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19.8 Cardiac Cycle

A&P 19.8 Cardiac Cycle

What is the Cardiac cycle? All events in heart from the start of one heart beat to the start of the next
What does the Cardiac Cycle include? Systole (contraction) and Diastole (relaxation)
When does pressure increase? During contractions, and decreases during relaxation
In what direction does blood move down? its pressure gradient (high to low)
What do valves do? Ensure that blood flow is forward (closure prevents backflow)
What RAISES ventricular pressure? Ventricular contraction
What happens to the valves during ventricular contraction? AV valves pushed closed; Semilunar valves pushed open and blood ejected to artery
What LOWERS ventricular pressure? Ventricular relaxation
What happens to the valves during ventricular relaxation? Semilunar valves are closed (b/c no pressure from below keeping them open) and AV valves are open (b/c no pressure pushing them closed)
What are the events of atrial contraction and ventricular filling? SA node starts atrial excitation/contraction pushing blood into ventricles to be filled to end-diastolic volume (EDV). Atria relax for remainder of cardiac cycle
What happens in Isovolumetric contraction? Purkinje fibers initiate ventricular excitation/contractions so pressure rises and AV valves are pushed closed. Ventricular pressure is still less than atrial trunk pressure, so semilunar valves are still closed.
Why does the ventricles continue to contract during ventricular ejection? So that ventricular pressure rises above arterial pressure
When are the semilunar valves forced open? As blood moves from ventricles to aterial trunks
What is stroke volume (SV)? Amount of blood ejected by ventricule
What is "incorrect" def of End systolic Volume (ESV)? Amount of blood remaining in ventricle after contraction finishes.
What is the equation for ESV? EDV - SV ; Ex: 60 mL = 130 mL - 70 mL
What is the definition of isovolumetric? The time when all valves are closed , blood neither enters nor leaves
What are the AV valves doing during isovolumetric relaxation? AV valves remain closed
What does the atrial blood pressure do during atrial relaxation and ventricular filling? forces AV valves open and blood flows into ventricles
What do the semilunar valves do during atrial relaxation and ventricular filling? Remain closed since arterial pressure is greater than ventricular pressure
Created by: elizabethcosio