Page 138 - Physiology and Pathophysiology MNU 2024-2025 نظرى

Clinical pharmacy 2024/2025 Level 2 Pharm D Physiology and Pathophysiology (MD303)
Cardiac cycle

Events that occur during a single cardiac cycle (Single Heart Heat) ➔ It takes 0.8 second.
✓ repeating pattern of a) contraction (systole) & b) relaxation {diastole) of the heart chambers

End Diastolic volume [EDV) Stroke Volume (SV) End systolic volume [ESV] Isovolumetric phase
Volume of blood in ventricle at the end of Volume of blood ejected Volume of blood remaining left Ventricular volume is constant when
diastole just before contraction from ventricle during in ventricles at end systole all valves are closed
[EDV=SV+ESV] systole

Phases

1. The ventricular pressure < Atrial pressure.
1) Ventricular
 AV valves are opened, SL valves are closed.
Filling
2. Ventricular filling from the atria begins (80%)

1. The atria contract ( Atrial pressure) & The ventricle relaxed.
2. Ventricular filling (70 -90 % of blood) starts before Atrial systole.
2) Atrial Systole
3. Atrial systole pushes more blood (10-30 %) into the ventricles.
 AV valves are opened & SL valves are closed
1. The ventricles contract  ventricular pressure > Atrial pressure.
 AV valves are closed due to pressure ➔ produce the first heart sound. لولاا توصلا
3) Isovolumetric
2. Ventricular pressure < Aortic pressure (artery pressure) ➔ SL valves are closed.
Ventricular
 No blood leaves the ventricle during this phase.
Contraction
3. Ventricular volume remains constant since all valves are closed. (Volume of blood in the
ventricle = EDV)
1. The ventricles continue to contract & ventricular pressure > aortic pressure.
4) Ventricular
 SL valves are opened.
Ejection
2. Rapid ejection of blood from the left ventricle into the aorta, from right to pulmonary artery

3. ↓ Ventricular volume. 4. Volume of blood ejected = SV.

 AV valves are still closed & atrial filling begins.

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