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Anatomy and Physiology Lab Six: Blood Pressure and Pulse
BIOL 204, Section 550
Lab Report By:
April 17, 2013
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INTRODUCTION
Blood pressure, or BP, is the “force per unit area exerted on a vessel wall by the
contained blood”, whereas pulse is the “rhythmic expansion and recoil of arteries resulting from
constriction”. In a healthy adult, blood pressure would be 120/80 (measured in millimeters of
mercury, or mmHg). The top figure refers to the systolic pressure, which is the pressure placed
on blood vessel walls by the blood during a ventricular contraction. The bottom number refers to
the diastolic pressure, or the pressure reached during vessel relaxation (the lowest point of the
cardiac cycle). (Marieb & Hoehn, 2010)
The mean arterial pressure, or MAP, is the pressure that pushes the blood to various
tissues (Marieb & Hoehn, 2010). MAP is the product of the cardiac output and the resistance
(Chandran et al, 2012). Resistance is the “opposition to flow and is a measure of the amount of
friction blood encounters as it passes through the vessels” (Marieb & Hoehn, 2010). Cardiac
output (CO), alternatively, is defined as the volume of blood propelled by each ventricle in one
minute (Marieb & Hoehn, 2010). CO is the product of stroke volume and heart rate (Marieb &
Hoehn, 2010). Stroke volume, somewhat similar to cardiac output, is the amount of blood
pushed out by one ventricle in a single beat (Marieb & Hoehn, 2010). It can be calculated by
taking the difference of the end diastolic volume and the end systolic volume (Marieb & Hoehn,
2010). The end diastolic volume is the volume of blood that gathers in a ventricle during
diastole (“relaxation”), while the end systolic volume is the amount of blood lingering in a
ventricle after the ventricle has contracted (Marieb & Hoehn, 2010).
The regulation of heart rate and stroke volume is controlled by many factors, with the
autonomic nervous system playing a central role. The autonomic nervous system is made up of
the sympathetic and parasympathetic nervous systems that either increase (sympathetic) or
decrease (parasympathetic) the heart rate, depending on the situation. When a person, like the
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test subjects for several of the experiments completed in lab, is confronted with situations where
they are emotionally or physically stressed, such as exercise or anxiety, the cardioacceleratory
center communicates to the sympathetic nervous system and the heart rate increased. Conversely,
after the physical or emotional stressor has subsided, the cardioinhibitory center sends a signal to
the parasympathetic nervous system to reduce the heart rate so the person can relax. (Marieb &
Hoehn, 2010)
The purpose of lab six, entitled Blood Pressure and Pulse is to demonstrate blood
pressure and pulse rate changes with different postures, activity levels via exercise, and even
stress from cognitive activity. When observing blood pressure and pulse changes in posture, it is
hypothesized that the test subject’s arterial pressure and pulse will both decrease after reclining
for two to three minutes because their heart does not have to work as hard to pump blood to the
rest of the body since the subject is relaxing. Likewise, when the subject stands up quickly after
laying for three minutes, it is predicted that their pulse and arterial pressure will also decrease
since blood will rapidly rush to their lower body. Finally, when the subject stands at attention
for two to three minutes, their arterial pressure and pulse will increase since they have to ‘work’
harder to stand straight for that amount of time.
In the portion of the experiment involving vigorous exercise, it is hypothesized that
arterial pressure and pulse will increase immediately after exercising for both subjects (well and
poor conditioned) because blood pumps much faster as a person engages in cardiovascular
activities. After one, two, and three minutes post exercise, however, the arterial pressure and
pulse rate should decrease and return to the baseline for both subjects. The well conditioned
subject should return to their resting heart rate faster than the poorly conditioned subject since
they have trained their body to handle the extra exertions related to exercise.
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The final experiment in lab six was observing changes in pulse and blood pressure related
to cognitive stress. It is hypothesized that the test subject’s pulse rate and blood pressure will
increase as they exert mental effort to spell twelve words both forward and backwards. Since
their fellow classmates are observing their every spelling, the subject’s sympathetic nervous
system could be activated and they may feel added pressure as they attempt to spell each word
perfectly.
PROCEDURE
For procedures, refer to Lab 6, Activity 2, in the Anatomy and Physiology Lab Manual.
RESULTS
Part I: Proper Use of the Sphygmomanometer
Trial
Number
1
2
Systolic Pressure (mmHg)
118
120
Diastolic Pressure (mmHg)
80
84
Pulse Rate (bpm)
78
70
Part I: Proper Use of the Sphygmomanometer
140
120
100
80
Trial 1
60
Trial 2
40
20
0
Systolic Pressure (mmHg)
Diastolic Pressure (mmHg)
Pulse Rate (bpm)
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Part II: Effect of Postural Changes
Posture
Pulse Rate (bpm)
Blood Pressure (mmHg)
Sitting Quietly (Baseline)
72
100/65
Reclining (after 2-3 minutes)
68
95/70
Immediately Upon Standing
76
120/83
After Standing for 3 Minutes
76
118/90
Part II: Effect of Postural Changes - Pulse
Rate (bpm)
80
75
70
Pulse Rate (bpm)
65
60
Sitting Quietly Reclining (after Immediately After Standing
(Baseline)
2-3 minutes) Upon Standing for 3 Minutes
Part III: Exercise
Well Conditioned Subject
Heart Rate (in bpm)
Blood Pressure (in mmHg)
Baseline
76
118/78
Immediately
92
130/80
1 Minute
82
125/79
2 Minutes
75
100/68
3 Minutes
70
118/75
Poor Conditioned
Heart Rate (in bpm)
Blood Pressure (in mmHg)
Baseline
88
108/72
Immediately
108
130/68
1 Minute
96
120/70
2 Minutes
95
108/68
3 Minutes
88
110/72
Fitness
Index*
66
54
Part III: Exercise - Heart Rate (bpm)
120
100
80
60
40
Well Conditioned HR (in bpm)
20
Poor Conditioned HR (in bpm)
0
*Fitness Index =
Duration of Exercise (sec) x 100
2 x {sum of three pulse counts in recovery}
(Chandran et al, 2012)
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Part IV: Cognitive Stressor
Condition
Max
Min Mean Systolic Diastolic
HR
HR
HR
BP
BP
(bpm) (bpm) (bpm) (mmHg) (mmHg)
Pulse
pressure
(mmHg)
Mean
Arterial
Pressure
(mmHg)**
Baseline 1
84
77
82
114
82
32
92.7
Spell Forward
105
92
99.5
127.6
85.6
42
99.6
Spell Backwards
115
97.6
101
139
78
101
111.7
Part IV: Cognitive Stressors - Heart Rate
(bpm)
140
120
100
80
Baseline 1
60
Spell Forward
40
Spell Backwards
20
0
Max HR (bpm)
Min HR (bpm)
Mean HR (bpm)
Part IV: Cognitive Stressors - Blood
Pressure (mmHg) and Pulse Pressure
(mmHg)
160
140
120
100
80
60
40
20
0
Baseline 1
Spell Forward
Spell Backwards
Systolic BP (mmHg)
Diastolic BP (mmHg)
Pulse pressure
(mmHg)
**MAP = Diastolic Pressure + Pulse Pressure/3
(Marieb & Hoehn, 2010)
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DISCUSSION
The experiments proved to be quite informative when the data is compared to the various
hypotheses. To analyze this further, several pathways based on the Mean Arterial Pressure, or
MAP, can explain the blood pressure and pulse changes during the experiments. MAP, as stated
in the introduction is, calculated by multiplying the cardiac output by the resistance (Chandran et
al, 2012). By looking at cardiac output (CO), “the product of the heart rate and stroke volume”,
one can further understand the differences in arterial pressure and pulse for the experiments
(Marieb & Hoehn, 2010). First, it is important to note that both heart rate and stroke volume are
directly related to cardiac output (Marieb & Hoehn, 2010). This means that if one or both of the
factors increased or decreased, cardiac output would do the same (Marieb & Hoehn, 2010).
In the first experiment illustrating the relationship between posture changes to arterial
pressure and pulse, the hypotheses did not quite reflect the final results. While the hypothesis
that the subject’s blood pressure and pulse would decrease after reclining and increase after
standing at attention were correct (the blood pressure and pulse rate decreased and increased,
respectively), the hypothesis regarding the pulse and blood pressure after standing immediately
from reclining did not match the final data. Both the blood pressure, 120/83 mmHg, and pulse,
76 bpm, increased instead of the expected decrease when the test subject quickly stood up after
lying down compared to the baseline blood pressure and pulse rate (100/65 mmHg and 72 bpm,
respectively). According to Yokoi and Aoki, “ When we suddenly change from a supine
position to a head-up tilt (90 degree) position without the muscle pump being activated, some
portion of blood (500-600 mL) moves into the veins of the legs, and another 200-300mL into the
buttocks and pelvic area. The resultant reduction of cardiac output may cause a fall in arterial
blood pressure” (1999). Since our results did not match their experiments, perhaps the
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sympathetic nervous system was involved. As the test subject stood up, there was a rush of
excitement, which then caused the sympathetic nervous system to discharge norepinephrine and
increase the heart rate (Marieb & Hoehn, 2010). This, in turn, caused a chain reaction, also
increasing the cardiac output and then the mean arterial pressure (Marieb & Hoehn, 2010).
In the first portion of the first experiment where the test subject was reclining, the heart
rate declined from 72 bpm to 68 bpm, probably due to the heart not having to work as hard since
the test subject was lying down. Stroke volume, the other component of cardiac output, may
have decreased in this situation, since the amount of venous return, “the amount of blood
returning to the heart” (Marieb & Hoehn, 2010), decreased, causing a decrease in the end
diastolic volume (Chandran et al, 2012). A decline in the strength of the ventricular contractions
caused an increase in the end systolic volume, also contributing to the decreased stroke volume
(Chandran et al, 2012). The decrease in stroke volume caused a decrease in the cardiac output,
which then caused a decrease in the mean arterial pressure (Marieb & Hoehn, 2010).
The final portion of the first experiment showed an increase in the subject’s heart rate,
from 72 bpm to 76 bpm, and blood pressure, from 100/65 mmHg to 118/90 mmHg. The test
subject’s body may have been under some stress while standing at attention for several minutes.
The stress signals the sympathetic nervous system to release norepinephrine, increasing the heart
rate (Marieb & Hoehn, 2010). This will increase the cardiac output and the mean arterial
pressure (Marieb & Hoehn, 2010).
The second experiment connecting the effects of exercise with the changes in pulse rate
and arterial pressure appeared to be similar to the hypotheses. In both the poor and well
conditioned subjects, their blood pressure and heart rate went up from their baseline immediately
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following exercise, but decreased steadily one, two, and three minutes post exercise. As it was
expected, the well conditioned subject’s heart rate and blood pressure increased less than the
poorly conditioned subject immediately following exercise. The well conditioned subject was
also able to recover faster than the poor conditioned subject, showing a lower heart rate and
blood pressure after two minutes (from 92 bpm and 130/80 mmHg immediately following
exercise to 75 bpm and 100/68 mmHg two minutes after exercise). The poorly conditioned
subject’s heart rate took the full three minutes to return to their normal 88 bpm, but their blood
pressure three minutes post exercise (110/72 mmHg) was still higher than their resting blood
pressure (108/72 mmHg). Interestingly enough, when both of the test subjects fitness index was
analyzed, the ‘well conditioned’ subject’s index of 66 only fell in the ‘average’ category (a range
of 63-71) while the poor conditioned subject’s index of 54 (any index below 55 was considered
‘poor physical condition) was to be expected (Chandran et al, 2012).
Relating the results of this experiment to the pathway involving the heart rate can explain
the increase of both test subjects. As a person exercises the sympathetic nervous system is
activated, secreting norepinephrine at the cardiac synapses (Marieb & Hoehn, 2010). This
triggers the pacemaker of the heart more quickly, with the heart’s response to also beat more
rapidly (Marieb & Hoehn, 2010). This reaction increases the cardiac output, and in turn, the
mean arterial pressure (Marieb & Hoehn, 2010). The condition of the subject shows how fast
their heart rate and blood pressure return to normal, as shown in the experiment.
The data from the final experiment utilizing cognitive stressors correspond to the
hypothesis that the subject’s blood pressure and pulse rate would increase while spelling words
forward and backward. Spelling the words backwards appeared to put more stress on the subject
since all of the variables increased more than spelling the words forward. While spelling the
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twelve words forward increased the mean heart rate from 82 bpm to 99.5 bpm, spelling the
words backward increased the mean heart from from 82 bpm to 101 bpm. The mean arterial
pressure during this experiment also increased considerably from the baseline, 92.7 mmHg, to
spelling the words forward (99.6 mmHg), then backwards (111.7 mmHg).
Utilizing the same pathway used in the exercise experiment, the sympathetic nervous
system is activated when there are emotional stressors, like anxiety, in addition to the physical
stressors such as exercise (Marieb & Hoehn, 2010). Some students may find that spelling words
forwards and backwards in front of their fellow classmates to be stressful, which can provide a
signal from the sympathetic nervous system to emit norepinephrine, causing the pacemaker to go
off more quickly which in turn causes the heart to beat rapidly (Marieb & Hoehn, 2010). There
is an increase in the cardiac output and the mean arterial pressure as well (Marieb & Hoehn,
2010).
Although the data appears to be somewhat accurate, there may have been a few reasons
for the data discrepancies. One may speculate that since the Anatomy and Physiology lab
students were novices at manually taking blood pressure and pulse that the readings may be
slightly off. Also, taking the test subject’s blood pressure multiple times appeared to make the
subject’s blood pressure and pulse rise during the experiments. In order to make the experiments
cleaner and avoid some data discrepancies, the directions should state to switch the arm in which
the blood pressure and pulse are taken. This may avoid some of the incorrect reading that
occurred after retaking the test subject’s blood pressure multiple times, causing stress (and
possible discomfort) to the students involved. Also, in the first experiment relating posture
changes to arterial pressure and pulse rate, it may be a good idea to provide some sort of
reclining chair for the test subject to lie down, then easily stand up. The test subject for that
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experiment used the lab table to lie down, but found it difficult to stand up quickly once the three
minutes of lying down were complete. Overall, the many experiments that made up lab six
clearly highlighted how heart rate and pulse can be affected by different situations, whether it is
standing at attention or attempting to spell a few words backwards.
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WORK CITED
Chandran et. al. (2012). Human Anatomy & Physiology: BIOL 204 Laboratory Manual 20122013. pp. 6.1-6.26.
Marieb, E. N., & Hoehn, K. (2010). Human Anatomy & Physiology. San Francisco: Benjamin
Cummings.
Yokoi, Y., & Aoki, K. (1999). Relationship between blood pressure and heart-rate variability
during graded head-up tilt. Acta Physiologica Scandinavica, 165(2) pp. 155-161.