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The woozy feeling when standing up too quickly. After going for a run, feeling as if one more beat and the heart would project itself out of the chest. Or quite the opposite and being in a very relaxed state. These are all changes one experiences at some time or another. What causes the different feelings and how each variable affects pulse rate and blood pressure has many wondering. Because of this curiosity, an experiment was performed to get some answers.
The purpose of the experiment is to see how different variables affect pulse rate and blood pressure. Before starting the experiment, self educating on background information was a necessity in order to obtain a full understanding of what exactly was going to be performed. What is blood pressure and how does it work? “As the heart beats, the heart pushes blood through a network of blood vessels called arteries. As the blood travels through the arteries, it pushes against the sides of these blood vessels and the strength of this pushing is called blood pressure.
(Blood Pressure UK) After getting the basic definition of what blood pressure is, it was learned that when blood pressure is taken the first number that is said is the systolic blood pressure level or the highest level that is reached when the heart is squeezing. The second number that is read is the diastolic pressure level or the lowest level when the heart is relaxing, which is measured in mm Hg. (Blood Pressure UK) Moving on to pulse rate, also known as heart rate.
It is known that pulse rate is the number of times the heart beats in one minute. (Gordon) Pulse is lower at rest and increases when higher activity is performed, like exercise. (Gordon) Pulse is taken by putting the tips of the index finger and middle finger onto the palm side of the opposite wrist below the base of the thumb. (Gordon) By pressing lightly with fingers, one could feel the blood pulsing beneath the fingers. (Gordon) After counting for ten seconds, the number of beats felt is multiplied by six to get the heart rate per minute. (Gordon) Normal pulse is between sixty and a hundred beats per minute. (Gordon)
Posture Changes, Exercise, and Cognitive Stressor are the three variables to be tested. First, the focus will be on posture changes. More specifically, reclining for three minutes. It is hypothesized that both, arterial pressure and pulse rate, will decrease because the heart doesn’t have to work as hard to distribute blood to the body. Normally it takes more effort to deliver blood to the body is erect. After reclining for three minutes and standing up quickly, it is hypothesized that pulse rate will decrease because the act of standing takes a good amount of blood that travels down into the legs causing less stroke volume for the ventricle to pump. Once standing for three minutes, it is hypothesized that the arterial pressure and pulse rate with both increase. As it is increasing, it will also be recognized that the arterial pressure and pulse rate will return to baseline.
Once data is collected from the variable of posture changes, exercise will be the next variable to look at. Immediately after exercising, it is hypothesized that arterial pressure and blood pressure will increase. It is thought because the body is performing high activity, it means that the heart has to work faster to be able to successfully perform venous return which then increases stroke volume and as a result increases cardiac output. Not only will the arterial pressure and pulse rate increase, it will be at its max range. Two minutes after exercise, it is hypothesized that the arterial pressure and pulse rate will decrease. Because the body is starting to calm down and come back down to resting, the heart doesn’t need to produce as high of stroke volume therefore decreasing the cardiac output.
Focusing on the last variable of cognitive stressor, the subject will have to spell a list of words forwards and backwards. It is hypothesized that while doing this, the subject arterial pressure and pulse rate will increase. This is to be thought because while the subject is spelling the words the mind will be under a lot of stress therefore causing acts of anxiety or nervousness to arise, making the heart beat faster than normal. Procedure:
“For procedures, refer to Lab 6, Activity 2, in the Anatomy and Physiology Lab Manual.”
To start off the experiment, a baseline was needed in order to be able to compare the different variables through out the experiment. The subject was instructed to sit and relax quietly while the blood pressure cuff and pulse plethysmograph were placed properly. After the blood pressure was taken and analyzed, it was found that the subject’s blood pressure was 122/64 mm Hg and a pulse rate of 60 bpm. Now that the baseline was obtained, continuing with the changing variables could take place. Starting with the variable of postural changes, the subject first reclined for three minutes. After the two minutes, the subjects blood pressure and pulse rate was taken and gave a reading of 120/52 mm Hg and 60 bpm.
Looking back at the hypothesis, it was hypothesized that after reclining for three minutes the arterial pressure and pulse rate will both decrease. Cross referencing the given data with the hypothesis, it was found that the results didn’t fully match with the hypothesis. The blood pressure did, in fact, decrease due to the relaxation state that the subject was in. On the other hand, the pulse rate stayed the same. Reflecting on that and looking at the variables in the environment, it could be said that the subject wasn’t in a state of full relaxation. The subject was instructed to recline on a cold lab table with other subjects and groups in the room. It is possible that the discrepancy in this experiment was the environment in which the subject was instructed to recline and relax.
After reclining, the subject was instructed to stand up quickly. Right when the subject stood up, blood pressure and pulse rate were recorded. It was collected that the subject’s blood pressure was 132/58 mm Hg and pulse rate of 62 bpm. Relating back to the hypothesis, it was said that the arterial pressure and the pulse rate would decrease. The results obtained and the hypothesis did not match.
Further dissecting why the data didn’t match the hypothesis, it was discovered that because the subject stood up very quickly, 500 mL or more travels down into the legs. It was thought, due to that reason it would mean less stroke volume for the ventricle to pump. Looking at it from a different angle, because the amount of blood that travels to the legs, it actually causes the heart to work more rapidly to evenly transport regular amounts of blood through out the body causing the arterial pressure and the pulse rate to increase.
Once the subject was standing for three minutes, the reading of the blood pressure was 130/52 mmHg and the pulse rate was 64 bpm. Comparing to the hypothesis, it was said that the arterial pressure and pulse rate would increase trying to bring the body back to baseline. Looking at the results, the blood pressure, in fact, decreased and the pulse rate increased, making the results partially confirm the hypothesis. Because it didn’t completely confirm the hypothesis, it could be said that the subjects body wasn’t able to get the body completely back to baseline in three minutes. It may have taken a few more minutes in order for the body to get back to a regular state.
After those variables were explored, the next variable tested was exercise. Instead of there being only one subject, two subjects were used. Subject #1 was a well conditioned subject, someone who works out on a regular basis and already has endurance. Subject #2 was someone who was poorly conditioned, who never does strenuous activity. Before any physical activity, a baseline was required so there was data that can be compared. The well conditioned subject’s baseline was an arterial pressure of 118/70 mmHg and pulse rate of 61 bpm.
The poorly condition subject’s baseline read as arterial pressure 122/44 mmHg and pulse rate of 60 bpm. Both subjects were instructed to exercise for five minutes, which consisted of running up and down the stairs. Immediately after exercising, the reading of the arterial pressure and pulse rate were taken. The well conditioned subject’s arterial pressure read 162/62 mmHg and pulse rate of 76 bpm. The poor conditioned subject’s arterial pressure read 139/60 mmHg and pulse rate 80 bpm. The hypothesis was confirmed that immediately after exercising, the arterial pressure and pulse rate would increase. Not only would it increase, but it would be at a max range. The venous return increased due to the increase in skeletal muscle activity. Increasing venous return, increases stroke volume, which then increases cardiac output.
One minute after exercising, the subjects arterial pressure and pulse rate were recorded. Subject #1’s arterial pressure was 138/70 mmHg and pulse rate was 74 bpm. Subject #2’s arterial pressure was 134/65 mmHg and 76 bpm. The hypothesis was confirmed that the arterial pressure and pulse rate would decrease but still higher than baseline. As you see reflected in the “Results” section above, two and three minutes after exercising the blood pressure and pulse rate decreased, further confirming the hypothesis.
The third and final variable tested was cognitive stressor. The subject was instructed to read 12 spelling words forwards and backwards at five second intervals. Before, just like any experiment a baseline needed to be obtained. After the reading was recorded, the first test began. The subject had to spell a series of words, as this was happening, the subject was hooked up to iWorx which is a system that reads blood pressure and pulse rate. Once the test had ended, the data was analyzed and it was found that the hypothesis of the pulse pressure and blood pressure increasing did not apply to the first part of the test.
The subject’s blood pressure had decreased while the pulse pressure increased. The discrepancy was thought to be that the subject was very comfortable in spelling words therefore the blood pressure decreased but the pressure from spelling in front of other people may have caused the pulse rate to increase. The subject then spelled a series of words backwards, this further confirmed the hypothesis that the blood pressure and pulse pressure would increase. The focus on spelling the words backwards correctly and the pressure of people watching the subject caused the increase in blood pressure and pulse pressure.
Throughout this experiment, it was interesting to see how to different variables in every day life can effect ones blood pressure and pulse rate.
For the most part, each hypothesis was confirmed. The hypotheses that weren’t confirmed, it was an obvious discrepancy that explained why the experiment didn’t work out as planned. What can be taken from this experiment is that one can maintain a certain level of arterial pressure and pulse rate by the activity that is performed. Arterial pressure and pulse rate are very sensitive and can change at any moment. It is good to be knowledgable on what factors effect blood pressure and pulse rate; also on how it effects your body.
Blood Pressure UK:
(n.d). Retrieved from http://www.bloodpressureuk.org/microsites/u40/Home/facts/Bloodpressure
Gordon, B. (n.d.). Retrieved from http://my.clevelandclinic.org/heart/prevention/exercise/pulsethr.aspx
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