Cardio Exercise
1. Explain blood flow through the heart, naming the major blood vessels entering and exiting the heart, the chambers, and valves.
*2. Compare the anatomy of the walls of arteries and veins and relate this to function.
3. Describe the systemic and pulmonary blood circulation routes.
*4. Explain how the conduction system of the heart functions and what factors may affect its rate.
5. Describe what occurs in the 0.8 second of a cardiac cycle.
CIRCULATORY LAB SUPPLEMENT
One of the frequently used tests in cardiac physiology, is the determination of the cardiac output. The cardiac output(CO) is the amount of blood leaving the heart in one minute. It is determined mathematically by multiplying the stroke volume(SV) by the heart rate(HR) or pulse. The formula can be written as follows: CO = SV X HR.
In order to determine the cardiac output, one needs to know the stroke volume. It is the amount of blood pumped per beat by the heart. Its usually has a value of around 70 - 80 cc.
The other thing you need to know is the heart rate or pulse. It is taken by measuring the pulse at the apex of the heart, the common carotid artery in the neck, or at the radial artery in the wrist. Its value is usually around 75, that is, 75 beats per minute. But it can range from about 60 to 150.
If a person has a SV of 76 cc, and a pulse of 92, her cardiac output will be 76 times 92, or 6992 cc per minute. To make this a more manageable number, it should be converted to liters by dividing the answer by 1000, or moving the decimal point 3 places to the left. Thus, the correct answer would be 6.99 liters/minute.
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If you know 2 of the 3 values in the above formula, you should be able to determine the other. For example, the cardiac output may be 7.6 liters per minute and the heart rate might be 98. From this you can figure out the stroke volume as follows. CO = SV X HR
SV X HR = CO
SV = CO
HR
Thus, by transposing the equation, you simply substitute the known values into your new formula.
CO = 7.6 liters(L) or 7600 ml
SV = 7600
98
SV = 77.6 ml
Similarly, you can determine the heart rate if you know the other 2 values. If a person has a cardiac output of 4.8 liters/minute and a stroke volume of 100 cc, what is her heart rate?
CO = SV X HR
SV X HR = CO
HR = CO
SV
Again, by transposing the equation, you substitute the known values into your new formula, as follows.
HR = 4800
100
HR = 48
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If you know a person's blood pressure and pulse, you can determine her pulse pressure, stroke volume and cardiac output.
The pulse pressure is the mathematical difference between the systolic and diastolic blood pressure readings. For example, if a person has a blood pressure of 140/78, and a pulse rate of 80, her pulse pressure would be 140 minus 78, or 62. This is measured in millimeters of Mercury, and is abbreviated mmHg. Thus, her pulse pressure would be 62 mmHg.
The stroke volume is determined by taking the pulse pressure and multiplying by a constant(K). The constant used is 1.7; thus, the pulse pressure in our example would be determined by multiplying 62 by 1.7. The answer is 105.4; the unit of measure is milliliters/beat or just milliliters(ml). Remember, that a milliliter is the same as a cubic centimeter, or cc.
The cardiac output is the stroke volume times the pulse rate, or heart rate. Note that the pulse is not the same as the pulse pressure. It is an indirect measure of the heart rate. In the sample above, the formula for cardiac output would be:
CO = SV X HR
Thus, multiplying the stroke volume(105.4) times the pulse(80) gives a value of 8432 ml/minute. When this is divided by 1000, the value is recorded as 8.4 liters/min or 8.4 L/min.
If the same individual has a cardiac output of 16.4 liters/minute after running up 3 flights of stairs, you can also figure her percent increase in cardiac output. The formula is:
% increase = CO after exercise minus CO before exercise
CO before exercise
Thus, the percent increase would be 16.4 minus 8.4, or 8.0. This number is then divided by 8.4; the new value is 0.95 Since this is a decimal, you have to multiply by 100 to convert to percent. .95 times 100 equals 95%. Thus, by running up 3 flights of stairs, our "athlete" had a 95 percent increase in cardiac output.
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The heart rate can be determined from the electrocardiograph recording(EKG) by measuring the distance in millimeters(mm) between two successive QRS complexes. The highest point of the QRS is the R wave. Using standard paper speed of 25 mm/second, the heart rate can be determined. The formula is:
HR = 1500
number of mm between 2 successive R waves.
If the length between R waves is 25 mm, then the calculation would be:
HR = 1500
25
HR = 60
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1. Closing of the tricuspid and bicuspid valves produce the ? sound, and closing of the aortic and pulmonary valves produce the ?-- sound of the heart.
2. In order to eject blood from the left side of the heart the pressure in the ? ventricle must be greater than the pressure in the aorta; similarly, the pressure in the right ventricle must be greater than in the ?--
3. The ? artery can be palpated at the wrist.
4. The ? artery can be palpated in front of the ear.
5. The ? artery can be palpated on the dorsal part of the foot.
6. Low ? can reduce the pulsations in the aorta and its branches causing the radial pulse to be weaker and harder to feel.
7. When changing from a horizontal position(i.e., lying down) to a standing position, your blood pressure will initially ?--.
8. The pulsations of the wall of the aorta and its branches are due to the ejection of blood from the ? during systole.
9. The alternate series of extension and recoil of the walls of arteries during systole is called the ?--.
10. Blood pressure determinations are really "arterial" blood pressures because most of the `pressure' has been used up in the ?-- , due to the great resistance that blood meets as it passes through these vessels.
11. The actual depolarization of the right atrium produces the ? wave.
12. The actual depolarization of the ventricles produces the ? wave.
13. Because the right ventricle is smaller and thinner-walled than the left, it ? before the left ventricle.
14. Repolarization of the atria is masked over by the ? wave.
15. Repolarization of the ventricles produces the ? wave.
16. The PR interval is the time between the beginning of the ? wave and the beginning of the ? wave.
17. What muscular event occurs immediately after the P wave?
18. What muscular event occurs immediately after the QRS wave?
19. Blood pressure in the heart is the highest during the ? stage, or period of ejection of blood.
20. During strenuous exercise, the cardiac output changes significantly. What is the advantage of a large increase in cardiac output?
21. The immediate stimuli that results in an increased blood flow to active skeletal muscles is the buildup of ? and the decrease in ?-- from muscle cells.
22. The "all or none law" of the heart implies that a nerve impulse will spread to all muscle fibers because of the ? nature of cardiac muscle fibers.
23. A heart rate over 170 is ineffective to increase cardiac output because the time of ventricular ? is reduced considerably; thus, each additional stroke volume is reduced rather than increased.
24. When we say the heart is "well conditioned" we mean that the ? to the heart muscle is adequate or above the normal.
25. You may sometimes observe a slight difference between the values obtained from an apical pulse and an arterial pulse taken elsewhere on the body. What is this difference called?
26. What is the name of the instrument used to compress the artery and record pressures in the auscultatory method of determining blood pressure?
27. What are the sounds of Korotkoff?
28. Interpret 145/85/82.
29. Trace the path of a molecule of oxygen from the alveolus of the lung to the right atrium of the heart. Name all structures through which it passes.
30. Most arteries of the adult body carry oxygen-rich blood, and the veins carry oxygen-depleted, carbon dioxide-rich blood. What is different about the pulmonary arteries and veins?
ANSWERS
1. lubb;dup
2. left; pulmonary trunk
3. radial
4. temporal
5. dorsal pedal
6. stroke volume
7. decrease
8. left ventricle
9. pulse
10. arterioles
11. P
12. QRS
13. depolarizes
14. QRS
15. T
16. P;Q
17. atrial contraction
18. ventricular contraction
19. 3rd
20. more blood with oxygen to contracting muscles.
21. CO2; O2
22. branching
23. systole
24. coronary circulation
25. pulse deficit
26. sphygmomanometer
27. pulsations at elbow when taking blood pressure
28. systolic BP=145; diastolic BP=85; pulse = 82
29. work out on your own
30. pulmonary artery carries dexoygenated blood; pulmonary vein carries oxygenated blood
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SAMPLE MATHEMATICAL PROBLEMS IN CIRCULATION
DIRECTIONS: Figure out the following problems. Then check your answers against the KEY on the back page.
Maryland nursing and allied health students are having their annual health screening test for members of the national media. These folks heard of the great prowess of Marylands Nursing and Allied Health departments. Some of their test data is included so you can see what kind of physical fitness they possess.
1. Dave Letterman has his blood pressure taken by a MD nursing student. It is found to be 119/80. His pulse was 66. What is Dave's pulse pressure?
2. What is Dave's stroke volume?
3. What is Daves cardiac output?
4. Tom Brokaw was the next to get his blood pressure checked. Tom's blood pressure was 135/78. His pulse was 88. What was his stroke volume?
5. What was Tom's cardiac output?
6. Roseanna Barr stopped by also. Her blood pressure was 105/66 and her cardiac output was 5.3 liters per minute. What was her stroke volume?
7. Bill Cosby had his blood pressure determined. Later he found that he had a stroke volume of 79.5 ml and a cardiac output of 6.2 liters. What was his heart rate?
8. Mark Russell took advantage of the EKG screening. He wanted to know what his pulse rate was based on his EKG. There were 25 mm between the peaks of 2 successive QRS complexes. What was his pulse rate?
9. In Marks EKG, the PR interval was measured at 3 mm. What was the PR interval?
10. George Michael from Channel 4 had a heart rate of 90. What was the length of one cardiac cycle?
11. Barbara WaWa's heart beat lasted 0.47 seconds. What was her heart rate?
12. Bryant Gumbel's heart rate was 60. What was the length of one of his cardiac cycles?
13. Willard Scott, in one of his lazier moments, found that the duration of his heart beat was only 0.9 seconds. What was Willard's pulse rate?
14. The American Idol has a blood pressure of 125/86 and a pulse rate of 99.
A. What is her pulse pressure?
B. What is her stroke volume?
C. What is her cardiac output?
15. Bob Ryan has a cardiac output of 7.56 liters per minute. His pulse rate is 77. What is his stroke volume?
16. If an individual has 26 mm between successive P waves on the ECG, and the chart speed is 25 mm per second, what is her atrial rate of contraction?
17. If an individual has 21 mm between successive QRS waves on the ECG, the chart speed is 25 mm per second, what is her ventricular rate of contraction?
18. If an individual has 4 mm in the PR segment, what is the duration of this period?
19. If an individual has a `length' of 11 mm on lead I, and a length of 15 mm on lead II of an electrocardiograph tracing, what is her mean electrical axis? Note: use your EKG exercise to figure out your answer.
Answers to circulatory problems
1. 39 mmHg
2. 66.3 ml/beat
3. 4.38 liters/minute
4. 96.9 ml/beat
5. 8.53 liters/minute
6. 66.3 ml/beat
7. 78
8. 60
9. 0.12 seconds
10. 0.67 seconds
11. 128
12. 1.0 seconds
13. 67
14A. 39 mmHg
14B. 66.3 ml
14C. 6.56 liters/minute
15. 98.2 ml
16. 58
17. 71
18. 0.16 seconds
19. +45
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