damage of heart muscle Myocardial ischemia inadequate delivery of oxygenated

Damage of heart muscle myocardial ischemia inadequate

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(damage of heart muscle): Myocardial ischemia : inadequate delivery of oxygenated blood to the heart causes necrosis of heart muscle cells Myocardial infarction (heart attack): abnormal QRS complex waves Heart block : from defects in the cardiac conducting system Atria still beat regularly, but ventricles occasionally fail to be stimulated to contract Complete heart block : impulses from atria not conducted to ventricles at all Atria & ventricles not synchronized with each other
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Mechanical Events of the Cardiac Cycle Mechanical contraction events brought about by rhythmic changes in cardiac electrical activity Cardiac Cycle = alternating periods of contraction (to empty) and relaxation (to fill) of heart chambers (At rest, 1 complete cycle ~ 800 ms) Systole : cardiac muscle contraction & emptying Spread of excitation (depolarization) across heart Diastole: cardiac muscle relaxation & filling Repolarization of cardiac muscle
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Major Events of Cardiac Cycle (centered around venticle activity)Ventricular diastole -ventricles fill with bloodIsovolumetric ventricular contraction-ventricles contract, all 4 valves are closed, pressure risesVentricular ejection-pressure forces blood past the semilunar valves (blood flow to body & lungs)Ventricular repolarization-pressure falls, return to ventricular diastole
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(Note: all 4 valves are never open at the same time) Cardiac Cycle Events From body From lungs To body To lung To lung
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Heart Volume Terminology End-diastolic volume (EDV): volume of blood in the ventricle when filling is complete (volume available for ejection)End-systolic volume (ESV): volume of blood remaining in the ventricle when ejection is complete(amount left depends on contractile force)Stroke volume (SV): volume of blood pumped out by each ventricle per contraction/beat SV=EDV-ESV
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Pressure-volume changes for a single cycle: lef ventricle example 1. AV valve opens 2. Passive ventricular filling . Volume increases considerably and pressure increases slightly as blood enters. 3. Atrial contraction- completes ventricular filling . End-diastolic volume is reached at the end of this phase. 4. AV valve closes 5. Isovolumetric ventricular contraction . Volume remains constant-valves closed; pressure increases markedly. 6. aortic valve opens 7. A stroke volume of blood is ejected . Volume decreases considerably as pressure peaks, then falls slightly as blood leaves. End-systolic volume is reached at the end of this phase. 8. aortic valve closes 9. Isovolumetric ventricular relaxation. Volume remains constant; pressure falls sharply. Repeat – back to step 1 (loop) (EDV) (ESV) (SV)
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Mechanical events also produce Heart Sounds Valve closing produces two normal heart sounds: Caused by vibrations in the walls of ventricles & arteries during valve closure, not by valves snapping shut valve opening does not make sounds First heart sound (S 1 ) or “lub”: closing of the AV valves – signals onset of ventricular systole (contraction) Second heart sound (S 2 ) or “dub/dup”: closing of the semilunar valves (aortic and pulmonary valves) – signals onset of ventricular diastole (relaxation) Lub-dub lub-dub lub-dub…
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Heart Sounds: murmurs
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