7. Cardiac Cycle and Sounds Flashcards
Atrial systole occurs from the P wave until QRS. When do ventricular systole and diastole occur?
Ventricular systole: from QRS to T wave
Ventricular diastole: after T wave (to P wave?)
What kind of contraction occurs during ventricular systole?
Ventricular contraction
The typical aortic pressure is 120/ 80. The typical ventricular pressure is 120/0 and what is the typical ventricular volume?
Peak volume is 120ml and lowest volume is 50 ml
Since atria depolarize first, they contract first which increases?
the pressure in the atria
As the atria pressure increases due to contraction, the ventricular pressure increases because?
blood is pushed from atria into the ventricles
- ventricular pressure less than atrial to drive blood from A to V
After the atria contracts and begins to relax, the ventricles start to contract, what is the pause during AV nodes significance?
It gives the atria time to do their job before the ventricles contract
The walls of the ventricles contract next squeezing the blood in the chambers which increases the pressure. What is the drop in pressure before ventricular pressure dramatically increases?
The AV valves are closed
QRS is the sum of all phase 0 ventricular myocytes
Why does the atrial pressure increase during ventricular systole?
Blood continues to return to the heart during the period of ventricular systole, but can’t move into the ventricles because of the ventricular contraction, causing ATRIAL pressure to increase
During ventricular diastole, (Phase 3-T wave: K+ leaves cell, repolarizing, Ca2+ leaves cell), the relaxation of the ventricle begins which causes?
A decrease in the ventricular pressure
The lowest and highest pressure in the ventricle are 120mmHg and 0mmHg. What occurs at the ST segment and end of systole?
ST segment: highest ventricle pressure and end of systole is lowest ventricle pressure
In diastole atrial pressure exceeds ventricular pressure, during systole ventricular pressure greatly exceeds the atrial pressure. During ventricular contraction…?
Atrial pressure increases as blood returns
During diastole, neither atrial or ventricle are contracting see small increase as blood returns.
The pressure in the atria exceed that in the ventricle and forces the blood in the atria to move into the ventricle during atrial systole. So what increases as atrial contraction forces blood into the ventricle?
Ventricular volume
What are two important things to note about the aortic pressure?
- The aortic pressure is above the atrial and ventricular pressures
- It is decreasing throughout the atrial contraction and even into ventricular contraction
As ventricles start to contract in systole, the ventricular pressure exceeds the atrial pressure… causing?
AV valves to close, preventing blood from flowing back into the atria. Which during the aortic presure falls while ventricular volume is constant.
Contraction of the ventricles builds pressure in the ventricles, is any blood being ejected?
No the pressure in the ventricle must exceed the pressure in the pulmonary artery and aorta before the valves (semilunar) leaving the ventricles will open
What occurs during isovolumetric contraction?
Ventricular volume remains constant while ventricular pressure increases dramatically (upright slope)
Which number, diastolic or systolic dictates how hard the left ventricle needs to squeeze to open the aortic valve?
the diastolic number
What pressure does the L/R ventricle have to reach/EXCEED before the semilunar valves open?
On right side, pulmonary pressure is 25/15 and on the left side, aortic pressure is 120/70-80. So 15 on the right and a pressure of 70-80 on the left
Once the ventricular pressure exceeds the aortic pressure, the aortic valves open and blood is ejected from the ventricle. What does this end?
Once LV pressure exceeds aortic pressure, the isovolumetric contraction ends. (V pressure just a little larger than A pressure)
What decreases as the pressure in the ventricle and aorta increase?
The volume in the ventricle because it is going into the aorta!
Aortic pressure starts to decrease even as blood continues to be ejected as the rate of ejection slows down. Along with ventricular pressure, what also continues to decrease during this time?
Ventricular Volume
When the pressure in the ventricle drops below the arterial pressure, the aortic and pulmonary valves____?
CLOSE! (semilunar) (ventricular diastole)
When the aortic valve closes, the aortic pressure and ventricular pressures diverge. The ventricular pressure decreases rapidly and the aortic pressure?
produces the dicrotic notch remaining much higher in pressure
Once the semilunar valves close, ‘we’ enter a period in which no blood enters or leaves the ventricle while it is relaxing because both AV and semilunar valves are closed. What occurs during this time when all four valves are closed?
Isovolumetric relaxation!
Once the ventricular pressure decreases to be less than atrail pressures after the semilunar valves close, what occurs?
When atrial pressure is greater than ventricular pressure, the AV valves will open and blood will move from the atria to the ventricles (ventricular diastole)
atria are not contracting at this point
What pressure do the L and R ventricles have to be at for the blood to enter from the atria?
Ventricular pressure must be lower than all other pressures during diastole for blood to move from high pressure to low pressure
As blood flows rapidly back into the ventricles, the aortic pressure…?
continues to drop and will do so throughout diastole
Why does the aortic pressure still drop?
Blood leaves the aorta goes into peripheral run off, the rate is determined by resistance to blood flow
What does the A wave of the jugular pressure signify?
The pressure wave created by atrial contraction (atria contract and push blood back into jugular vein, increasing pressure slightly)
What does the C wave of the jugular pressure signify?
The pressure wave created by the period of isovolumetric contraction in the ventricles (highest jugular P at this time)
What does the V wave of the jugular pressure signify?
The pressure wave as blood returns back to the heart but can’t enter ventricle
What preceeds all the mechanical events of the cardiac cycle?
The electrical activity
What produces the PR interval in an ECG?
The conduction velocity in the AV node is slow, so there is a pause between the depolarization of the atria and that of the ventricle
When the AV node transmits the AP to the bundle branches and purkinje fibers, they transmit the AP to the ventricle depolarizing the? (2)
Septum and free walls of both ventricles starting from the apex back up (QRS complex!)
The time delay between QRS and the increase in ventricular pressure is due to?
the time it takes to begin contraction (QRS begins before ventricular pressure begins to increase)
What occurs during the entirety of the ST segment and QT interval?
ventricular contraction
The Twave (indicative of repolarization) will be inscribed prior to the actual relaxation of the ventricle (top of ventricular pressure arch). Remember: ventricular pressure starts to fall as the blood is ejected from the ventricle so the decline in pressure leads to…?
relaxation of the ventricles
The first sound is associated with the closure of the AV valves. What makes this sound?
A result of the blood in the atria hitting the closed valves as it tries to enter the ventricle. (creates vibration in cardiac tissue)
The second heart sound is associated with the closing of the aortic and pulmonary valves. What makes this sound?
Produced when the blood in the aorta/pulmonary artery backflows and bounces off the closed valves
Why does blood back flow into the closed valves?
The force driving the blood forward (ventricular pressure) is cutoff from the blood and gravity is free to pull the blood back down
What creates the third NORMAL heart sound that can be heart more in children than adults (can be abnormal if heard in adults)? occurs after S2
The sound comes from the blood rushing into the ventricle during the rapid filling phase
What is the results of the fourth heart sound that can be heard during atrial contraction? Occurs before S1
From the last little bit of blood being squeezed into the ventricle; normal in children not heard in normal adults
What are the two conditions in which a murmur is heard, which can be heard in either sytole or diastole?
- blood is moving in a direction it should not be moving
2. Blood is having a hard time moving in the direction it should be moving in
A ventricular systolic murmur can either be cause by blood moving back into the atria caused by mitral regurgitation, or it can be caused by?
caused by the inability of blood to get into the aorta/pulmonary arteries due to stenosis
PRESENTS AS WOOSHING SOUND BETWEEN S1 & S2
A ventricular diastolic murmur can be heard by either aortic regurgitation (blood flowing back into ventricle) or by?
The blood not being able to get into the ventricle caused by stenosis
PRESENTS AS WOOSHING AFTER S2
