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7 Cards in this Set
- Front
- Back
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What is the definition of a Cardiac cycle?
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series of events that occurs during one complete heartbeat
electrical systole - spreading of depolarization wave by SA node mechanical systole - contraction of cardiac muscle (P and V change), followed by relaxation Closure and open of cardiac valves generate heart sounds |
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What happens in the Atrial systole phase?
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ventricles are relaxed
contraction of atria --> increased atrial P --> pressure gradient forces blood from atria to ventricles through opened AV valves --> rapid filling of ventricles atrial muscle contraction prevents blood regurgitation 20-30 % (25 ml) of blood added to final ventricular filled volume (EDV, 130 ml) |
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What happens in the ventricular systole phase?
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isovolumic and isometric contraction
increased intraventricular P --> reverse P closes the valves volume remains constant intraventricular P exceeds BP in aorta (80 mm Hg) and pulmonary trunk (20 mm Hg) --> semilunar valves open Ejection: -opening of aortic and pulmonary valves -more P, blood is accelerated and ejected very rapidly from ventricles into arteries (70 % of blood in ventricles) -aortic and pulmonary arterial P increases to systolic peaks -ejection decreases P and ejection rate SV: -volume of blood ejected from each ventricle during ventricular systole ESV: -volume of blood in each ventricle after systole ESV = EDV - SV EF = SV/EDV X 100 (65 %) |
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What happens during Atrial and Ventricular Diastole?
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Protodiastole:
-intraventricular P lower than arteries but kinetic energy keeps blood flowing -backflow closes semilunar valves and ventricular chambers become closed Isovolumic (isometric) relaxation: -ALL valves close, P drop without drop in volume -lower intraventricular P till it is lower than intra-atrial --> opening of AV valves Ventricular Filling: -relaxation of ventricular myocardium --> rapid filling -ventricular P and volume increase --> reduced filling last part of ventricular diastole is atrial systole --> RAPID active filling |
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What are the different heart sounds?
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produced by vibration of closing valves and turbulent blood flow
First and second = S1 and S2 and loud enough to be heard through stethoscope S3 and S4 are not loud First heart sound: -onset of ventricular systole (isovolumic contraction) -low intensity and soft Lub -closure of and vibration of AV valves Second Heart Sound: -beginning of diastole (protodiastole and isovolumic relaxation) -high and sharp dub -shorter than 1st sound -closure and vibration of semilunar valve 3rd and 4th Heart Sounds: 3rd: -end of rapid filling phase -heard about 60 % of the time -vibration of ventricular muscle 4th: -not heard in normal people -blood turbulence during atrial systole |
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What are Heart Murmurs?
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abnormal heart sound from stenosis or incompetence of valve
-increase turbulence of blood through abnormal valve innocent murmurs: -occur in childen, not pathological pathological murmurs: systolic: -mitral or tricuspid valve incompetence -aortic or pulmonary stenosis diastolic: opposite |
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What affects Cardiac Cycle?
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CC = 60 s/HR
increase HR = lowering CC ventricular diastole is more affected than systole 0.12 is minimum interval for refilling of ventricles --> diastolic interval is the chief factor limiting maximal useful HR |
