Lectures 14 & 15: Cardiac Cycle/ pumping action of the heart Flashcards
How would aortic stenosis affect afterload?
increase it
What effect does increased afterload have on SV?
decreases it
How will an increase in afterload affect ESV (end systolic volume)?
increase
In order to increase contractility (aka ionotropy), does there have to be an increase in EDV?
No
What happens when the atria do contract?
They push more blood into ventricles. (10-40% of blood)
When the AV valves are open, most blood returning to the atria pass right through to the ___________. (60-90% of blood)
ventricles
Atria function to enhance _______________, which enhances _______________.
the amount of blood in ventricles; ventricular pumping
Can the heart function without atrial contraction?
Yes.
What is the function of the ventricles?
to pump blood through pulmonary circulation (right) and systemic circulation (left)
Valves open and close __________.
Passively
Forward pressure gradient _______ valves.
opens
Backward pressure gradient _______ valves.
closes
What does the papillary muscle of the AV valves do?
it prevents cusps from protruding into the atria as the ventricles contract
What happens if you have damage to chordae tendinae or papillary muscle?
You will get backward flow of blood as the ventricles contract & this could be lethal
Do Semilunar valves have chordae tendinae or papillary muscles?
No!!!
What does the cardiac cycle refer to?
the sequence of events (electrical & mechanical) occurring in the heart during a single beat
Referring to the cardiac cycle, do the same events occur on the right side of the heart as on the left side?
Yes, almost simultaneously
What are the 5 phases of the cardiac cycle?
- atrial contraction
- period of isovolumetric contraction
- period of ejection
- period of isovolumetric relaxation
- ventricular filling
What happens during atrial contraction?
The AV valve is open and the atrium pumps blood into the ventricle
When does the AV valve close?
once the pressure in the ventricle exceeds the pressure in the atrium
The period of contraction while the AV valve and semilunar valve are closed is the __________________.
isovolumetric contraction phase
When does the semilunar valve open during the period of isovolumetric contraction?
once the pressure in the ventricle exceeds the pressure in the aorta (arterial pressure)
When the semilunar valve opens (in the period of isovolumetric contraction)… what phase does this lead to?
the ejection phase
What happens in the period of ejection?
As ventricular pressure rises above arterial pressure, semilunar valve opens and blood is ejected out of ventricles.
During the period of isovolumetric relaxation, what happens to the pressure within the ventricle?
it begins to drop
During the period of isovolumetric relaxation, what causes the semilunar valves to close?
when the pressure drops below arterial pressure
The period of relaxation while both the AV valves and semilunar valves are closed is the _____________________.
isovolumetric relaxation phase
During the isovolumetric relaxation phase, ventricles continue to relax and eventually what happens?
The pressure drops below that of the atrium and therefore the AV valve opens leading to the ventricular filing phase
What happens during the ventricular filling phase?
passive filling of ventricle
Define systole
contraction phase of cardiac cycle
Define diastole
relaxation phase of the cardiac cycle
Define systolic blood pressure
the pressure in the systemic arteries (aorta) while the left ventricle is contracting and ejecting blood (120mmHg)
Define diastolic blood pressure
the pressure in the systemic arteries (aorta) while the left ventricle is relaxing and NOT ejecting blood (80mmHg)
What does EDV stand for?
End diastolic volume
Define EDV and the amount.
volume of blood in the ventricle at the end of diastole OR the amount of blood in the ventricle before it contracts
(amount= 110mL)
What is an important determinant of EDV?
venous return
What does ESV stand for?
end systolic volume
Define ESV and the amount.
the volume of blood in the ventricle at the end of systole (amount =40mL)
What does SV stand for?
stroke volume
Define SV and the amount.
the volume of blood pumped out of the left ventricle per contraction (amount= 70mL)
What is SV determined by?
Preload, afterload, and contractility.
What is ejection fraction?
The fraction of EDV that was pumped out of the left ventricle per contraction (60%)
What is the formula for EF?
SV/EDV x 100 = EF
Define cardiac output (CO, Q)
the amount of blood pumped out of the left ventricle per minute
What is the formula for cardiac output?
CO= HR x Stroke volume (5000mL)
Define venous return
the amount of blood returned to the heart
Define preload
The pressure stretching the chamber of the heart before it contracts (the stretched state of the ventricle before it contracts)
The greater the stretch, the _______ the preload.
greater
Preload is determined primarily by what?
EDV
Define afterload
the pressure that the chamber of the heart has to overcome in order to eject blood
What is an important determinant of the afterload of the LEFT ventricle?
aortic pressure
What is an important determinant of the afterload of the RIGHT ventricle?
pulmonary pressure
As aortic pressure increases (systemic HTN), the left ventricle has to produce _____ pressures and work harder in order to eject blood into the aorta against that higher pressure.
higher
As the aortic pressure (arterial pressure) increases, what happens to the afterload of the left ventricle?
It also increases
What is contractility also called?
Inotropy
What is contractility?
the intrinsic ability of cardiac muscle to produce tension (independent of fiber/sacromere length)
If there’s a change in the force of contraction at a constant end-diastolic fiber length, what will happen?
There will be a change in the contractility
Anything that affects excitation-contraction, other than sacromere/fiber length, affects ____________.
Contractility
What is an important determinant of contractility?
Intracellular Ca2+ concentration
Under normal physiological conditions, what is it that will alter contractility throughout the day?
the changing intracellular Ca2+
What will stimulate an increase in intracellular Ca2+ concentrations in cardiomyocytes and lead to an increase in contractility?
Norepinephrine (SNS)fer4gth1
Define Chronotopic effect
affecting heart rate
Define Inotropic effect
affecting contracility
What is the cardiac reserve?
The work that the heart is able to perform beyond what’s required of it under basal/resting conditions (300-400%)
Define pressure rate product or double product
an indirect index of myocardial O2 consumption (how hard the ventricle is working)
What is the formula for pressure rate product?
HR x SBP (or MAP)
What does S1 represent?
closing of AV vavles
What does S2 represent?
closing of semilunar valves
The presence of S3 or S4 may be indicative of what?
an abnormality
S3 is thought to be caused by what?
the oscillation of blood back and forth between the walls of the ventricles initiated by inrushing blood from the atria (increased volume of blood within the ventricle; may be associated with ventricular dilation)
What exactly is S3?
vibrations during rapid phase of ventricular filling
When might you hear S4?
during atrial contraction or when atrial pressure is high or ventricle is stiff
What does hypertrophy cause?
stiffening of the ventricle
