(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
• T-R interval
– Duration of ventricular
ECG Exercises
– 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)
Cardiac Cycle
• contraction (systole) +
relaxation (diastole) of
• lasts 0.8 sec (based on 72
• Listen for the heart
sounds w/ stethoscope
• Best heard in different
Cardiac Cycle - Heart Sounds
• “lub” = closing of the
AV valves
• “dub” = closing of the
semilunar valves
Arterial Blood Pressure
• Pressure blood exerts on arterial
• 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
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
– 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.
Fitness Activity
Measure reclining and standing HRs
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!