7.5- THE CARDIAC CYCLE Flashcards
How many times does the human heart undergo a sequence of events each minute when at rest?
sequence of events that’s repeated around 70 times each minutes when at rest
What is the sequence of events that the heart undergoes called?
cardiac cycle
What are the two phases to the beating of the heart?
contraction (systole)
relaxation (diastole)
How does contraction occur separately?
occurs separately in ventricles + atria
As contractions occurs separately in ventricles + atria, how many stages is it described in?
in two stages
For some of the time, how does relaxation take place?
relaxation takes place simultaneously in all chambers of heart
Through where does blood return to the atria of the heart? (2) (diastole)
through pulmonary vein (from lungs) vena cava (from body)
What rises as the atria fill? (diastole)
as atria fill, pressure in them rises
What happens when the pressure in the atria exceeds that in the ventricles? (diastole)
atrioventricular valves open allowing blood to pass into ventricles
What is the passage of blood from atria to ventricles aided by? (diastole)
aided by gravity
When blood passes from the atria to ventricles, how are the muscular walls of the atria + ventricles? (diastole)
muscular walls of atria + ventricles relaxed at this stage
What does the relaxation of the ventricle walls cause? (diastole)
causes them to recoil + reduces pressure within the ventricles
When the ventricle walls relax + reduces pressure within the ventricles, what is the pressure in the ventricles like in comparison to that in the aorta + pulmonary artery? (diastole)
pressure lower than in the aorta + pulmonary artery
As the pressure in the aorta + pulmonary artery is higher when the muscular walls of ventricles relax, what happens? (diastole)
semi-lunar valves in aorta + pulmonary artery closes, accompanied by characteristic ‘dub’ sound of heart beat
What forces the remaining blood into the ventricles from the atria, after diastole? (atria systole)
contraction of atrial walls, along with recoil of relaxed ventricle walls
How are the muscle of the ventricle walls throughout this stage? (atria systole)
throughout this stage muscle of ventricle walls remains relaxed
Why is there a short delay after atrial systole? (ventricular systole)
to allow ventricles to fill with blood
What happens after the short delay to allow ventricles to fill with blood? (ventricular systole)
ventricle walls contract simultaneously
What happens when the ventricle walls contract simultaneously? (ventricular systole)
increases blood pressure within them, forcing them to shut atrioventricular valves + preventing backflow of blood into atria
What is the ‘lub’ characteristic of the heart beat? (ventricular systole)
valves closing