More heart stuff yayy :( Flashcards
What EXACTLY is the cardiac cycle
It is the coordinated and consistent contraction (systole) and relaxation (diastole) of the atrial and ventricular functional synctia
What is the total duration of the cardiac cycle
0.8 seconds
What are the different phases of cardiac cycle
- Phase of ventricular filling.
- Phase of atrial systole.
- Phase of isovolumetric contraction (ventricles contract)
- Phase of ventricular ejection.
- Phase of isovolumetric relaxation.
What happens in ventricular filling
- All 4 chambers diastole
- AV valves open
- Semilunar valves closed
- Blood enters via large veins into atria, into ventricles
- First 1/3 of phase= RAPID FILLING PHASE then filling speed decreases, DIASTASIS
Pressure in the ventricles is 0 mmHg
What happens in the phase of atrial systole
- SAN fires AP and causes atria to contract then to AVN
2, More blood enters ventricles
- pressure right= 4-6mmHg Left=7-8mmHg
The phase of atrial systole is reflected as what wave on the ECG
P wave
And PQ interval
What is the volume of blood that is contained in the ventricles at the end of diastole
End Diastolic Volume (EDV)
it is abt 130 ml
If theres no valves at the start of the atria, how does the blood not flow back into the venous vessels
Bc of circular muscle fibers that contract at the beginning of the Atrial systole
Directs blood to the AV valves
What is the pre ejection period divided into
Use left ventricle as example
Asynchronous= when tension starts to develop, not all the left ventricular cardiomyocytes are excited and the whole ventricle hasnt contracted yet Lasts until closure of mitral valve
Isovolumetric contraction= when mitral and aortic valve closed. The intraventricular volume DOES NOT change now
What happens in Phase of isovolumetric contraction
- ventricular pressure> atrial pressure so valves close
- Hear the first heart sound (S1) (closure of AV valves)
Phase of isovolumetric contraction (start of ventricular depolarization) is refelcted as what wav eon the ECG
Q wave
What triggers the ejection phase
When ventricular pressure reaches diastolic pressure of the large arterial vessels, causes the semilunar valves to open
What happens in the phase of ventricular ejection
- Stroken volum is ejected out of Aorta/ Pulmonary artery
- Pressure in arteries rech max systolic value
Aorta =125mmHg Pulmonary=25mmHg - Myocardial relaxation begins at the end of ventrcular repolarization
- Hear the 2nd heart sound (S2) when semilunar valves close due to drop in intraventricular pressure
Isovolumetric ejection (ventricular repolarization) is reflected as what wave on ECG
T wave
After ejection of stroke volume, what is left in ventricles
End systolic volume (ESV)
60 ml
What happens in the phase of isovolumetric relaxation
- Closure of semilunar valves (S2)
- Bc of semilunar valve closure, some blood returns to the heart then back to periphery
Ths causes small peak (on aortic oressure curve) called DICHROITIC WAVE
Detected by caraotid SPG
When does cardiac cycle begin again
When AV valves open due to interventricuao pressure being less than atrial pressure
ECG AND PCG
Records the ELECTRICAL activity of heart during cardiac cycle
Records the SOUNDS of the heart during cardiac cycle
How is pulse wave generated
By deformation of aortic wall during ventricykar systole
It is transmitted along arterial system
What does a carotid sphygmogram register
MECHANICAL OSCILLATIONS of arterial wall
WHat kind of sensor and where is the carotid sphygmogram placed
A piezelectric crystal is used placed on the RIGHT carotid artery
Elements of sphygmogram
Ao: reflects the opening of aortic valve.
(i) incisure: reflects aortic valve closure.
The P-wave on the anachoretic limb reflects
the maximum pressure in the aorta (systolic
presser).
T-wave (tidal wave), reflects the “summation”
of the pulse wave with reflected pulse waves
from the peripheral part of the vascular
system.
D-wave (dichroitic wave): reflects the blood
that returns to the heart and goes back again
to the periphery, after closer of semilunar
valves during diastole.
Where is the peripheral pulse curve (PPC) registered
These peripheral pulse oscillations from peripheral blood vessels are registered on one of the fingers or toes
What detects the oscillations in the peripheral blood vessels
pressure transducer indirectly senses volume change in the area
Why do we place the sensors for both sphygmogram and peripheral pulse curve on right side of body
Bc of BRACHIOCEPHALIC TRUNK
as thats where the rigt common carotid artery and right subclavian comes from
What is the main difference btw carotid SPG and PPC
In PPC, opening of aortic valve delayed bc it takes time for pulse wave to propagate to site of registration
Due to this phenomenon, the simultaneous
registration of SPG and PPC allows to determine
the velocity of pulse wave (PWV).
What determines the velocity of the Pulse wave
It increases w decreasing radius and increasig vessel wall thickness
PWV^2=Eh/2rρ
Where is pulse wave velocity lowest and highest
low= AORTA
high= ARTERIOLES
How to register linear blood velocity using Doppler flowmetry
Send ultrasonic waves
Relflected back by cells of blood
Leads to changing of frequency to hearing spectrum
3 main things that determine pre ejection period
preload (end diastolic volume)
yocardial contractility
Afterload (arterial pressure)
Duing isovolumetric period, how does the ventricle change
since some cardiomyocytes do change length (isotonic), ventricle:
Becomes more sphercal, circumference increases, base to apex distance decreases
When do the aortic valves open in isovolumetric contraction
when it reaches diastolic value of arterial presssure
Why do we have to work out central time for phase analysis of left ventricle
Delay of SPHYGMOGRAM compared to electrocardiogram and phonocardiogram
DELAY DUE TO time required for pulse ave to reach site of sphygmography recording
