Lecture 8 The Cardiac Cycle Flashcards
What is the Cardiac Cycle?
Sequence of events that occur when the heart beats
What are the two phases of this cycle?
- Diastole –> ventricles are relaxed
- Systole –> Ventricles contract
What are the three general principles of the cardiac cycle
- The heart is a biological pump
- Contraction-relaxation creates pressure gradients
- Directs the orderly movement of blood through circulation - Blood flows high pressure –> low pressure
- Events on the right and left sides of the heart are the same but pressures are lower on the right
What happens in the Late Diastole Phase?
Both sets of chambers are relaxed and ventricles fill passively
- pressure of blood in veins higher than pressure in atria or ventricles
What happens in the Atrial Systole Phase?
Atrial contraction “atrial kick” forces a small amount of additional blood into ventricles
- final stage of ventricular filling
- end of ventricular diastole
What happens in Isovolumic ventricular contraction?
First phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves
- No blood sent out yet
What happens in ventricular ejection Phase?
Ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected
What happens in Isovolumic Ventricular Relaxation
Ventricles relax, pressure in ventricles falls, blood flows back into cusps of semilunar valves and snaps them closed
Where do the heart sounds occur during contraction?
First
- Vibrations following closure of the AV valves
- “Lub”
Second
- Vibrations created by closing of the semilunar valve
- “Dub”
What is stroke volume?
Volume of blood taken up during concentration
What information can Pressure Volume Loops provide?
- Stroke Volume
- Atrial Filling Pressure
- Aortic Pressure
If there is higher pressure within the heart, how does this affect the heart?
Heart has to work harder to be just as efficient upon higher pressure values
