Cardiac cycle Flashcards
What is the diastole?
heart relaxes
atria and then the ventricles fill with blood
the volume and pressure of the blood in the heart build as the heart fills
pressure in the arteries is at its minimum
What is systole?
atria contract (atrial systole) closely followed by the ventricles
pressure inside the heart increases dramatically and the blood is forced out of the heart
the volume and pressure of the blood in the heart are low at the end of systole and blood pressure in the arteries is at a maximum
Descirbe the pressure insid the atria?
always relatively low because its thin walls cannot create mich force
highest when they are contracting but drops when the atrioventricular valve closes and its walls relax
the atria then fills with blood which leads to a gradual build up of pressure until a slight drop when the left atrioventricular valve opens and some blood moves into the ventricles
Describe the aortic pressure
rises when the ventricles contract as blood is forced into the aorta
it then gradually falls
never below 12 kPa
at the start of the relaxation phase the elastic walls creates a recoil and produces a temporary rise in pressure
Describe ventricular pressure
low at first but gradually increases as the ventricles fill with blood and the atria contract
the atrioventricular valves close and pressure rise dramatically as the thick muscular walls of the ventricles contract
as pressure rises above that of the aorta, blood is forced into the arteries
pressure falls as the ventricles empty and the walls relax
Describe ventricular volume
rises as the atria contract and the ventricles fill with blood
suddenly drop as blood is forced into the arteries when the semilunar valve opens
volume increases again as the ventricles fill with blood
What causes the noises heart by the stethoscope?
closing of the heart valves
the first ‘lub’ sound comes as the blood is forced against the atrioventricular valves as a backflow of blood as the ventricles contract
the ‘dub’ sounds comes as a backflow of blood closes the semilunar valves in the arteries as the ventricles contract
when does the atrioventricular valve open
after the ventricles have finished contracting
leads ti decrease in pressure and vol of blood in atria
