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NCLEX Style Cardiac Cycle and Heart Function Study

NCLEX-style cardiac cycle & heart function study guide. Covers key phases: diastole (ventricular filling) and systole (ventricular contraction), emphasizing blood flow driven by pressure gradients. Ideal for quick nursing exam review.

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    4 NCLEX-Style Cardiac Cycle & Heart Function Study Guide Key Concept: Blood circulates in a continuous loop, moving from areas of high pressure low pressure due to shifting pressure gradients. Cardiac Cycle = One Complete Heartbeat Two Phases: • Diastole: ■ . Ventricles relax & fill with blood (2/3 of cycle) • Systole: Ventricles contract & eject blood into arteries (1/3 of cycle)

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    Diastole (Filling Phase) • 4 AV valves open (tricuspid & mitral) • Atria pressure > ventricular pressure -> ■ passive blood flowinto ventricles Early filling = protodiastolic phase • £ At end of diastole— -Atria contract and push -25% of stroke volume into ventricles Called atrial systole, presystole, or atrial kick • | Important: Atrial systole occurs during ventricular diastole! Systole (Pumping Phase) 1. Ventricles fill —> Pressure rises 2. AV valves (mitral & tricuspid) close Closure - S1 (First Heart Sound) Q Prevents backflow into atria 3. All 4 valves briefly closed — isovolumic contraction 4. Ventricular pressure > aortic/pulmonic pressure —> semilunar valves open 5. Blood rapidly ejected 6. After ejection —> Ventricular pressure drops , Semilunar valves SV valves (aortic & pulmonic) close Closure = S2 (Second Heart Sound) Signals end of systole Diastole Begins Again

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    All 4 valves closed isovolumic relaxation • Atria fill —* pressure rises • AV valves (triscupid/ mitral=biscupid) open — ► new cycle begins Right vs Left Heart Events • Left Heart Right Heart Higher pressure system Lower pressure system Pumps to body (systemic) Pumps to lungs (pulmonary) Events occur slightly earlier Events occur slightly later > S1M1 before T1 > S2: A2 before P2 > Heart Sounds > Normal Heart Sounds (lub, dub) * Sound Description Heard Best 51 Closure of AV valves (mitral/tricuspid) —* start of systole Apex 52 Closure of semilunar valves SV (aortic/pulmonic) end of Base systole

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    "LUB" Mitral & tricuspid valves are shutting "DUB'* Aortic & pulmonic valves are shutting DULL GALLOPING 5OUND Indicates early diastole in rapid ventricular fil ing Heart Sounds Chart - S1 to S4

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    Sound When You Hear It What Makes the Sound Best Place to Hear Extra Info I Mnemonic > S1 ("Lub") Start of systole (heart starts squeezing) AV valves (mitral A tricuspid) close Apex (bottom of heart by ribs) f 'LUB = AV slam shut so blood doesn't go back up > S2("Dub”) End of systole (heart stops squeezing, starts relaxing) _• Semilunar valves (aortic A pulmonic) close Base (top of heart, near 2nd rib) < DUB'' = blood stops from flowing backward > S3 ("Ventricular gallop") Just after S2 <1 Caused by fast blood filling into ventricles Use bell of stethoscope! Low-pitched Often heard in heart failure Think 'Lub-dub-ta'' > S4 ("Atrial gallop") Just before S1 A Caused when atria squeeze into a stiff ventricle Use bell, heard best at apex ♦ Seen in high blood pressure Sounds like Ta-lub-dub ' (D Extra Tips for Memory: • S1 = Start (of squeezing) • S2 = Stop (relax begins) • S3 = Squishy ventricle (heart is too full, think failure) • S4 = Stiff ventricle (heart is too stiff, like in high BP) Sound Patterns: • Normal: Lub-Dub (S1-S2) • With S3: Lub-Dub-Ta (sign of volume overload )

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    With S4: Ta-Lub-Dub (sign of stiff heart u ) 4 What Are Murmurs, and Why Do We Hear Them? A heart murmur is a "whooshing” sound you hear when blood isn't flowing smoothly through the heart — kind a like when a hose gets kinked or when water rushes too fast 1. Blood is Moving Too Fast (f Velocity) • iv' fever • J pregnant • 1, exercising a lot • thyroid problems (like hyperthyroidism) Blood zooms through like liver = murmur 2. Blood is Too Thin (| Viscosity) • Anemia (low red blood cells) — Less thick blood = more swirling sound = murmur

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    |s» 3. Heart Has a Problem with Its Structure • v'o Stenosis - valve is too tight (blood squeezes through like a clogged drain) • Regurgitation - valve is too loose (blood leaks backward flow) • * Septal defect - hole in the wall between heart chambers All of these cause swishing/rumbling - heart mumiur £ ) Easy Way to Remember: FAST BLOOD THIN BLOOD : or a BROKEN DOOR = murmur! % How Heart Sounds Are Described 1. Pitch (Frequency) High or low 2. Intensity (Loudness): Loud or soft

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