10. Cardiac Cycle Flashcards
what do EKGs show
electical events of heart - depol/repol
*electrical event happens BEFORE mechanical event (contraction)
which wave is associated with atrial depolarization & where does it begin
P wave
initiated at the SA node
=atrial systole
what is the PR interval
SA –> AV
Av is slower so there is a lag of depol in ventricles after atria
-this allows atria to contract & max volume into ventricles before the ventricles contract
where is electical signal sent after the AV node
bundle of His –> R/L bundle banches –> purkinje fibers
what order does the ventricle depolarize
1.septum –> 2. walls of both ventricles starting from apex
this order produces efficient ejection of blood out to As
what does the QRS complex represent
ventricular depolarization
what is the T wave & when does it occur
ventricular repol
-occurs after QRS with lag inbtn - allows time for all cardiomyocytes to be depol - get Ca2+ to M & contract
what is the time it takes to get from one P wave to the next
less than 1 sec (0.8)
=around 60 bpm
when is ventricular P lowest
at diastole - to create pressure gradient for blood to be pushed from atria to ventricle
what happens to the ventricular P as you move from the P wave to the beginning of the QRS complex
increase slightly as the atria contracts
when does ventricular P increase significantly
QRS complex
ventricle depolarize
= isovolumetric contraction (all valves are closed) & peak after ejection begins
ventricles contract
what happens to ventricular P as ventricles repolarize (T-wave)
decrease
-ejecting blood out aortic/pul valve
what is diastolic blood pressure
= aortic pressure when aortic valve is open
aroudn 80 mmHg
reduced P bc blood leaving aorta
when does ventricular P drive aortic P
when ventricular P is above aortic and valves open to allow blood into aorta (same situation w/ pul valves)
aortic P follows ventricluar but slightly below
what is dicrotic notch
as the ventricles relax the ventircular P falls below aortic P & it diverges
aortic valve closes
what happens to the atrial P btn P & Q waves
atrial P increase slightly above ventricular P to create pressure gradient to force blood into ventricle
increase as th atria contract
what happens to atrial P during isovolumic ccontraction
atrial P increases
ventricles contracting - all valves are closed
what happens to atrial P when aortic/pul valves open
decreas quickly
-ventricle start ejecting blood
why does atrial P gradually increase as ventricular contraction continues
increase gradually bc of venous return
what happens to atrial P when AV valves open
atrial P decreases bc blood moves into ventricles
what is ideal ventricular volume & how much of it is ejected at the end of diastole
depends on age no idea
-usually eject 60-70% of volume (never gets to 0)
what happens to ventricular vol during the P wave
ventricular vol tops off
when does ventricular vol decrease rapidly
when aortic/pul valve open & blood rushes out into aorta & pul trunk
when is ventricular vol constant
isovolumetric contraction/relaxation
-all valves are closed
when does ventricular volume increase
AV valve open
rapid & then slow
what is the a-wave
atrial contraction
increase in jugular V pressure when atria contract after P wave - pressure reflected back to V
What happens to jugular p during isovolumetric contraction
increases
-all valves are closed
what is the c-wave
increase in P as the isovolumetric contraction in ventricles occurs (then decreases as aortic/pul valves open)
-bulging of the walls back into the atria
what is the v-wave
blood returning to atria & backing up into jugular V
ventricular contraction w/ AV valves closed but aortic/pul valves open
blood back to heart but cant enter ventricle
when does venous return occur
continously
what is the 1st heart sound
closing of the AV valves as centricles contract
what produces the 2nd heart sound
aortic/pul valve closing
what sound is present as the ventricles fill rapidly
3rd sound
heard in children (in adults with special stethescopes)
what is the sound that is due to blood entering ventricle during atrial contraction
4th sound
heard in children
when does ventricular systole happen
QRS to beyond T
-ventricular contraction
what happens in ventriclar diastole
ventricular relax
what happens to ventricular P as blood moves from atria to ventricles
increases
why is atrial pressure increasing during ventricular systole
blood continues to return to the heart but cant get into ventricle bc the AV valves are closed
what are two important things to note about aortic P
significantly above the atrial and ventricular P - a lot higher to allow efficient perfusion into body
it decreases throughout atrial contraction and even into ventricular contraction
when do AV valves close
when the ventricular P exceeds the atrial P
prevent back flow
what is normal aortic and pul A pressure
aortic P = 120/80
pul A P = 25/15
*ventricular P must EXCEED DIASTOLIC P on each side to open the valve
why does aortic P continue to drop throughout diastole
blood continues to leave aorta
peripheral run - off
what are causes of murmurs
blood moving backward (in direction it shouldnt)
- systolic murmur : mitral regurgitation
- diastolic murmur: aortic regurgitation
blood having hard time moving in the direction it should (stenosis)
