Cardiac Cycle Flashcards
What is the cardiac cycle?
The sequence of events in 1 heartbeat
How is pressure made in the heart?
The myocardium contracts the generate pressure changes in the heart
In what directions does pressure go?
High to low pressure
What are the 3 main stages of the cardiac cycle?
Atrial systole
Ventricular systole
Diastole
What does systole mean?
Period of contraction
What does diastole mean?
Period of relaxation
What happens in the atrial systole?
Heart fills up with blood and ventricle relax
AV valves open
Semi lunar valves are closed
Both atria contract
Volume of atria decreases and pressure increases
Blood is forced into ventricles
What happens in the ventricular systole?
Atria relax
AV closes
Volume in ventricles decreases and pressure increases
Ventricles contract once full of blood
Forces blood into pulmonary artery and aorta
Semi lunar valve are open
What happens in the diastole?
Atria and ventricles relax
Pressure in ventricles is less than the atria pressure
Higher pressure blood in artery cause semi lunar valves to shut
Blood from the vena cava and pulmonary vein enter the atria
Blood trickles into the ventricles
AV and semilunar valves closed
What does myogenic mean?
A muscle that can initiate its own contractions on its own without the brain
What is the sino-atrial node for?
A small patch of tissue that secretes energy in a wave of excitation
How do atria contract?
The SAN sends a wave of excitation to the atria along the muscle tissue membranes, so the muscle contracts
What happens at the atria-ventricular node?
This is the route in which the wave of excitation uses to go to the ventricles
The wave has a delay to allow the atria to finish contracting and allow blood into the ventricles
What happened at the Bundle of His?
The waves go past the AVN down the Bundle of His to the hearts apex
How do ventricles contract?
At the apex a wave of excitation spreads over the ventricle walls so it contracts upwards and the blood goes up to the arteries
