Lecture 10: Cardiac Cycle and Heart Sounds Flashcards
Describe the P wave.
Start of cardiac cycle: Atrial depolarization
-initiated by SA node
Describe the PR interval.
Pause between atrial and ventricular depolarization
-imp so ventricles can be filled w/ blood before ejection
How are ventricles depolarized?
First the septum to the apex of the heart. Then it goes back up along the side of the ventricular walls.
- Most efficient way to eject blood into pulmonary artery or aorta
- depolarization done by bundle branches and purkinje fibers
Describe the QRS complex.
Ventricular depolarization
-takes time for ventricular pressure to increase and ventricles to begin contraction
Describe the T wave.
Ventricular repolarization
Between the QRS complex and T wave, what is the state of the ventricular myocytes?
Ventricular myocytes are depolarized
When does the mitral valve open?
When atrial pressure is higher then ventricular pressure
When does the aortic valve open?
When ventricular pressure is higher then aortic pressure
What is systole?
Phase of cardiac cycle when the heart contracts and pumps blood from the ventricles into the aorta
–isovolumetric contraction to beginning of isovolumetric relaxation
What is diastole?
Phase of the cardiac cycle when the heart muscle relaxes and allows the chambers to fill with blood
What does jugular pressure measure?
Pressure in internal jugular vein that indirectly can tell the pressure of the right atrium
Describe the a wave in the jugular pressure wave.
Atrial contraction
Describe the c wave in the jugular pressure wave.
Isovolumetric contraction in ventricles
- all valves are closed
- pressure building in ventricles
Describe the v wave in the jugular pressure wave.
Ventricular contraction
- AV valve is closed
- blood filling atria
Why is atrial pressure increasing during ventricular systole?
Atria is filling while AV valves are closed, causing atrial pressure to increase
What is the dicrotic notch?
After the aortic valve closes, there is a notch in the aortic pressure wave that looks like a wiggle. It signifies the closing of the valve.
What is the first heart sound ‘lub’ associated with?
Closure of AV valves
-sound is from blood entering atria and hitting closed valve trying to get to ventricle
What is the second heart sound ‘dub’ associated with?
Closing of semilunar (aortic and pulmonary) valves
-sound is from blood in aorta and pulmonary artery trying to go backward and hitting closed valve
What is the third heart sound associated with?
Rapid filling of ventricles
- normally heard in children
- normal in adults but not common
What is the fourth heart sound associated with?
Topping of ventricle during atrial contraction
-normally heard in children
What can cause a murmur?
Blood moving in the wrong direction
Blood having a hard time moving in the right direction
What can cause a systolic murmur?
Blood moving back into atria from ventricles
Blood cannot get into aorta or pulmonary artery due to stenosis
What can cause a diastolic murmur?
Blood moving back into ventricle from aorta or pulmonary artery
Blood cannot get into ventricle due to stenosis
