Lab 10   Physiology of the Circulatory System

Introduction: The human circulatory system is a collection of structures thorough which oxygen and nutrient rich blood flows to all tissues of the body for metabolism and growth, and to remove metabolic wastes. The blood is pumped to these tissues by the heart through a circuit composed of arteries, arterioles, capillaries, venules, and veins. Oxygenated blood is pumped to the tissues from the left side of the heart, whereas deoxygenated blood is pumped to the lungs from the right side of the heart. This circuit where gas exchange takes place within the alveoli of the lung is very important and is known as the pulmonary circuit. When the body is exercised changes can take place in the circulatory system that allow more blood to pass to actively respiring muscle cells and less to nonmuscular tissue. Increased heart rate, arterial pressure, body temperature, and breathing rate also occur during exercise.

Arterial blood pressure is directly dependant on the amount of blood pumped by the heart per minute and the resistance to blood flow through the arterioles. This is an important measurable aspect of the circulatory system and it is measured using a sphygmomanometer. This device has an inflatable cuff that connects to a hand pump and a pressure gauge, graduated in millimeters of mercury, by rubber tubing. The cuff is wrapped around the upper arm and inflated, the person taking the pressure then listens for two sounds and observes the gauge to determine what the blood pressure is. The systolic number is determined by the first noise heard as the cuff is deflated, and the diastolic number is determined by the last distinct noise heard.

Hypothesis: From this experiment it is expected that a subjectís heart rate and blood pressure will change during rest and exercise based on how physically fit they are. If the subject is in good shape the heart rate will not increase significantly and the blood pressure will increase. The opposite is true of someone in poor shape.

Materials: The materials used in this experiment include a blood pressure kit, alcohol swabs, a stopwatch, two depression slides, a cotton ball, four rubber bands, a pipet, a petri dish, a Daphnia culture, a stereomicroscope, and some ice.

Methods:

A. Measuring Blood Pressure: To measure blood pressure, one member of the lab group sat down in a chair, rolled up his sleeve, and then the sphygmomanometer cuff was placed around his upper left arm at heart level. The cuff was then pumped to 200mm Hg, which is safely higher than the blood pressure of the subject. The stethoscope was then placed in the well of the subjectís elbow, where the brachial artery is located, and pressure was slowly released as the taker listened for a pulse. The pressure on the gauge was noted when first sound of Korotkoff was heard, which is the pressure that blood is first able to pass through the artery during systole, representing systolic pressure. The sounds of Korotkoff are heard between the systolic and diastolic blood pressures. The diastolic pressure is the reading of the gauge at the time the sounds of Korotkoff can no longer be heard. The subjectís blood pressure was taken two more times and an average was calculated and recorded in Table 1.

Average Blood Pressure

 

Systolic Pressure

Diastolic Pressure

Age in Years

Men

Women

Men

Women

10

103

103

69

70

11

104

104

70

71

12

106

106

71

72

13

108

108

72

73

14

110

110

73

74

15

112

112

75

76

16

118

116

73

72

17

121

116

74

72

18

120

116

74

72

19

122

115

75

71

20-24

123

116

76

72

25-29

125

117

78

74

30-34

126

120

79

75

35-39

127

124

80

78

40-44

129

127

81

80

45-49

130

131

82

82

50-54

135

137

83

84

55-59

138

139

84

84

60-64

142

144

85

85

65-69

143

154

83

85

70-74

145

159

82

85

B. Physical Fitness Test: The first numbers recorded from this section of the experiment were those of standing vs. resting blood pressure. To do this a member of the lab group had to lie down on a table for five minutes. After five minutes the subjectís blood pressure was taken while he was still lying down and the numbers were recorded in Table 2. The subject remained lying down for another two minutes, stood up, and their blood pressure was taken again. The standing systolic pressure was subtracted from the resting systolic pressure and recorded in Table 2. A chart was used to determine the number of points received by the subject and recorded in Table 3.

The next part of this section is where the subjectís standing heart rate was determined. Taken by the subject was the radial artery pulse by counting the number of beats for 30 seconds. That number was multiplied by 2 to obtain the number of beats per minute. That number was recorded in Table 3. Another chart was used to determine the amount of points the subject received for this section and that number was also recorded in Table 3.

Next the resting heart rate was determined by having the subject lie down on a table for five minutes. After five minutes the subjectís pulse was taken and recorded in Table 3. Once again a chart was used to determine the number of points the subject received for this section of the experiment and the number was recorded in Table 3.

Next the Baroreceptor reflex test was given to the subject. The subject had to lie down for five minutes, stand up quickly, and record the pulse. From this number the resting heart rate was subtracted and recorded in Table 3. A chart was then used to determine the number of points the subject received for this section and recorded in Table 3.

The endurance test was the last leg of this section of the experiment. To do this the subject stepped up with one foot onto an 18 inch high surface and then brought up the other foot onto the surface. This was continued for 15 seconds, and then his pulse was taken at several intervals. First the pulse was taken right after the exercise for 15 seconds and multiplied by four. This was repeated one more time after that as well. Then the pulse was taken every 30 seconds for 120 seconds after that. The data was recorded in Table 4. The amount of time it took for the subjectís heart rate to return to normal was figured and a chart was used to award points. These heart rates were then compared to the standing heart rate. Next, the standing heart rate was subtracted from the rate taken right after exercise, and yet another chart was used to award points.

C. Investigating Heart Rate in Daphnia: Two depression slides were obtained and a small piece of cotton was placed in the center of one of the slides. Several Daphnia were placed on the slide with a pipet and the other slide was placed on top of this slide and wrapped together with a rubber band on each end. A petri dish was filled with room-temperature water, 1cm deep and the slides were placed into it. The heart of the largest Daphnia was then located under the stereomicroscope and the number of beats in 15 seconds was determined, multiplied by four, and the results placed in Table 5. Into the dish was then added ice water and the same Daphniaís heart rate was determined and recorded in Table 5. Gradually warm water was added and the heart rate was taken at five minute intervals until the normal heart rate is noted. These results were put in Table 5.

Results:

Table 1

 

Blood Pressure

Systolic

Diastolic

Trial 1

115

72

Trial 2

115

70

Trial 3

115

74

Average

115

72

Table 2

Standing vs. Resting Blood Pressure

Position

Systolic

Diastolic

Lying Down 5 min.

110

72

Lying to Standing

120

72

Change

10

0

 

Table 3

Fitness Points

Activity

Result

Fitness Points

Change in Blood Pressure

10

3

Standing Pulse Rate

78

3

Resting Pulse Rate

64

3

Baroreceptor Reflex

76

3

Heart Rate Recovery After Exercise

28

4

Heart Rate Increase After Exercise

18

2

Total Points

-

18

 

Table 4

Heart Rate After Exercise

Interval

No. of Beats

 

Heart Rate

0 to 15 sec.

24

X4=

96

16 to 30 sec.

19

X4=

76

31 to 60 sec.

35

X2=

70

61 to 90 sec.

35

X2=

70

91 to 120 sec.

35

X2=

70

 

Total Score

Cardiovascular Fitness

17 to 18

Excellent

14 to 16

Good

8 to 13

Fair

7 or less

Poor

 

Questions:

1. What changes occur in the circulatory system when a person stands up from a prone position? How do these changes affect the heart rate and blood pressure of the individual?

The circulatory system is not working very hard when a person is at rest so when that person stands up suddenly the blood pressure and heart rate of that person increase.

2. How does the circulatory system, and the heart in particular, of a conditioned athlete differ from that of a person in poor shape?

The heart of a conditioned athlete is stronger because it has been worked harder pumping more blood when that person exercises. The heart of a person in poor shape has not been worked as hard.

3. Why is high blood pressure dangerous? What health problems does it lead to?

High blood pressure is dangerous because the heart has to work to hard to push the blood through the various veins and arteries and a heart attack can occur.

4. What sort of behaviors encourage high blood pressure? Why?

Eating fatty foods and not exercising cause high blood pressure because the heart is not working hard to pump the blood, which makes it weak.

 

Table 5

 

Temperature (C)

Heartbeats per Minute

Room Temperature

200

0 to 5

84

10

160

15

152

20

204

25

200

30

212

35

216

 

Change in Metabolic Rate

 

Temperature Range

Rate of the reaction (change in heart rate)

0-10

Q10 =1.9

10-20

Q10 =1.275

20-30

Q10 =1.04

 

Questions:

1. Why does the rate of activity of ectothermic organisms increase with a rise in the temperature of its environment? How is this different from an endothermic organism?

Ectothermic organismsí body heat is determined by the environment, so their metabolic rates also change with this. Endotherms have a constant body temperature and do not change their metabolic rate strictly based on environmental conditions.

2. If this experiment were performed on a human subject, what results would you expect? Explain.

A humanís heart would also be affected by the temperature changes, but not to the extent that the Daphnia heart did.

Error Analysis: The only possible source of error in this lab would have been the slight misreading of the gauge on the sphygmomanometer.

Conclusions: Cardiovascular fitness is very important to living a healthy life. If one doesnít exercise and eat healthy foods they run a risk of being in poor shape and having a heart attack or other serious things. Heart rate and blood pressure readings can give a person a good idea about how healthy they are or how healthy they need to be. Blood pressure is so important to a personís health it is checked at every visit to the doctor or hospital.

 


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