Chapter 3 The Heart Pump Flashcards
Define a cardiac cycle
one complete sequence of cardiac filling, cardiac muscle excitation and contraction, with ejection of blood and then muscle relaxation (diastole and systole)
The diastolic phase begins with
the opening of the atrioventricular valves (AV)
What happen when the left ventricular pressure falls below left atrial pressure?
The mitral valve opens passively and the ventricle begins filling causing an initial drop in atrial pressure
During diastole, Proper filling of the ventricles depend on (3)
- the filling pressure of blood retuning to the heart and atria
- The ability of the AV valves to open fully (not be stenotic)
- the ability of the ventricular wall to expand passively with little resistance (compliance)
The P wave on an ECG coincides with
Depolarization of the atrial muscle cells
T/F: Atrial contraction is essential for adequate ventricular filling
Explain
False
the ventricle has nearly reached its maximum or EDV before atrial contractin begins
Describe what happens when atrial muscles contract?
near the end of ventricular diastole, atrial muscle cells develop tension and shorten, atrial pressure rises, and an additional amount of blood is forced into the ventricle
When does atrial contraction play a significant role?
- As HR increases; the time between beats shortens
- With ventricular stiffness (inc age/disease)
T/F: Throughout diastole, atrial and ventricular pressures are nearly identical
Explain
True
A normal open mitral valve has very little resistance to flow
When does ventricular systole begin?
When the action potential passes through the AV node and sweeps over the ventricular muscle
The QRS complex denotes
AP through the ventricles
During contraction of the ventricular muscle cells, where is pressure higher? What does this cause?
Ventricle
Abrupt closure of the AV valve
When does the aortic valve open?
When left ventricular pressure exceeds that in the aorta
What is the isovolumic phase?
Why is it named as such?
The period between mitral valve closure and aortic valve opening
During this interval, the ventricle is a closed chamber with a fixed volume
Describe the “rapid ejection period”
When the aortic valve opens, blood enters the aorta rapidly causing the pressure to rise. Pressure builds up simultaneously in both the ventricle and the aorta as the cells continue to contract
Peak systolic pressure describes
The maximum left ventricular and aortic pressures
Describe the differences in pressure of the left ventricle and the aorta during ejection
There is relatively no difference because the is little resistance to flow due to the size of the aortic valve orifice
What causes the aortic valve to close?
intraventricular pressure falls below aortic pressure
What is the cause of the dicrotic notch (incisura) in the aortic pressure tracing?
a small volume of aortic blood must flow backward to fill the space behind the aortic valve leaflets as they close
Describe what happens after aortic valve closure
intraventricular pressure falls rapidly due to relaxation of the ventricular muscle cells
T/F: atrial pressure progressively rises during ventricular systole
true
When does the ventricle reach its minimum or ESV?
At aortic valve closure
What is stroke volume
The amount of blood ejected from the ventricle during a single beat
Describe what happens to the aorta during systole
It distends because more blood enters than exits
What is the lowest aortic pressure called and when does it occur?
Arterial diastolic pressure
at the end of diastole
The difference between diastolic and peak systolic pressures is known as
pulse pressure
What portion of the cardiac cycle does the heart spend in diastole?
2/3
T/F: Both the right and left sides of the heart have identical stroke volumes
true
What is the major difference between the right and left heart pumps?
The magnitude of the peak systolic pressure; pressures on the right are considerably lower than the left
Typical pulmonary artery systolic and diastolic pressures?
24 mmHg
8mmHg
what is the jugular venous pulse?
the pressure pulsations that occur in the right atrium that are transmitted to the large veins near the heart
Describe c
The c wave coincides with the onset of ventricular systole and is caused by the bulging of the tricuspid valve into the right atrium; pressure falls after c because of atrial relaxation
Describe v
Right ventricular pressure increases behind a closed tricuspid valve with blood returning to the heart from the peripheral organs. Pressure falls after the tricuspid valve opens and blood moves into the relaxed ventricle
Describe a
produced by atrial contraction
Describe Heart sound S1
Where can it best be heard?
occurs at the beginning of systole because of the closure of the AV valves;
apex of the heart
Describe Heart sound S2
Where can it best be heard?
occurs from the closure of the aortic and pulmonic valves at the beginning of the period of isovolumetric relaxation
T/F: The aortic valve closes shortly after the pulmonic valve.
False; The pulmonic valve closes shortly after the aortic valve.
The discrepency in closure of aortic and pulmonic valves is enhanced during ?
What is the time range?
inspiration
30-60 ms
What are the 2 factors for prolonged ejection during inspiration?
- inspiration induced decrease in intrathoracic pressure and increased filling of the right side of the heart
- inspiration induced decrease in pulmonary vascular resistance
gallop rhythms include?
S3 and/or S4 heart sounds
What is the underlying basis for ventricular function?
cardiac muscle length-tension behavior
End diastolic ventricular pressure is referred to as? why?
ventricular preload
it sets the end-diastolic ventricular volume and therefore the resting length of the cardiac muscle cell fibers
systemic arterial pressure is referred to as? why?
ventricular afterload; it determines the tension that must be developed by cardiac muscle fibers before they can shorten
What are the 3 distinct influences on stroke volume?
contractility, preload, afterload
What effect does increased sympathetic activity have on stoke volume and contractility of the cardiac muscle?
increases both
How does increased arterial pressure affect stroke volume?
decreases stroke volume by increasing the afterload on cardiac muscle fibers
What effect does increased ventricular filling pressure have on stroke volume?
It increases end diastolic volume which increases SV, as per Starlings Law
