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Convert it into a answer of events in cardiac cycle
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The image shows Table 36.3: Events in the Cardiac Cycle from Chapter 36 of a physiology textbook. The analysis tool returned the raw image data rather than the full text table. Based on my clear visual reading of the image, here is the complete structured answer:
Events in the Cardiac Cycle
(Based on Table 36.3, Chapter 36 - Cardiac Cycle)
Key concept: Atria relax in diastole and receive blood from veins. RA receives blood from IVC and SVC, whereas LA receives blood from pulmonary veins. Volume and pressure gradually rise in the atria due to increasing volume of blood.
1. Atrial Systole / Last Rapid Filling
| Structure | Events |
|---|---|
| Atrium | Pressure increases due to atrial systole. Remaining 25% of blood is pushed into ventricles. Results in an "a" wave. |
| Ventricle | Small increase in ventricular pressure due to filling. |
| Great Arteries | Equivalent to diastolic pressure in arteries - Pulmonary trunk: 8 mm Hg; Aorta: 80 mm Hg. |
| Valve Status & Heart Sounds | AV valves open, SLV are closed. |
| Correlation with ECG | Atrial systole occurs at the end of P wave. |
2. Isovolumetric Contraction
| Structure | Events |
|---|---|
| Atrium | Small increase in atrial pressure due to bulging of AV valves into atria. Results in "c" wave. |
| Ventricle | Both AV and SL valves are closed. Ventricles contract, resulting in a tremendous increase in pressure. When ventricular pressure equals diastolic pressure, SLV opens. |
| Great Arteries | Equivalent to diastolic pressure in arteries. |
| Valve Status & Heart Sounds | AV valves and SLV closed. |
| Correlation with ECG | R wave coincides with beginning of isovolumetric contraction. |
3. Rapid Ejection
| Structure | Events |
|---|---|
| Atrium | Atrial pressure becomes higher than ventricular pressure and forces open the AV valves. Rapid filling of ventricles takes place due to pressure gradient. |
| Ventricle | On opening of SLV, blood is rapidly and forcefully ejected out into the arteries (75%). Contraction continues and ventricular pressure becomes as high as systolic pressure of arteries. |
| Great Arteries | Pressure increases due to ejection of blood from ventricles. |
| Valve Status & Heart Sounds | AV valves close. SLV open. Produces First Heart Sound (S1). |
| Correlation with ECG | T wave begins in the middle of ventricular systole and ends with the end of isovolumetric relaxation phase. |
4. Slow Ejection
| Structure | Events |
|---|---|
| Atrium | (Same as rapid filling - atrial pressure builds.) |
| Ventricle | Pressure in the ventricles drops and decreases in the force of ejection of blood. Remaining 25% of ejection fraction (EF) is pumped out. |
| Great Arteries | Pressure slowly becomes higher than ventricular pressure. |
| Valve Status & Heart Sounds | AV valves close. SLV open. |
5. Isovolumetric Relaxation
| Structure | Events |
|---|---|
| Atrium | (Continues receiving blood from pulmonary veins.) |
| Ventricle | Closure of SLV. Ventricles begin to relax, dropping pressure tremendously. |
| Great Arteries | Higher pressure in arteries compared to ventricles causes backflow of blood into ventricles. This results in sudden closure of SLV and reflection of blood back into arteries, producing the dicrotic notch. |
| Valve Status & Heart Sounds | AV valves and SLV closed. Produces Second Heart Sound (S2). |
6. Rapid Filling (Early Diastole)
| Structure | Events |
|---|---|
| Atrium | Atrial pressure becomes higher than ventricular pressure and forces open AV valves. Rapid filling of ventricles takes place. |
| Ventricle | Pressure slowly decreases to DBP (diastolic blood pressure). |
| Valve Status & Heart Sounds | SLV closed. AV valves open when ventricular pressure becomes less than atrial pressure. Produces Third Heart Sound (S3). |
7. Diastasis
| Structure | Events |
|---|---|
| Atrium | Pressure in atria and ventricles become almost equal, resulting in minimal or no flow - the "stasis" or "dia-diastolic" term. This is the longest period in ventricular diastole. When HR increases up to 180 bpm, this period shortens without affecting the efficiency of the heart. |
| Great Arteries | Pressure slowly decreases to DBP. |
| Valve Status & Heart Sounds | AV valves open. SLV closed. |
8. Last Rapid Filling (Atrial Systole begins again)
| Structure | Events |
|---|---|
| Atrium | (Same as discussed in column 1 - atrial systole pushes remaining blood into ventricle.) |
| Ventricle | (Same - last 25% of filling occurs.) |
| Valve Status & Heart Sounds | AV valves open. SLV closed. Last rapid filling produces Fourth Heart Sound (S4). |
Summary: Heart Sounds
| Sound | Phase | Cause |
|---|---|---|
| S1 | Start of ventricular systole | Closure of AV valves (Mitral + Tricuspid) |
| S2 | End of ventricular systole | Closure of SL valves (Aortic + Pulmonary) |
| S3 | Early diastole (Rapid filling) | Blood rushing into ventricle; ventricular pressure less than atrial |
| S4 | Late diastole (Atrial systole) | Last rapid filling due to atrial contraction |
Summary: ECG Correlation
| ECG Event | Cardiac Phase |
|---|---|
| End of P wave | Atrial systole |
| R wave | Beginning of isovolumetric contraction |
| T wave onset | Middle of ventricular systole |
| T wave end | End of isovolumetric relaxation |
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