Cardiac Cycle and Heart sounds

Question 1

What is important to realize in the EKG between the electric signals and mechanical signals

Answer 1

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

Question 2

What is the P wave associated with

Answer 2

atrial depolarization

this is initiated by the SA node

this is also when the cardiac cycle begins

Question 3

what is the PR interval associated with

Answer 3

the pause between the depolarization of the atria and the ventricles

this is because the conduction velocity in the AV node is slow

Question 4

what is the order of the cardiac muscle depolarizing in the ventricles

Answer 4

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

Question 5

what does the QRS complex represent

Answer 5

Ventricular depolarization

the R wave is the first deflection upward after the P wave

Question 6

What does the T-wave indicate

Answer 6

Ventricular repolarization

occurs before the actual relaxation of the ventricle

Question 7

what is the name of the interval between the QRS complex and the T wave and what is happening

Answer 7

ST interval

period of zero potential between ventricular depolarization and repolarization

Question 8

what is the a wave in regards to the jugular pressure

Answer 8

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

Question 9

what is the c wave in regards to the jugular pressure

Answer 9

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

Question 10

what is the isovolumetric contraction

Answer 10

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

Question 11

what is the v wave in regards to the jugular pressure

Answer 11

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

Question 12

what occurs during atrial contraction to atrial and ventricular pressure

Answer 12

start of the cardiac cycle

both the atrial and ventricular pressure begins to increase

atrial pressure slightly higher then ventricular pressure

Question 13

why does the atrial pressure increase during ventricular systole

Answer 13

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

Question 14

what are the pressures in the left ventricle at the lowest and the highest

Answer 14

120mm/Hg over 0mm/Hg

Question 15

how does the Aortic pressure behave during atrial contraction

Answer 15

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

Question 16

After the atria contract and begin to relax what happens to the ventricle and what is this time period called

Answer 16

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)

Question 17

when does blood eject from the ventricles into the aorta/pulmonary arteries

Answer 17

when the pressure in the ventricle exceeds the pressure in the pulmonary artery and aorta

Question 18

what happens to the pressure of the aorta as the ventricular pressure exceeds the aortic pressure as the aortic valves open

Answer 18

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

Question 19

what happens to the ventricular volume when the semilunar valves open

Answer 19

it decreases rapidly as blood is ejected

Question 20

how long does blood eject for

Answer 20

blood continues to be ejected until the pressure in the ventricle drops below the arterial pressure and the semilunar valves close

beginning Diastole

Question 21

what happens to the aortic and ventricular pressure when diastole begins also how does this affect the atrial pressure

Answer 21

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

Question 22

what event occurs after the closing of the semilunar valves

Answer 22

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

Question 23

when does the AV valves reopen during ventricular diastole

Answer 23

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

Question 24

how low does the pressures get into the ventricle to get blood to move into them from the atria

Answer 24

the ventricle pressure must be lower than the ventricles so the ventricle pressure can get all the way down to 0 mmHg

Question 25

why does the the aortic pressure continue to drop throughout systole

Answer 25

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

Question 26

what is the first heart sound and how is it made

Answer 26

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

Question 27

what is the second heart sound and how is it made

Answer 27

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

Question 28

what is the third heart sound and how is it made

Answer 28

it is the blood rushing into the ventricle during rapid filling

this sound is normal in children but may be not heard in adults

Question 29

what is the fourth heart sound and how is it made

Answer 29

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

Question 30

when is a murmur heard

Answer 30

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

Question 31

what are two causes of a systolic murmur

Answer 31

blood moving back into the atria caused by regurgitation (mitral regurgitation)

blood cant get pumped into the aorta/pulmonary artery due to a stenosis

Question 32

what are the two causes of a diastolic murmur

Answer 32

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