55 Questions
Which node initiates each cardiac cycle?
SA node
What is the duration of systole in relation to the total duration of the cardiac cycle?
1/3
What happens during systole?
The ventricles are developing force and ejecting blood
What is the duration of diastole in relation to the total duration of the cardiac cycle?
2/3
What happens during diastole?
The ventricles are relaxing and filling
What is directly affected when heart rate increases?
Diastasis
What is the volume of blood remaining in the ventricle at the end of ejection called?
End-systolic volume (ESV)
What is the equation for stroke volume (SV)?
SV = EDV - ESV
What is the equation for cardiac output (CO)?
CO = SV * HR
What is the ejection fraction (EF)?
The fraction or percentage of the blood that is ejected
Which side of the heart has pressures that are approximately one-fourth to one-fifth of the other side?
Right side
What is the volume of blood pumped by the heart per minute called?
Cardiac output (CO)
Which equation represents the length of the cardiac cycle?
cycle length (sec) = 60/HR
What is the term for the volume of blood ejected from the ventricle?
Stroke volume (SV)
Which fraction is used to calculate the ejection fraction?
SV/EDV
What does the ejection fraction (EF) measure?
The fraction of blood ejected from the ventricle
During isovolumic contraction, the volume of the left ventricle
remains constant
What happens at the start of ejection?
Aortic valve opens
What is the ejection fraction (EF) a measure of?
Percentage of blood ejected from the ventricle
What is the equation for ejection fraction (EF)?
EF = SV/EDV
What happens at the end of isovolumic contraction?
Aortic valve opens
What is the pressure within the left ventricle at the start of ejection?
Greater than aortic pressure
What is the stroke volume (SV)?
Volume of blood ejected from the ventricle in one cardiac cycle
What happens when the aortic valve closes?
Ejection ends
What happens during isovolumic relaxation?
Aortic valve closes
What is the pressure within the left ventricle at the start of ejection?
Approximately 100 mmHg
What happens during diastole?
Mitral valve opens
What is the volume of blood that fills the ventricle during atrial contraction?
15-20%
What is the term for the volume of blood ejected from the ventricle?
Stroke volume (SV)
What is the equation for cardiac output (CO)?
CO = SV x HR
Which wave is caused by filling of the atria during ventricular systole?
Atrial 'v' wave
What happens if an abnormal opening exists between the right heart and the left heart?
Blood flows from left to right
What is the function of the cardiac valves?
To produce unidirectional blood flow
How do the cardiac valve leaflets move?
They are moved primarily by the motion of the blood adjacent to their cusps
When do the valves open?
After a pressure gradient is established across them
What causes the leaflets of the valves to begin closing?
A retrograde flow of blood
What causes the final closing motions of the valves?
A retrograde flow of blood
What supports the atrioventricular valves when closed?
The chordae tendineae
How much blood can normal valves allow to flow in the retrograde direction?
1 to 2 ml
What happens when the valves are damaged or malformed?
They become insufficient (regurgitant)
Which wave is produced by the contraction of the atrium?
‘a’ wave
What causes the ‘c’ wave?
Bulging of the mitral valve leaflets
Which sound marks the start of systole?
S1
What causes the second heart sound (S2)?
Closure of the aortic and pulmonic valves
Which component of the second heart sound is associated with aortic valve closure?
A2
What happens to the A2-P2 interval during inspiration?
It increases
What is valvular stenosis?
Narrowing of the valve orifice
What is valvular insufficiency (regurgitation)?
Improper sealing of the valve
What can cause a murmur in valvular stenosis?
All of the above
What can cause a murmur in valvular insufficiency (regurgitation)?
Retrograde blood flow, which can be terublent
What is the interval between A2 and P2 called?
A2-P2 interval
Which sound of the second heart sound occurs first?
A2
Which sound marks the end of systole?
S2
What causes the first heart sound (S1)?
All of the above
Which component of the second heart sound (S2) is associated with pulmonic valve closure?
P2
Study Notes
Cardiac Cycle
- The sinoatrial (SA) node initiates each cardiac cycle
- Systole lasts for approximately 1/3 of the total duration of the cardiac cycle
- During systole, the ventricles contract, pumping blood out of the heart
- Diastole lasts for approximately 2/3 of the total duration of the cardiac cycle
- During diastole, the ventricles relax and fill with blood
Heart Rate and Stroke Volume
- When heart rate increases, the ejection fraction (EF) is directly affected
- The volume of blood remaining in the ventricle at the end of ejection is called the end-systolic volume (ESV)
- The equation for stroke volume (SV) is SV = EDV - ESV
- The equation for cardiac output (CO) is CO = SV x HR
Ejection Fraction and Cardiac Output
- Ejection fraction (EF) is the fraction of blood ejected from the ventricle with each beat
- EF is calculated using the equation EF = (SV / EDV) x 100
- EF measures the heart's pumping efficiency
- The left side of the heart has pressures that are approximately 4-5 times that of the right side
Cardiac Cycle Phases
- Isovolumic contraction occurs when the ventricle contracts without pumping blood out of the heart
- At the start of ejection, the pressure within the left ventricle exceeds the pressure in the aorta, causing the aortic valve to open
- At the end of isovolumic contraction, the aortic valve opens, and ejection begins
- During isovolumic relaxation, the ventricle relaxes without filling with blood
- The atrioventricular valves are supported by the chordae tendineae when closed
Valves and Blood Flow
- The cardiac valves prevent backflow of blood and ensure it flows in one direction
- The valve leaflets move passively in response to pressure changes
- The valves open when the pressure in the chamber exceeds the pressure on the other side of the valve
- The valves close when the pressure on the other side of the valve exceeds the pressure in the chamber
- Normal valves allow a small amount of backflow, but damaged or malformed valves can cause significant backflow
Heart Sounds and Valvular Problems
- The 'c' wave is produced by the contraction of the atrium
- The second heart sound (S2) is caused by the closure of the aortic and pulmonic valves
- The A2 component of the second heart sound is associated with aortic valve closure
- The P2 component of the second heart sound is associated with pulmonic valve closure
- Valvular stenosis is the narrowing of a valve, and valvular insufficiency (regurgitation) is the failure of a valve to close properly
- Murmurs can occur due to valvular stenosis or insufficiency
Test your knowledge of the cardiac cycle and its two main phases, systole and diastole. Learn about the duration of each phase and how they contribute to the overall heart rate.
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