Cardiac Cycle and Sounds Flashcards
When do the electrical events in the heart occur compared to the heart’s actual contraction?
BEFORE
The P wave is associated with?
Atrial depolarization
What initiates the P wave?
SA node
Describe the conduction velocity in the AV node
It is slower, so there is a pause between depolarization of the atria and ventricles
The slow conduction velocity of the AV node leads to what part of an EKG?
PR interval
Once the AV node transmits the action potential, where does it go?
- Down the interventricular septum
2. Then starting at the apex back up both ventricular walls
The QRS complex represents?
Ventricular depolarization
What does the ST segment represent?
Time the entire ventricle is in the plateau phase of the action potential
The 1st cell to depolarize in the heart is the ____ to repolarize and vice versa
LAST
The T wave indicates?
Ventricular repolarization
Ventricular repolarization (T wave) occurs when compared to actual ventricular relaxation?
BEFORE
Aortic pressure starts on a slow decline, what is the drop in pressure due to?
Peripheral run-off (blood moving into the periphery and away from aorta)
What determines how fast or how slow the aortic pressure declines?
TPR - total peripheral resistance
- How fast blood can move into periphery
If the TPR is HIGH, what will the aortic pressure decline show?
The blood movement will be SLOW, thus the decline in the aortic pressure will be SLOW too
Aortic pressure at its lowest point =
diastolic blood pressure
Aortic pressure at its highest point =
systolic blood pressure
When does the decline in the aortic pressure stop?
When the ventricular pressure rises enough to open the aortic valve and force blood into the aorta
At their peak, is ventricular or aortic pressure highest?
Ventricular pressure - needs to be in order to get blood to move into the aorta
As the aortic pressure declines towards the end of systole, there is a blip and it rises slightly. What causes that?
Closure of the aortic valve
Ventricular pressure and atrial pressure both begin very close to what value?
Zero
A wave of atrial pressure is due to?
Atrial contraction
C wave of atrial pressure is due to?
AV valve bulging into the atria during the ventricular isovolumetric contraction
V wave of atrial pressure is due to?
Venous return into the atria
What is the order of the atrial/jugular pressure waves?
ACV
What does the ventricular pressure have to be so that blood will flow into the ventricles from the atria?
LOWER than that pressure of the atria
Why does the jugular pressure curve look like the atrial pressure curve just slightly higher?
There is no valve between the jugular vein and atrium
To start the cardiac cycle, where is the ventricular volume?
Near its max, as blood has been filling the ventricles during diastole
With _____ there is a slight increase in ventricular volume
atrial contraction
During isovolumetric contraction, does the ventricular volume change?
No
Describe the valves during isovolumetric contraction?
AV valve and Aortic/Pulmonic valves both CLOSED
How low does the ventricular volume get?
NEVER 0 - usually around 50 mL left in the ventricles
When do the AV valves close?
After atrial contraction to prevent backflow into the atria
When will the Aortic/Pulmonic valves open?
Once the ventricular pressure EXCEEDS the pressure inside the aorta and pulmonary arteries
What is the period called when both valves are closed and the ventricles are depolarized and contracting but no blood is being ejected?
Isovolumetric contraction
When will the Aortic/Pulmonic valves close again?
Once the ventricular pressure drops below the aortic pressure
When does Isovolumetric relaxation begin?
When both valves are closed and the ventricle is relaxing and the pressure is dropping
When does Isovolumetric relaxation end?
When the ventricular pressure drops BELOW the atrial pressure and the AV valve opens
S1 heart sound
Closing of the AV valve at beginning of isovolumetric contraction
S2 heart sound
Closing of aortic/pulmonic valves @ di-crotic notch in aortic pressure wave
S3 heart sound
Period of rapid filling of ventricles
S4 heart sound
Blood forced in to the ventricle during atrial contraction
When will the S4 heart sound be heard?
Before S1!
During Diastole, describe the valves
AV valves open
Aortic/Pulmonic valves closed
– Ventricular pressure is lower than atrial pressure so blood flows directly into atria and into ventricles
With the P wave, which pressures slightly increase?
Atrial pressure due to contraction
Ventricular pressure due to increased blood moving in through AV valve
With the QRS complex, there is a slight increase in atrial pressure. Why?
Due to incoming blood (venous return) and due to the AV valve bulging back into atria
S1 heart sound
AV valves CLOSE to prevent backflow of blood from ventricles into atria
What causes the S1 heart sound to be heard?
Blood entering the atria now hits the closed AV valve and causes a vibration = “lub”
Isovolumetric contraction begins after which heart sound and describe the valves
After S1 when the AV valves and Aortic/pulmonic valves are CLOSED
Diastolic pressure
Lowest pressure recorded in the aorta/pulmonary artery just before the valves open
When will the aortic/pulmonic valves open?
When the ventricular pressure»_space; aorta/pulmonary artery pressure
When will the aortic/pulmonary valves close?
When the ventricular pressure «_space;aorta/pulmonary artery pressure
S2 heart sound
Aortic/pulmonic valves CLOSE
“dub”
What causes the S2 heart sound to be heard?
Blood moves backwards in the artery and hits valve to cause vibration since the pressure from the ventricle is cut off abruptly with the closure of the valves
What causes the dicrotic notch in the aortic pressure wave and a similar wiggle in the atrial pressure wave?
Closure of the Aortic valve
When does Isovolumetric relaxation begin?
When both valves are closed and the ventricle is relaxing while the pressure is dropping
When does Isovolumetric relaxation end?
When the Ventricular pressure drops below the atrial pressure and the AV valves open
S3 heart sound
Rapid filling of the ventricles
When is the S3 heart sound heard?
Immediately after S2
S3 and S4 heart sounds are more often heard in?
Children due to thin body wall
Regurgitation
Blood is going in a direction it should NOT be going
Stenosis
Blood is going in the right direction but is having a hard time getting there
Valve unable to close or stay closed causes?
Regurgitation
Narrowing of valve or it doesn’t open fully causes?
Stenosis
When are systolic murmurs heard?
Between S1 and S2 - lub dub
With a systolic murmur, where could regurgitation take place?
AV valve
With a systolic murmur, where could stenosis take place?
Aortic/pulmonic valves
When are diastolic murmurs heard?
After S2
With a diastolic murmur, where could regurgitation take place?
Aortic/pulmonic valves
With a diastolic murmur, where could stenosis take place?
AV valves
The ventricular pressure must exceed what pressure in the aorta and pulmonary artery in order to open the valves?
Diastolic pressure