Download The Cardiac Cycle Cardiac conduction system Cardiac Muscle

The Cardiac Cycle
Bio 250 Laboratory Exercise
Cardiac conduction system
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This system,
composed of
specialized cardiac
muscle tissue, initiates
and conducts
depolarization waves
though the
myocardium.
Impulses from the S-A
node pass slowly to
the A-V node;
impulses travel rapidly
along the A-V bundle
and Purkinje fibers.
Cardiac Muscle (Myocardium)
„
Muscle fibers
in the
ventricular
walls are
arranged in
whorls that
squeeze blood
out of the
contracting
ventricles.
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Some Terminology
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Systole- contraction and pumping phase
of the cardiac cycle
Diastole- relaxation and filling phase of
the cardiac cycle
Atrial and ventricular systole alternate
with each other
The electrocardiogram
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P-wave occurs as the atria depolarize
QRS-complex occurs as the ventricles
depolarize
T-wave occurs as the ventricles repolarize
P-R Interval extends from beginning of Pwave to the beginning of the QRS-complex
Q-T Interval extends from the end of the PR Interval to the end of the T-wave
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ECGs, Normal & Abnormal
No P waves
ECGs, Abnormal
Arrhythmia: conduction failure at AV node
No pumping action occurs
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Physiograph
Physiograph will measure:
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Electrocardiogram- electrical activity of
the heart and its conduction system
Heart Sounds- sounds made as the AV
and SL valves close
Pulse Pressure- rising pressure during
ventricular systole and falling pressure
during ventricular diastole
Dicrotic notch- blood rebounding off SL
valves as they close
ECG
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Einthoven’s Triangle
Standard Leads
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I
II
III
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Heart Sounds Microphone
Plethysmograph
Subject wired to ECG, heart
microphone and plethysmograph
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Cardiac Cycle
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Things to Remember
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Plethysmogram- pressure rises during
systole (contraction) of the ventricle
and falls during diastole (relaxation).
Electrocardiogram„
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P wave represents the action potential that
passes over the atria and causes atrial
systole.
QRS complex wave represents the action
potential that passes over the ventricles
and causes ventricular systole.
Continued
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Heart Sounds
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The first heart sound occurs when the AV
valves (tricuspid and mitral) close at the
beginning of ventricular systole
The second heart sound occurs when the
SL valves (aortic and pulmonic) close at
the end of ventricular systole
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