Cardiac Cycle

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Cardiac Cycle Ventricular systole -
isovolumic contraction - ejection
Ventricular diastole - isovolumic
relaxation - rapid filling - atrial
contraction
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• Isovolumic
• Ventricular Contraction

2) Ventricular Ejection
3) Isovolumic Ventricular Relaxation
4) Ventricular Filling
5) Atrial Contraction
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Conclusion ?
The heart generates electricity.
Motor nerve
Skeletal muscle
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TERMINOLOGY Excitation - definition
generation of action potentials - different
from contraction Contraction - definition
shortening of muscle cells - triggered by
excitation
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Properties of Cardiac Muscle
Excitation of the heart is triggered by
electrical impulse rather than neural
transmitters. Contraction of the heart is
triggered by elevation of intracellular calcium
influx.
Ca i
Contraction
Excitation
(Action Potentials)
(shortening)
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RRole of a Long Refractory Period 1 prevent
ventricles from contracting at too high rates so
that enough time is allowed for refill of the
ventricles
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EELECTROCARDIOGRAPHY ((ECG) the recording of
electrical activities of the heart via electrodes
placed on body surface.
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Bradycardia slow heart rate ( lt 60
beats/min)   Tachycardia fast heart rate ( gt
100 beats/min)
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Artificial Pacemaker Application sinus
abnormality, complete AV or ventricular
block Function - generate electric pulses -
sensing - antitachyarrhythmia
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MECHANICAL PROPERTIES OF THE HEART
CONTENT Heart Rate Stroke volume Cardiac Output
(CO) Ejection Fraction Preload Afterload Contracti
lity Frank-Starling Mechanism Factors on Cardiac
Output
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Heart Rate the number of heart beats in 1
minute. Normal value 60-100/min Stroke
volume the volume of blood pumped out by each
ventricle per each contraction.

SV
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Cardiac Output (CO) the amount of blood pumped
out by each ventricle in 1 minute. Cardiac
output stroke volume x heart rate Example
70 ml x 75 beat/min 5,250 ml/min
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Ejection Fraction stroke volume ?end-diastolic
ventricular volume
70 ml ? 130 ml 54
60 ml
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Ejection Fraction
SV
120 ml
133 ml
End of diastole
End of systole
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2) Chemoreceptor Reflex
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Blood Supply to Cardiac Muscles
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Coronary Atherosclerosis
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Ccomposed of lipid, smooth muscle, macrophages,
and connective tissues. cause stenosis of
coronary arteries
Histology of the plaque
 occlude arterial lumen when combined with
internal hemorrhage, thrombosis, and arterial
spasm
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Surgical Therapies
1)
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