(ECG) Electrocardiogram (ECG)

Path of Cardiac Excitation
• Sinoatrial (SA) Node
Cardiovascular Physiology
– pacemaker of the heart
• Atrioventricular (AV) Node
– Delays conduction to ventricles
• Bundle of His
Lab #10
– conducts signal through
interventricular septum
• Purkinje fibers
– conduct signal up lateral walls
of ventricle
Path of Cardiac Excitation
• SA node cells produce APs
• Atrial fibers activated
Electrocardiogram (ECG)
• P wave
– depolarization of atria just
before contraction
– atrial contraction
• APs excite AV node
• QRS wave
– delay (complete atrial contract)
– depolar. of ventricles just
before contraction
– also atrial repolarization
• APs of AV node travel down
AV bundle to apex of heart
• signal conducted to Purkinje
fibers throughout ventricles
• Myocardial fibers activated
• T wave
– repolarization of the ventricles
– ventricular contraction
Electrocardiogram (ECG)
• Record ECGs before and after exercise
• Measurements
• P-R interval
– Atrioventricular delay
• R-T interval
– Duration of ventricular
systole
• T-R interval
– Duration of ventricular
diastole
ECG Exercises
P-R
R-T
T-R
– Duration of a cardiac cycle (T-T)
– Measurement of heart rate
– Measurement of atrial systole and the A-V
delay (P-R)
– Measurement of ventricular systole (R-T)
– Measurement of ventricular diastole (T-R)
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Cardiac Cycle
• contraction (systole) +
relaxation (diastole) of
ventricles
• lasts 0.8 sec (based on 72
beats/min)
Auscultation
• Listen for the heart
sounds w/ stethoscope
• Best heard in different
positions
Cardiac Cycle - Heart Sounds
• “lub” = closing of the
AV valves
• “dub” = closing of the
semilunar valves
Arterial Blood Pressure
• Pressure blood exerts on arterial
walls
• Systolic blood pressure
– pressure of blood in arteries during
ventricular systole
• Diastolic blood pressure
– pressure of blood in arteries during
ventricular diastole
• Indicates blood flow to the body
and work load of the heart
Measure Blood Pressure
Cardiovascular Fitness
• Regular exercise
• Sphygmomanometer
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Apply cuff
Apply pressure to ~180 mmHg
Release pressure slowly
Auscultate brachial artery for
sounds of Korotkoff
– Increased stroke volume
– Greater cardiac output
• Can maintain exercise longer
– Less increase in HR needed to meet blood flow
demands
– Activity of heart muscle itself is lower
• Can recover from exercise more quickly
• Can compensate for changes in blood flow due to
positional changes more effectively.
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Fitness Activity
1.
Measure reclining and standing HRs
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2.
3.
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4.
determine change in pulse rate and score
Calculate change in systolic BP as you go from a
reclining position to a standing position
Perform exercise on stool, (3 seconds each cycle, 5x)
record HR (15 sec x4)
measure pulse at 30, 60, 90 and 120 sec after completion (15 sec
x 4)
record time for pulse to return to normal standing rate.
subtract normal HR from exercise HR
Tally up scores and see how fit you really are!
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