in a ventricle after


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UM BIOH 113 - Heart Physiology

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