Download The Systolic phase

Lecture 3 - 3/7/2013
Cardiac output: is the blood volume heart ejected from the (left ventricle
or the right ventricle) per minute.
 Cardiac output changes due to the intensity of exercises we do. increasing
intensity of exercises increases oxygen the body needs , with the result that
increase in cardiac output
Volume of blood that heart ejects per minute:
During rest 5 l/min, during light exercises10 l/min, during moderate exercises 15
l/min, and during severe exercise 20 l/min.
 If the volume of blood which ejected by heart is not enough to provide the cells
with oxygen they need this means a heart failure which causes hypoxia.
Symptoms of heart failure:
1- Dyspnea
2- Fatigability (fatigue)
3- Palpitation
Heart failure classified into four stages –according to the cardiac output-
1- Stage 1 : these symptoms only appear due to severe exercises
2- Stage 2 : these symptoms only appear due to moderate exercises
3- Stage 3 : these symptoms only appear due to light exercises
4- Stage 4 (which is the worst): these symptoms appear at rest
Cardiac cycle : one systole one diastole
,it lasts .8 seconds, and the
heart beats 75 beat/min
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Left ventricle
*The conditions of the left ventricle before systolic phase:
 The volume of the blood present At the end of diastolic phase in the left
ventricle is 120 ml.

the pressure in the left Atrium= 5mmHg, in the aorta= 80mmHg, In the
left ventricle= 0mmHg
*0mmHg equals atmospheric pressure (760) which is a reference point.
 Pressure in the atrium is higher than the pressure in the ventricle so the
AV valve is opened. but pressure in the ventricle is less than the pressure
in the aorta then the SL (semi lunar) valve is closed , so there is no
chance for ejection.
 Note: Opening and closing the valves depends on The pressure in the
champers
The Systolic phase
lasts .4 seconds (Atrial systole .1 sec+ ventricle systole .3
sec)
 The stimulus reaches the ventricles and the systolic phase starts, the contraction
of the atrium starts , and the pressure in the left ventricle begins to rise until it
reaches 6mmHg which is more than 5mmHg in the atrium so the AV valve
closes . but 6mmHg is less than 80mmHg
(Pressure in aorta) so the SL remains close.
 The ventricle now is a closed chamber .which means there is no filling or
emptying, so the volume of blood in the ventricle remains 120 ml .
o Isovolumic contraction phase : the ventricle contract but the volume
remains the same (120).-the first stage in systolic phase-
 The pressure rises rabidly in the ventricle, and when it reaches 81 mmHg the
aortic valve opens and the ejection starts.
o Rabid ejection phase - the second stage in systolic phase -
 During ejection there is more blood on aorta. this rises the pressure in the aorta
above 80mmHg, and the pressure in the ventricle keep exceeding the aortic
pressure to guarantee ejection .
o Note: to guarantee ejection, the intra ventricular pressure must exceed the intra
aortic pressure.

When the pressure in the ventricle reaches 120mmHg the systolic phase ends ,
and the ventricle start relaxing .
o Reduce ejection phase – the third and last stage in the systolic phase-

The ventricle has 120 ml (end diastolic volume) of blood. in the systolic phase
it ejects 70 ml ( stroke volume) and keeps 50 ml (end systolic volume) in each
contraction.
o SV= EDV – ESV
70 ml= 120 ml – 50 ml

Ejection fraction = (SV/EDV)% =(70/120)% = 60%
o Ejection fraction determines the integrity of the heart, if the fraction is less than 50%
that means a failure of the heart.
o A heart have stroke volume of 70ml and end diastolic volume of 120 ml is stronger
than a heart have the same stroke volume but 150ml end diastolic volume .
The diastolic phase (remains longer than systolic phase .4 seconds)
 The pressure in the ventricle starts to fall down under 120mmHg (*but still
above 5 mmHg), so all valves are closed.
o Isovolumic relaxation phase –first stage in diastolic phase
When the pressure becomes less than 5 mmHg and reaches 4mmHg, the AV
valve opens and the ventricle starts to fill with blood.
o Rabid filling phase –the second stage in diastolic phase-
 Reduce filling phase –the third stage in
Diastolic phase Atrial contraction phase –the last stage in diastolic phaseNote : these phases are involve in both sides of the heart , but here we are talking
about only the left side . left and right ventricles work by the same principles but
different values .
Heart sounds
 Opening valves don't make sounds
 Closing of the AV valve make the first sound , closing semi lunar valve make
the second sound
Summary _ left ventricle_
Excitation
Depolarization – QRS complex in ECG -
Contraction
Increasing of the pressure (0 to 6)mmHg
Closing AV valve
First heart sound
Systolic phase
Closing semi lunar valve
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done by: Mais Al-reem Al-housani
Heart sound 2