Materials Included In Kit

Additional Materials Required

Safety Precautions

Isopropyl alcohol is a flammable liquid and a moderate fire risk; slightly toxic by ingestion and inhalation. Wear eye protection and avoid sources of ignition when handling isopropyl alcohol. Check student records for any potential health problems. Remind students to wash hands thoroughly with soap and water before leaving the laboratory. Follow all normal laboratory guidelines. Please consult current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Isopropyl alcohol may be disposed of by evaporation according to Flinn Suggested Disposal Method #18a. Used cotton balls may be disposed of in the regular trash according to Flinn Biological Waste Disposal Method VI.

Lab Hints

• Enough materials are provided in this kit for 10 groups of students if the groups rotate the sphygmomanometer.
• This laboratory activity can reasonably be completed in one 50-minute class period. The laboratory should be read before coming to lab, and the data compilation and calculations can be completed after the lab.
• Add a “Partner 3” column to the data tables if students work in groups of three or have one student act as recorder, if needed.
• Suggest students wear short sleeve shirts on the day of the lab.
• If stools or steps are not available, substitute jogging, marching or jumping jacks to increase heart rate.

Answers to Prelab Questions

1. Calculate the average cardiac output for an adult woman.

   60 mL per beat x 76 bpm = 4560 mL per minute

2. Why is moderate aerobic exercise important for people who have had a heart attack?

   Aerobic exercise conditions the heart to deliver more blood volume per stroke of the heart. The lungs work more efficiently as well.

3. Calculate your target heart rate.

   Range: [(200 – age) x 60%] to [(220 – age) x 80%]
   For a 17-year-old (220 – 17) × 60% = 122
                              (200 – 17) x 80% = 162

Sample Data

Fitness Worksheet

Data will vary depending on students tested (e.g., their ages, genders). Remind students that the data obtained in this study are not for diagnostic purposes.

Answers to Questions

1. Calculate the total number of fitness points for each partner.

   This number should be the sum of the fitness points.

2. Compare the total number of fitness points to the values in the following table. Record the relative cardiac fitness of both partners. Note: The value is for experimental purposes only.
   {10820_Answers_Table_1}

   Based on the number of fitness points calculated in Question 1, this will be excellent, good, fair or poor.

3. Explain why heart rate increases during exercise.

   The heart must deliver greater quantities of oxygenated blood to the muscles.

4. Explain why high blood pressure is a health concern.

   High blood pressure causes greater force to be placed on the arteries and arterioles. The greater force can cause the blood vessels to rupture or otherwise damage the heart, liver, kidneys or brain.

Introduction

A circulatory system is composed of blood vessels, a pump, and fluid that allows for the delivery of oxygen and other nutrients and the removal of waste products. Mammals, including humans, have a closed circulatory system powered by contractions in a four-chambered heart. How does a closed circulatory system work? What factors affect the efficiency of the circulatory system?

Concepts

• Baroreceptor reflex
• Heart rate
• Blood pressure
• Pulmonary versus systemic circuit

Background

A closed circulatory system is one where blood never leaves the system of blood vessels and the heart. In animals with a four-chambered heart, the blood follows two distinct circuits as it passes through the body. The systemic circuit carries oxygenated blood from the left side of the heart, through the arteries and arterioles and finally to the capillaries, where the oxygen is delivered to the cells via diffusion. The deoxygenated blood then travels back through venules and the larger veins to the vena cava before being returned to the right atrium of the heart. In the pulmonary circuit, deoxygenated blood travels from the heart through the pulmonary arteries to the lungs, where oxygen diffuses into the blood. The blood then enters the pulmonary veins before returning to the heart. Note: Arteries carry blood away from the heart and veins carry blood to the heart, regardless of whether the blood is oxygenated or deoxygenated (see Figure 1).

The human heart goes through a very specific sequence or pattern of relaxing and contracting the cardiac muscle tissues—this pattern is called the cardiac cycle. One cardiac cycle equals one full sequence of contraction (emptying) and relaxation (filling) of the heart. The contraction phase of the cardiac cycle is called systole. The relaxation phase is called diastole.

Cardiac output is the measure of the volume of blood per minute pumped into the systemic circuit by the left ventricle. Cardiac output depends upon the heart rate (rate of contraction) and the stroke volume. The stroke volume is the amount of blood the left ventricle pumps with each contraction. At rest, the average stroke volume is approximately 70 mL per beat for a man and 60 mL per beat for a woman. At rest, the average heart rate for a man is 72 beats per minute (bpm) and 76 bpm for a woman. The average cardiac output for an adult man (at rest) is therefore 70 mL per beat x 72 bpm = 5040 mL of blood per minute. When this “average man” is not at rest, the body must deliver more oxygen to the tissues in order to maintain homeostasis. The cardiac output increases by increasing the heart rate since the stroke volume is nearly constant.

The body has a biofeedback system that increases or decreases the cardiac output based on the needs of the body tissues. Exercise, for example, causes the biofeedback system to increase the heart rate, increase the respiration rate and depth, increase the arterial pressure, decrease the blood flow to nonmuscular tissues, and increase the blood flow to the muscles. One way to determine the general or overall physical fitness of an individual is to measure how well the body responds to exercise. If an individual is physically fit, the body will be more efficient at delivering oxygen to the tissues, and the individual’s heart rate, respiration rate and arterial pressure will be lower than that of a similar, but unfit, person.

Blood Pressure

The entire circulatory system is under pressure, but the amount of pressure varies by location. Arteries have a higher pressure than veins, but within the same artery the blood pressure is greatest when the ventricles contract (systole). The point at which the arteries are under the highest pressure is called the systolic pressure. It is the systolic pressure that may be felt as a heartbeat or “pulse” in the carotid arteries of the neck or in the radial artery in the wrist. Blood pressure in the arteries depends on both the cardiac output and the resistance to blood flow through the slightly smaller arterioles called peripheral resistance. It is the additional pressure caused by the peripheral resistance that causes the artery to “bulge.” This bulge may be observed by resting an arm, thumb side up on a table and carefully observing the area adjacent to the median vein in the wrist for a pulse. The artery snaps back into shape during diastole and the pressure inside the artery is now at its lowest pressure, which is called the diastolic pressure.

Blood pressure may be measured using a device called a sphygmomanometer (pronounced sfĭg'mō-me-nŏm'ĭ-ter). A sphygmomanometer consists of an inflatable cuff connected by one rubber hose to a hand pump and by a second rubber hose to a pressure gauge. By convention, the pressure gauge is graduated in millimeters of mercury (mm Hg). The deflated cuff is wrapped around the upper arm (brachial artery) and inflated to a pressure above the systolic pressure. This restricts the blood flow through the artery. The artery is silent when there is no blood flowing past the inflated cuff (see Figure 2). The examiner places a stethoscope on the inside of the elbow, near the brachial artery, to listen for the sounds of blood flow. If the artery is silent, the examiner slowly opens the air valve to release the pressure on the cuff until some of the blood is pushed through the compressed walls of the artery in spurts. The blood flows in spurts because the pressure in the artery first rises above the pressure in the cuff and then drops back down, resulting in turbulence. The turbulence causes the artery to vibrate and also creates heart sounds called Korotkoff sounds. The sounds are named after Dr. Nikolai Korotkoff (1874–1920), a Russian physician who, in 1905, first described the heart’s sounds created using a pressure cuff. Dr. Korotkoff noted a “snapping” sound that occurs when the pressure in the cuff is just below the systolic pressure. At the first snapping sound, the pressure on the gauge is noted by the examiner. This is the systolic pressure and it is the first number repeated in a blood pressure reading. As the pressure in the cuff falls further, murmurs are audible. These sounds persist as long as the pressure in the cuff is between the systolic and diastolic pressures, as the arterial pressure keeps on rising above and then dropping back below the pressure in the cuff. The third sound is another loud thumping sound, although it is less clear than the initial thumping. The fourth sound appears within 10 mm Hg of the diastolic pressure. The sounds are muted thumps. The fifth “sound” is actually silence as the cuff pressure drops below the diastolic pressure. Prior to 2000, the last of the fourth sounds was used as the diastolic pressure. Since 2000 however, health professionals have been using the beginning of the fifth “sound,” silence, as the diastolic pressure. Blood pressure is commonly reported as a fraction, with the systolic pressure as the numerator and the diastolic pressure as the denominator (e.g., 120/80).

Blood pressure measurements depend on a person’s age, gender, heredity, and health. Blood pressure measurements that are chronically elevated may indicate a health problem. This condition is called hypertension and is a major risk factor for heart disease and stroke. Hypertension may be controlled using a combination of lifestyle changes and prescription drugs, as appropriate. The National Institutes of Health have determined that blood pressure readings for an adult that are consistently greater than 140/90 represent hypertension. Blood pressure readings of 120–139 systolic and 80–89 diastolic indicate prehypertension. Lifestyle changes are often sufficient to lower the blood pressure in someone suffering from prehypertension. Children and young adults have different “normal” ranges for both heart rate and blood pressure than adults. In general, heart rate drops as a person ages from an infant to an adult, whereas blood pressure increases. Table 1 provides typical blood pressure ranges and heart rates for both genders according to age. Note: This table is for experimental use only, and should not be used for diagnostic purposes. Heart Rate

In order for muscle tissue to receive more oxygen during physical exertion, the heart increases its contraction rate. A heart rate, also called the cardiac rate or pulse, is measured in beats per minute (bpm). The more times the heart contracts (beats) within one minute, the faster the heart rate. Many physiological factors or conditions influence heart rate—some of the most important include age, gender, heart disease, stress, thyroid problems, anemia, stimulants, depressants and other medications.

The maximum rate that a heart can beat is generally the same for people within the same age group. The maximum cardiac rate for an individual is calculated by subtracting the person’s age from 220. Individuals who are in good physical condition can deliver more oxygen to their muscles before reaching the maximum cardiac rate than can individuals in poor condition. People who are physically fit also pump a greater volume of blood with each contraction during physical exertion. As a result, a physically fit person’s heart does not need to beat as fast to deliver the same amount of oxygenated blood to the muscle tissues. An adult athlete in peak fitness may have a resting heart rate of 50–57 bpm, compared to a resting heart rate of 70–76 bpm for an average adult male. During physical exertion, a person who is in poor physical condition reaches the maximum cardiac rate at a lower work level than a person of comparable age who is in better shape. During physical exertion, the goal is not to reach the maximum cardiac rate but rather the target heart rate. The target heart rate is a range of heart rates that is calculated by multiplying the maximum cardiac rate by 60% and 80%—is considered the optimum value for each age group. This is the optimum level for achieving physical conditioning and strengthening of the circulatory system.

Physicians use several methods, including the resting heart rate and blood pressure, to determine how well the heart handles work. If a physician suspects a problem, other tests, such as the patient’s baroreceptor response, may be recommended. The baroreceptor response is determined by measuring the patient’s heart rate and blood pressure while reclining and then immediately after standing upright. The reclining heart rate is subtracted from the standing heart rate. The increase in the heart rate is initiated by baroreceptors (pressure receptors) in the carotid (neck) artery and in the aortic arch which detect a drop in blood pressure to the upper body upon standing. When these baroreceptors detect a drop in blood pressure in the upper half of the body they signal the medulla of the brain to increase the heart rate to increase the amount of blood flowing to the heart, lungs and brain. The baroreceptor response is a simple, noninvasive test that can be performed during an office visit.

Experiment Overview

The purpose of this experiment is to measure the blood pressure and heart rate under different conditions and to investigate how exercise and general fitness influence these measurements. There are four parts to this experiment. In Activity 1, a sphygmomanometer and stethoscope will be used to measure the blood pressure of each lab partner. In Activity 2, each lab partner’s resting heart rate will be measured. In Activity 3, the baroreceptor reflex of each lab partner will be calculated. In Activity 4, the endurance and relative cardiac fitness will be determined by measuring the response of the cardiovascular system to sudden changes in demand.

Materials

Prelab Questions

1. Calculate the average cardiac output for an adult woman.
2. Why is moderate aerobic exercise important for people who have had a heart attack?
3. Calculate your target heart rate.

Safety Precautions

Do not attempt this exercise if strenuous activity will aggravate a health problem. Isopropyl alcohol is a flammable liquid and a moderate fire risk. It is slightly toxic by ingestion and inhalation. Wear eye protection and avoid sources of ignition when using isopropyl alcohol. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Activity 1. Resting Blood Pressure

1. Work in pairs. One partner will act as the patient (partner 1) and the other as the examiner. The partners will then switch rolls and the examiner (partner 2) will become the patient. Note: Do not switch partner numbers during the laboratory—partner 1 should always be patient 1. All individuals should remain calm and quiet throughout the procedure while the blood pressure and heart rate are being measured.
2. Saturate two cotton balls with isopropyl alcohol. Use one cotton ball to clean the bell and diaphragm of the stethoscope (see Figure 3) and the second one to clean the earpieces of the stethoscope. Dispose of the cotton balls in the regular garbage.
   {10820_Procedure_Figure_3}
3. Partner 1 should be seated with his or her left shirtsleeve rolled up 5 inches above the elbow. However, make sure that the sleeve is not tight or binding. Place the left arm at heart level onto a desk or table, palm up.
4. The examiner should attach the cuff of the sphygmomanometer snugly around the upper arm of the patient, centering the bladder over the brachial artery (see Figure 4). The tubing should be aligned with the small finger and the lower edge of the cuff should be about one inch above the inner elbow. The examiner should be able to fit two fingers between the cuff and the arm.
   {10820_Procedure_Figure_4}
5. Place the bell of the stethoscope directly below the cuff in the bend of the elbow joint.
6. Close the valve of the bulb by turning it clockwise. Pump air into the cuff until the pressure gauge goes past 180 mm Hg. Caution: Do not inflate the cuff above 260 mm Hg.
7. Turn the valve of the bulb counterclockwise and slowly release the air from the cuff (about 2–3 mm Hg per second). Listen for the first “thumping” sounds while watching the gauge.
8. Note the pressure on the gauge when the first sounds are heard—this is the systolic pressure. Remember the pressure reading corresponding to the first sound.
9. Continue to slowly release air and listen carefully until the clear thumping sound of the pulse becomes strong and then fades. Note the pressure on the gauge when the silence begins. This is the diastolic pressure.
10. Record the systolic and diastolic pressures in the Activity 1 Data Table on the Fitness Worksheet.
11. Repeat the measurement two more times and record the systolic and diastolic pressures each time in the Activity 1 Data Table.
12. Calculate the average systolic and diastolic pressure for partner 1.
13. Switch roles and repeat steps 2–12, recording the systolic and diastolic pressures for partner 2.
14. Using the following data table as a guide, assign “fitness points” for both partner 1 and partner 2 based on their resting blood pressure. Record the values in the Activity 1 Data Table.
    {10820_Procedure_Table_2}

Activity 2. Resting Heart Rate

1. Saturate two cotton balls with isopropyl alcohol. Use one cotton ball to clean the bell and diaphragm of the stethoscope and the second one to clean the earpieces of the stethoscope. Dispose of the cotton balls in the regular garbage.
2. Determine the resting heart rate for partner 1.
   1. Partner 1 should remain quietly seated for two minutes before the resting heart rate is measured.
   2. Place the stethoscope over partner 1’s heart and count the number of beats for 20 seconds. Record the number of beats in the Activity 2 Data Table on the Fitness Worksheet.
   3. Determine partner 1’s resting heart rate (bpm) by multiplying the number of beats in 20 seconds by 3. Record the value in the Activity 2 Data Table.
3. Switch roles and repeat steps 1 and 2 for partner 2.
4. Assign “fitness points” for both partner 1 and partner 2 based on their resting heart rate. Record the value in the Activity 2 Data Table.
   {10820_Procedure_Table_3}

Activity 3. Baroreceptor Response

1. Determine partner 1’s reclining heart rate.
   1. Partner 1 should recline on the floor for two minutes. Note: Partner 1 should remain reclining throughout step 1 of this procedure.
   2. After two minutes, place the stethoscope over partner 1’s heart and count the number of beats for 20 seconds. Record the number of beats in the Activity 3 Data Table on the Fitness Worksheet.
   3. Determine partner 1’s reclining heart rate (bpm) by multiplying the number of beats in 20 seconds by three. Record the value in the Activity 3 Data Table.
   4. Using the data table below as a guide, assign fitness points based on the reclining heart rate of partner 1. Record the value in the Activity 3 Data Table.
   {10820_Procedure_Table_4}
2. Determine partner 1’s baroreceptor reflex.
   1. Partner 1 should stand up with arms at the side.
   2. Immediately determine partner 1’s standing heart rate: place the stethoscope over his or her heart and count the number of beats for 20 seconds. Record the number of beats in the Activity 3 Data Table on the Fitness Worksheet.
   3. Determine partner 1’s standing heart rate (bpm) by multiplying the number of beats in 20 seconds by three. Record the value in the Activity 3 Data Table.
   4. Determine partner 1’s baroreceptor reflex by subtracting the reclining heart rate from the standing heart rate. Record the value in the Activity 3 Data Table.
3. Using the following data table as a guide, assign fitness points based on the heart rate increase for partner 1. Record the value in the Activity 4 Data Table.
   {10820_Procedure_Table_5}
4. Switch roles and repeat steps 1–3, recording the heart rates and fitness points for partner 2.

Activity 4. Endurance

1. Saturate two cotton balls with isopropyl alcohol. Use one cotton ball to clean the bell and diaphragm of the stethoscope and the second one to clean the earpieces of the stethoscope. Dispose of the cotton balls in the regular garbage.
2. Determine partner 1’s endurance.
   1. Partner 1 will simulate climbing a short flight of stairs.
      1. Partner 1 should place his or her right foot on an 18-inch high stool.
      2. Raise his or her body so that the left foot comes to rest by the right foot.
      3. Place the right foot on the floor. Place the left foot on the floor next to the right foot.
      4. Repeat the exercise for two minutes, allowing three seconds for each step cycle.
   2. Record the time when partner 1 stops “stepping” on the Activity 4 Data Table.
   3. Immediately count the number of heartbeats for 15 seconds. Record the number of beats on the Activity 4 Data Table.
   4. Determine partner 1’s endurance heart rate (bpm) by multiplying the number of beats in 15 seconds by 4. Record the value in the Activity 4 Data Table.
   5. Continue monitoring partner 1’s heart rate, recording the time at which partner 1’s heart rate returns to the resting heart rate determined in Activity 2.
   6. Subtract the times to determine the length of time (in seconds) it took for partner 1’s heart hate to return to the resting heart rate. Record the amount of time in the Activity 4 Data Table.
3. Determine the heart rate response.
   1. Subtract partner 1’s resting heart rate from the heart rate immediately after completing the simulated stair climbing exercise (the 0 to 15 second interval). Record the value in the Activity 4 table of the Fitness Worksheet.
   2. Using the following data table as a guide, assign fitness points based on the number of beats the heart rate increased (step 2d). Record the value in the Activity 4 Data Table.
   {10820_Procedure_Table_6}
4. Using the following data table as a guide, assign fitness points based on the number of seconds it took for the heart rate to return to the resting heart rate. Record the value in the Activity 4 Data Table.
   {10820_Procedure_Table_7}
5. Switch roles and repeat steps 1–4, recording the heart rate and fitness points for partner 2.
6. Answer the questions on the Fitness Worksheet.

Student Worksheet PDF

10820_Student.pdf