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)
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)
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
• 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
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
• 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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