Download 7 - ISpatula

Cardiovascular system- L3
Faisal I. Mohammed, MD, PhD
Yanal A. Shafagoj MD, PhD
University of Jordan
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Electrical Activity
of the Heart
Different Expression levels and
Different types of ion channels
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Electrocardiogram
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ECG or EKG
Composite record of
action potentials
produced by all the
heart muscle fibers
Compare tracings
from different leads
with one another and
with normal records
3 recognizable waves
 P, QRS, and T
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The Electrocardiogram
The major deflections and intervals
in a normal ECG include:
 P wave - atrial depolarization
 P-Q interval - time it takes for
the atrial kick to fill the
ventricles
 QRS wave - ventricular depolarization
and atrial repolarization
 S-T segment - time it takes to empty the ventricles
before they repolarize (the T wave)
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Correlation of ECG Waves and Systole
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Systole means ventricular contraction and diastole means
ventricular relaxation. Cardiac cycle events are:
Cardiac action potential arises in the SA node → P wave
Atrial systole (Atrial contraction)
Action potential enters AV bundle and leaves to the
ventricles → QRS complex which masks atrial
repolarization (un-recordable)
Contraction of ventricles (systole)
 Begins shortly after QRS complex appears and
continues during S-T segment
Repolarization of ventricular fibers → T wave
Ventricular relaxation/ diastole
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Cardiac Cycle
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All events associated with one heartbeat
Systole and diastole of atria and ventricles
In each cycle, atria and ventricles alternately contract and relax
 During atrial systole, ventricles are relaxed
 During ventricle systole, atria are relaxed
Forces blood from higher pressure to lower pressure
During relaxation period, both atria and ventricles are relaxed
 The faster the heart beats, the shorter the relaxation period
 Systole and diastole lengths shorten slightly
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Cardiac Cycle
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Cardiac cycle refers to all events associated with
blood flow through the heart
 Systole – contraction of heart ventricles
 Diastole – relaxation of heartventricles
Cardiac Cycle
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Ventricular systole 0.3 second
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Ventricular diastole 0.5 seconds
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Isovolumic contraction phase
Rapid ejection period
Slow ejection period
Isovolumic contraction phase
Rapid filling phase
Slow filling (Diastasis)
Atrial contraction phase
Phases of the Cardiac Cycle
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R
T
P
(a) ECG
1
4
8
Q
Atrial depolarization
2
Begin atrial systole
3
End (ventricular) diastolic volume
4
Ventricular depolarization
5
Isovolumetric contraction
6
Begin ventricular ejection
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End (ventricular) systolic volume
8
Begin ventricular repolarization
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Isovolumetric relaxation
S
0.1
sec
Atrial
systole
0.3 sec
Ventricular
systole
120
0.4 sec
Relaxation
period
9
Dicrotic wave
100
Aortic
pressure
5
80
6
(b) Pressure
(mmHg)
1
Left
ventricular
pressure
60
40
Left atrial
pressure
10
20
2
0
(c) Heart sounds
S1
S2
S3
S4
3 End (ventricular) diastolic volume
130
10 Ventricular filling
Stroke
volume
(d) Volume in
ventricle (mL)
60
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0
(e) Phases of the
cardiac cycle
Atrial
contraction
Isovolumetric
contraction
UniversityIsovolumetric
of Jordan
Ventricular
ejection
relaxation
Ventricular
filling
Atrial
contraction
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Stroke Volume
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SV = end diastolic volume (EDV) minus end systolic
volume (ESV)
EDV = amount of blood collected in a ventricle at the
end of diastolic phase
ESV = amount of blood remaining in a ventricle after
contraction
Cardiac cycle …cont
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End diastolic volume (EDV) – End systolic
volume (ESV) = Stroke volume (SV)
SV X heart rate (HR) = cardiac output (CO)
Ejection fraction = SV/EDV
Autonomic control of cardiac cycle (pump)
The EDV equals 110-120 ml and SV equals
70 ml. Therefore the ejection fraction is 65%
Cardiac Output
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CO = volume of blood ejected from left (or right)
ventricle into aorta (or pulmonary trunk) each minute
CO = stroke volume (SV) x heart rate (HR)
In typical resting male
 5.25L/min = 70mL/beat x 75 beats/min
Entire blood volume flows through pulmonary and
systemic circuits each minute
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Thank You
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