Phys Lecture 2: Cardiac Cycle Flashcards
When atrial pressure is greater than ventricle pressure, the AV valve will be (open or closed)
open
What prevents regurgitation of blood from the ventricle back into the atria?
closure of AV valves
When the left ventricular pressure is less than the aortic pressure the aortic valve is (open or closed)
closed
*this also prevent regurgitation
What initiates the cardiac cyle?
electrical signal that depolarizes atria/SA node
What is the P wave?
atrial depolarization
What is the QRS complex?
ventricular depolarization
What is the T wave?
ventricular repolarization
Why is the P wave smaller than the QRS?
atria has less mass and slower conduction
than the ventricles
At what part of the ventricle’s cardiac cycle does the pressure reach its peak?
reducted ejection
T or F: When blood is ejected from the left ventricle to the aorta, the pressure in the L ventricle is always higher than in the aorta
F: you may think that this would be true in order to keep the aortic valve open, but in reality it may not be. However, the blood is moving and therefore has more momentum and more total energy than the the aorta = keep the blood flowing from ventricle to aorta (and valve open)
T or F: Aortic pressure never fall rapidly (in health)
T (bc aorta always has blood in it)
What causes retrograde flow in the aorta? Why would this happen?
recoil from muscle cells after ventricular relaxation
helps to close the aortic valve
When do the atria fill with blood?
during ventricular systole
T ot F: the second heart sound is more prolonged than the first
F: the first is more prolonged than the first
What generates the frist heart sound?
vibration of blood in ventricles following closure of AV valves (NOT the actual closure of the valves)
How does S1 compare to S2?
lower pitched, more intense and longer
What generates the 2nd heart sound?
oscillation of blood in aorta and pulmonary arteries following closure of aortic and pulmonary valves
What generates the 3rd heart sound?
during early diastole, vibration of blood during ventricular filling
**more intense in heart failure
When does the 4th heart sound occur?
during atrial contraction and is low in intesity and pitch
If ventricles become stiffened (loss of compliance), which heart sound becomes more prominent?
S3 (due to vibration of blood in ventricles during ventricular filling = diastolic sound)
Work of heart =
pressure X volume
W = PV
What is EDV?
preload!
volume of filled ventricles (right before ejection/contraction)
What is preload?
pressure at the end of diastole
EDV or the volume of blood in the ventricles right before it is ejected
What is afterload?
the pressure the ventricles must create to open the aortic valve
*pressure is caused by volume
What is systolic pressure?
peak pressure in the AORTA
What is diastolic pressure?
minimum pressure in the AORTA
How does increase in preload affect SV and systolic pressure?
it increases SV
Why will a change in afterload affect SV?
increasing the pressure that the ventricle must create/pump causes inc resistance that the pump has to work against (W=PV) –> a slower contraction = less blood pumped (not all pumped out before next contraction/AP?)
What effect on SV and systolic pressure does decreasing the preload have?
dec SV and dec systolic pressure
What effect does inc afterload have on SV and systolic pressure?
dec SV and inc systolic pressure
What effect does dec afterload have on SV and systolic pressure
inc SV and dec systolic pressure
How can contractility be increased?
decrease?
inc sympathetic activity = inc Ca = inc contraction
intracell
withdrawal sympathetic activity or inc parasympathetic activity
What effect on SV and systolic pressure does an inc in contractility cause
inc SV and inc SP
How can the heart compensate for an increase in afterload? (2)
- increase contractility
- inc preload
*maintains SV = maintains CO
