Blood Pressure and Heart Rate
Each time the ventricles contract, about 70 mL of blood is forced into the arteries. Every time this happens, the pressure is raised throughout the arterial system. This arterial pressure, however, falls as the blood is pushed through the capillaries. Then a new ventricular contraction repressurizes the system. This rhythmic change in arterial pressure is called the pulse and can be felt almost anywhere an artery can be pressed by a finger.
If you exercise vigorously, the rate of your heartbeat, that is, your pulse rate, increases. The amount that it increases depends on how fit you are. A strong heart can pump blood more efficiently than a weak one, therefore, the pulse rate of a physically fit person will not increase as much with exercise as will that of a physically unfit person. One measure of fitness is the Heart Performance Score (HPS).
Blood pressure and heart rate can be affected by the activity the body is performing. In this activity, you will investigate the effect of posture and exercise on heart rate and blood pressure.
For all steps, record all data in a table format. Also, collect data for each step for each partner.
Part A - Pulse
Note: For all pulse rate measurements, take the radial pulse for 20 s; then multiply by 3 to get the pulse rate in beats per minute. Resting heart rate can be used as an indicator of cardiovascular fitness. The best time to take resting heart rate is while sitting quietly after a period of inactivity.
1. Make sure you can find the radial pulse in both wrists and in those of your partner.
2. Have your partner use one hand to find the radial pulse and, at the same time, use the other hand to find the carotid pulse. Concentrate carefully, do they occur at the same time?
3. Using a stethoscope, determine whether the pulse corresponds to the first or second heart sound.
Part B - Blood Pressure and Heart rate
4. Measure your blood pressure while sitting quietly.
5. To improve the accuracy of our data, the exercise you should do is running on the spot for the prescribed time. To see any meaningful results, it is very important that you measure heart rate exactly when you are supposed to. Make sure that you and your partner are organized so that you can get the results quickly. Measure and record your heart rate for each of the following conditions:
(i) lying (ii) standing (iii) after 60 s of exercise (iv) after 60 s of rest after exercise
6. Add your data to the class pool so that averages for the class can be calculated.
Part C - Heart Performance Score
7. Calculate your HPS by adding together the 4 pulse rates (lying down, standing, after 60 s of exercise, after 60 s of rest after exercise) plus the difference between your sitting and standing heart rate.
8. Check the chart to see your general fitness level.
Part D - Breathing Rate
9. Sit very still. Count only the number of times you inhale for one minute. Pool your data with the class. Find the average.
9. Run on the spot for 60 s and then count the number of inhalations for one minute. Pool the data with the class and calculate the average.
Part E - Air Inhalation Time
When you inhale, air rushes into the lungs to fill an expanding chest volume. Determine your inhalation time by trying this short investigation.
10. Exhale until you can force no more air out of your lungs.
11. Have your partner measure the time taken for a full inhalation through just your nose. This is not a race so don’t try to force the air - just breathe normally.
12. Repeat the previous two steps, this time inhaling by mouth only.
Part F - Bradycardia - Slowing the Heart Rate
13. Begin by having the subject practice inhaling moderately and holding his/her breath for 35 s. The recorder should time this breath-holding and then the subject and recorder should reverse roles to permit the subject to rest for a minute or so between each breath-holding.
14. After two or three practice trials, the subject should have his/her partner take the heart rate by taking the radial artery pulse during the last 15 s of the 35 s of breath-holding. Record the heart rate for 15 s.
15. Repeat this activity three times. Average the three heart rates and then calculate the heart rate per minute.
16. Evaluate your data by comparing the heart rate found here to the one in Part B. If bradycardia has occurred, your heart rate should have decreased noticeably.
1. a) Which occurs first, the radial or carotid pulse? (carotid)
b) Which pulse is located closer to the heart? (carotid)
c) Explain why the carotid and radial pulses are not in time with each other? (pulse of blood must travelfurther to the wrist than the neck so more time is required)
2. a) What causes the pulse? (expansion of the artery as blood enters)
b) Why can the pulse rate be used to measure the heart rate? (because pulse is caused by heart pumpingblood)
3. What is the average breathing rate before and after the exercise? Explain any difference. Account for any difference between your results and the class average.
4. a) Account for the difference between mouth and nose inhalation times. (diameter of nostrils assmaller than mouth so air cannot be taken in as quickly; hair in nostrils also provides resistance.)
b) How does the size of the air passage affect the breathing rate? (larger passage means faster breathingpossible)
c) What advantages does mouth breathing have? (faster)
d) What advantages does nose breathing have? (detect odors which may be harmful; filter particles)
5. Calculate the average HPS for the whole class, the average for males and the average for females. Compare your HPS to the class and to the average for your sex. Account for any difference.
6. a) What is the immediate effect of exercise on the heart? (increases the heart rate)
b) Explain what causes the heart to react in this way. (increased carbon dioxide in the blood)
c) How does the body benefit from the change in heartbeat rate when the body is being exercised? (increased blood supply to all cells; increases oxygen and nutrient supply and removal of wastes)
d) Why does the heart itself need more oxygen during exercise? (working harder so needs more oxygen)
e) Describe the effect of resting after exercise on the heartbeat rate. (heart rate gradually decreases toresting)7. a) Each ventricle pumps out 70 mL of blood with every beat. How many beats are necessary to pump4.2 L of blood through the heart? (60 beats)b) How long would this take at your resting heartbeat rate?c) How long would this take when your body is hard at exercise?
7. a) Research the topic of bradycardia (or brachycardia) as it relates to the diving response in mammals.
b) What are the advantages in reducing the heart rate while under water?
c) Describe other physiological adaptations related to bradycardia.
d) When is bradycardia useful to humans?
e) When can bradycardia be a problem for humans?