Cardiac Cycle and Heart sounds Flashcards
What is important to realize in the EKG between the electric signals and mechanical signals
The electrical events in the heart associate with the heartbeat have to do with depolarization and repolarization
and these electrical events occur before the mechanical event of contraction
What is the P wave associated with
atrial depolarization
this is initiated by the SA node
this is also when the cardiac cycle begins
what is the PR interval associated with
the pause between the depolarization of the atria and the ventricles
this is because the conduction velocity in the AV node is slow
what is the order of the cardiac muscle depolarizing in the ventricles
this is done by the AV node transmitting the action potential
it will get the septum first to contract
the it will get the free walls of both ventricles starting from the apex back up
what does the QRS complex represent
Ventricular depolarization
the R wave is the first deflection upward after the P wave
What does the T-wave indicate
Ventricular repolarization
occurs before the actual relaxation of the ventricle
what is the name of the interval between the QRS complex and the T wave and what is happening
ST interval
period of zero potential between ventricular depolarization and repolarization
what is the a wave in regards to the jugular pressure
is the first bump
pressure wave created by the atrial contraction
since there is no valve between the atria and the great veins the pressure is reflected backwards
what is the c wave in regards to the jugular pressure
tallest peak
is the pressure wave created by the period of isovolumetric contraction in the ventricles
there is bulging of the wall back into the atria
what is the isovolumetric contraction
occurs in early systole when the ventricles contract but no volume change
this is because it is a short period where all heart valves are closed
what is the v wave in regards to the jugular pressure
long gradual increase after the c wave
it is the pressure wave created as blood returns back to the heart but cant go into the ventricle
what occurs during atrial contraction to atrial and ventricular pressure
start of the cardiac cycle
both the atrial and ventricular pressure begins to increase
atrial pressure slightly higher then ventricular pressure
why does the atrial pressure increase during ventricular systole
blood continues to return to the heart during the period of ventricular systole but cant move into the ventricles because of the ventricular contraction
this causes the atrial pressure to increase
what are the pressures in the left ventricle at the lowest and the highest
120mm/Hg over 0mm/Hg
how does the Aortic pressure behave during atrial contraction
the aortic pressure already sit way higher than the pressures in the atrium and the ventricle
during atrial contraction the pressure of the aorta decreases and will even continue to decrease as ventricular contraction begins due to isovolumetric contraction
After the atria contract and begin to relax what happens to the ventricle and what is this time period called
the ventricles immediately begin to contract and the pressure in the ventricles exceed the atrial pressure causing the AV valves to close preventing blood flow back into the atria
at this point the all valves are closed so the volume stays constant and the pressure increases (isovolumetric contraction)
when does blood eject from the ventricles into the aorta/pulmonary arteries
when the pressure in the ventricle exceeds the pressure in the pulmonary artery and aorta
what happens to the pressure of the aorta as the ventricular pressure exceeds the aortic pressure as the aortic valves open
the aortic pressure will then shoot up with the ventricular pressure and be ever so slightly below it
once the semilunar valves open this also ends the isovolumentric contraction phase
what happens to the ventricular volume when the semilunar valves open
it decreases rapidly as blood is ejected
how long does blood eject for
blood continues to be ejected until the pressure in the ventricle drops below the arterial pressure and the semilunar valves close
beginning Diastole
what happens to the aortic and ventricular pressure when diastole begins also how does this affect the atrial pressure
the aortic and ventricular pressures diverge since the semilunar valves are shut
the aortic pressure will slowly decreases
and the ventricular pressure will dramatically decrease
this separation of both pressures is called the dicrotic notch
this also shows a slight wiggle in the atrial pressure due to the closing of the valves
what event occurs after the closing of the semilunar valves
this small period after the closing of the semilunar valves is called the isovolumetric relaxation
it is the period where no blood enters or leaves the ventricle because both the AV and semilunar valves are closed
when does the AV valves reopen during ventricular diastole
once the ventricular pressure drops below the atrial pressure the AV valves will open
to note: blood will then move into the ventricles but the atria have not begun to contract at this point
how low does the pressures get into the ventricle to get blood to move into them from the atria
the ventricle pressure must be lower than the ventricles so the ventricle pressure can get all the way down to 0 mmHg
why does the the aortic pressure continue to drop throughout systole
the blood is leaving the aorta and flowwing into smaller vessels in the periphery
this rate of peripheral run off is determined by the resistance to blood flow
what is the first heart sound and how is it made
characterized by the lub and is associated with the closure of the AV valves
sound is a result of the blood hitting the closed valves in the atria as it tries to move into the ventricles
the impact creates a vibration in the tissue in the heart that makes a sound of lub
what is the second heart sound and how is it made
the second heart sound is associated with the closing of the aortic and pulmonary valves
produced when the blood in the aorta/pulmonary artery backflow bounces off the closed valves
this backflow is caused by the cut off of forward pressure and gravity pulling the blood back down
what is the third heart sound and how is it made
it is the blood rushing into the ventricle during rapid filling
this sound is normal in children but may be not heard in adults
what is the fourth heart sound and how is it made
heard during atrial contraction
it is the result of that last little bit of blood being squeezed into the ventricle
can be heard in children but not generally heard in adults
when is a murmur heard
blood is moving in a direction it shouldn’t be moving
blood is having a hard time moving in the direction it should be moving
murmurs can be heard in either systole or diastole and when they are heard gives you a clue to what the problem is
what are two causes of a systolic murmur
blood moving back into the atria caused by regurgitation (mitral regurgitation)
blood cant get pumped into the aorta/pulmonary artery due to a stenosis
what are the two causes of a diastolic murmur
blood moving back from the aorta/pulmonary artery/ into the ventricle caused by regurgitation (aortic regurgitation)
blood is having a hard time getting into the ventricle due to stenosis
