Cardiac Cycle Flashcards
How many phases are in the Cardiac Cycle?
5 stages
Name the stages
Late Diastole Atrial Systole Isovolumic Ventricular Contraction Ventricular Ejection Isovolumic Ventricular Relaxation
Describe Late Diastole
Both chambers relaxed, AV valves are open and ventricles fill passively
Describe Atrial Systole
Atrial contraction forces last bit of additional blood into the ventricles (controlled by SAN)
Describe Isovolumic Ventricular Contraction
Pressure in Ventricle is higher than in Atria so the AV valves are pushed shut. Ventricle contracts but does not change volume because the SL valves are still shut.
Describe Ventricular Ejection
Pressure in the Ventricle reaches a value higher than in the aorta and pulmonary artery so the SL valves open and blood is pushed out of the ventricle.
Describe Isovolumic Ventricular Relaxation
Ventricle relax and SL valves shut as the pressure drops.
How does the time spent in Diastole relate to Systole?
2/3 diastole, 1/3 systole
Name 4 pressures associated with the cardiac cycle
Systolic pressure= peak= 120mm/hg
Diastolic pressure= lowest aortic pressure= 80mm/hg
Pulse pressure= Systolic- diastolic pressure = 40mm/hg
Mean Arterial Pressure= diastolic+ 1/3pulse pressure= 75mm/hg
What is important to remember about these pressures?
They apply to the LEFT side of the heart
What is different in THE RIGHT side?
The values are around 1/5 of the left
Less pressure is required because the blood is only going to the lungs.
The stroke volume is the same. SERIES circuit
Name 4 Volumes associated with the Cardiac Cycle
END Systolic Volume= 60ml
END Diastolic Volume= 140ml
Stroke Volume= EDV- ESV= 80ml
Ejection Fracture= SV/EDV (should be 2/3)
Name the three phases of Filling
Rapid, slower and active (action of atria)
Describe the process of Ejection
Rapid phase then a slower phase
Why is it important to have a rapid phase at the start?
Limits the effect that rising HR has on stroke volume.
