Cardiac Cycle And Sounds Flashcards
When do the electrical events in the heart occur?
Before the mechanical event (contraction)
What is an electrocardiogram?
A recording of electrical events in the heart associated with the heartbeat
What is the P wave associated with?
Atrial depolarization and is usually initiated by the SA node
What is the PR interval?
The conduction velocity in the AV node is slow so there is a pause b/w the depolarization of the atria and that of the ventricles leading to this interval
What does the QRS complex represent?
Ventricular depolarization
What does the ST segment represent?
The time that the entire ventricle is in the plateau phase of the AP
What does the T wave indicate?
Ventricular repolarization and occurs before the actual relaxation of the ventricle
What are the different waves for the jugular pressure wave?
A, c and v waves
What is the a wave?
The pressure wave created by atrial contraction
Since there is no valve between the atria and great veins the pressure is reflected backwards
What is the c wave?
A pressure wave created by isovolumetric contraction of the ventricles
The AV valves which are closed bulge back into the atria creating an increase in pressure that is reflected backwards
What is the v wave?
A pressure wave created by blood returning back to the atria
Because the AV valves are closed the blood fills the atria and increases the atrial pressure
What is the first heart sound associated with?
Closure of the AV valves
What makes the first heart sound?
The sound is a result of blood in the atria hitting the closed valves as it tries to enter the ventricle
That impact creates vibration in the cardiac tissue that can be heard
What is the second heart sound associated with?
Closing of the pulmonary and aortic valves
Produces when the blood in the aorta/pulmonary A back flows and bounces off the closed valves
What creates the third heart sound?
The blood rushing into the ventricle during the rapid filling phase
Normal in children but may not be heard in normal adults unless conditions are right
Describe the 4th heart sound
May be heard during atrial contraction
It is the result of that last little bit of blood being squeezed into the ventricle
Normal in children but not generally heard in a normal adult
The four normal heart sounds are the result of what?
Blood moving in the expected directions
A murmur can be heard when either what occurs?
Blood is moving in a direction it shouldn’t be moving (regurgitation)
Blood is having a hard time moving in the direction it should be moving in (stenosis)
May be heard in systole or diastole
What is mitral regurgitation?
Regurgitation of blood back into the atria
What can cause a systolic murmur?
Mitral regurgitation
Stenosis of the aorta/pulmonary A not allowing blood to enter
What causes a diastolic murmur?
Aortic regurgitation
Blood not being able to move into the ventricles due to stenosis
What is aortic regurgitation?
Regurgitation of blood back from the aorta or pulmonary A into the ventricle
Review
Cardiac cycle
