The Cardiac Cycle Flashcards
Define late diastole.
Both sets of chambers of the heart are relaxed and the ventricles are filling with blood.
What happens when the ventricles are filled with blood and the pacemaker cells reach threshold?
Depolarisation spreads through the atria leading to atrial contraction.
What happens in atrial systole?
Arterial contraction forces a small amount of additional blood into the ventricle.
Describe the pressure in the stage of atrial systole.
The pressure in the atria exceeds the pressure in the ventricles
What does the greater pressure in the atria lead to?
Causes the mitral and tricuspid valves to open.
What happens when the ventricles depolarise and contract?
Pulls the mitral and tricuspid valves shut.
What happens during the isovolumic ventricular contraction/the isometric contraction phase?
Left ventricular pressure to rise above atrial pressure, which closes the mitral valve and produces the first heart sound
What happens to the volume of blood in the isovolumic ventricular contraction/ isometric contraction phase?
Stays the same as the blood has nowhere to go as all the valves are shut
What happens to the ventricular pressure when all the valves are closed?
Ventricular pressure builds up until the pressure exceeds the pressure in the aorta and the pulmonary trunk, causing the aortic and pulmonary valves to open.
What happens in the ventricular ejection phase?
Blood is pumped out of the ventricle and into the aorta and pulmonary trunk
What happens to ventricular pressure as blood is pumped out?
Ventricular pressure drops
What happens when the ventricular pressure decreases beyond the pressure in the aorta and pulmonary trunk?
Aortic and pulmonary valves are pushed closed
What happens in the isovolumic ventricular relaxation phase?
Entry and exit valves are shut
Blood cannot leave
What happens as the atria begin to fill with blood?
Atrial pressure increases and gradually increases beyond ventricular pressure which pushes the mitral and tricuspid valves open and blood flows to the ventricles
Name the two divisions of the cycle.
Diastole and systole
What is the diastole stage known as?
Filling phase
What is the systole phase known as?
Ejection phase
At which point in the cardiac cycle is the systolic pressure?
Maximum pressure in the aorta
At which point in the cardiac cycle in the diastolic pressure?
Minimum pressure in the aorta during diastole
What is pulse pressure?
The difference between systolic and dystopic pressure
(systolic-dystolic)
What is MAP?
Mean arterial pressure
What value is MAP usually measured as?
One third between the diastolic and systolic pressures because two thirds are spent in diastole and one third of the cycle is spent in systole.
Rough estimate