Physiology of the Cardiovascular and Respiratory Systems

Exercise Physiology Practical Report 2018

Introduction                                                                                                

This report outlines the results and analysis of an experiment to study the physiology of the cardiovascular and respiratory systems and how they respond to short periods of exercise.

The cardiovascular system consists of three major components: blood, the heart and blood vessels (Tortora and Derrickson, 2017, p.6) and during short periods of exercise (in this case cycling), whether the oxygen demands are met depends on the cardiac output. Cardiac output is the amount of blood the heart pumps out of the ventricles into the aorta per minute (Hill and Olson, 2012). During exercise, the heart pumps faster as a result of high blood pressure to enable sufficient cardiac output, which helps deliver greater volumes of oxygen to active muscle tissues where there is a higher demand. The reason behind heart rate increasing with exercise is due to neural and hormonal control. During exercise, parasympathetic nervous activity is reduced, and sympathetic nervous activity is increased via the sinoatrial node (SAN) which results in the heart rate increasing (Birch, McLaren and George, 2004). The heart also oxygenates blood by returning it to the lungs via blood vessels for gas exchange to occur.In addition, the respiratory system which includes the lungs and the air pathways such as the trachea, bronchi and the pharynx also responds to physical activity. When exercising, greater oxygen must be transported through the blood vessels. Exercising stimulates increased ventilation (Birch, McLaren and George, 2004) and so alongside an increased heart rate, the rate and depth of breathing increases (Hoefs, 2017). This is to make sure that more oxygen is absorbed into the blood and more carbon dioxide is being expired.

Pulse pressure is the difference between maximum pressure your heart exerts while beating (systolic pressure), and the amount of pressure in your arteries between beats (diastolic pressure) (nhs.uk, 2016). Due to increased stroke volume (volume of blood pumped from the left ventricle), pulse pressure increases during exercise.

Aim

To identify how the human respiratory and cardiovascular system responds to 15 minutes of rest and exercise physiologically, in particular observing the respiratory rate, pulse pressure and the volume of expired carbon dioxide.

Hypothesis

During periods of exercise, the respiratory rate will increase resulting in higher pulse pressure and a greater volume of carbon dioxide being expired.

Results

The data that was collected was for 64 participants however 18 participants were excluded from the final data.  This was because it was incomplete and since three variables were being measured, the overall effects on the cardiovascular and respiratory systems could not be determined as the three are linked – with pulse pressure and expired CO₂ increasing when respiratory rate increases.

Figure 1: This is a mean ± standard deviation graph for the respiratory rate per minute for all 46 participants. This includes the resting, exercising and recovery values. The resting period was between 1 to 4 minutes followed by the exercise phase which started at 5 minutes and ended at 10 minutes, where the recovery period started.

Figure 1 depicts that the average resting respiratory rate for the participants is between 15 and 28 breaths per minute. Whilst data shows that the normal accepted range is 12 to 20 breaths per minute (Resus.org.uk, 2015), the slight difference could be due to varying ages and health of the participants. Figure 1 also indicates that average respiratory rate significantly increased during the exercise phase and began to decrease post-exercise and despite being very close, did not quite reach the resting values. The data has been presented in a mean ± standard deviation graph to show an overall trend.

As demonstrated by figure 2, the average pulse pressure for the participants was between 28 and 52 mmHg at rest which quickly increased to 30-68 mmHg when exercising. The pulse pressure steadily returned back to the resting values during the recovery phase. The increase in pulse pressure during the exercise period correlates with the higher respiratory rates during exercise shown in figure 1. The data has been presented in mean ± standard deviation graph to show an overall trend.

Figure 3: This mean ± standard deviation bar graph shows the expired CO₂ (as a %) at rest and during exercise. The resting period was between 1 to 4 minutes followed by the exercise phase which started at 5 minutes and ended at 10 minutes, where the recovery period started.

Figure 3 demonstrates the percentage of carbon dioxide being expired and shows that during the resting phase less carbon dioxide was being exhaled than during the exercise phase. At rest, the percentage of carbon dioxide being expired was between 1.2 and 3.4% whereas during exercise, the percentage of carbon dioxide being exhaled was between 2.2 and 4.5%. On comparison with figure 2, it can be determined that as pulse pressure increased, a greater percentage of carbon dioxide was being expired. The data has been presented in a mean ± standard deviation bar chart to allow comparison of two data sets.

Discussion

Overall, the hypothesis has been supported by the data collected during this experiment. As shown in figure 1, the respiratory rate per minute did increase overall during exercise when compared to the initial resting values and then decreased after exercise. Although 18 participants were excluded from the final data, it is clear that there was a positive trend on the whole. Furthermore, pulse pressure was hypothesized to increase alongside respiratory rate during exercise and the return to resting values afterwards. This can be confirmed in figure 2, as the increase in pulse pressure correlates with the increase in respiratory rate shown in figure 1. In conjunction with pulse pressure, the volume of carbon dioxide expired was also hypothesized to increase during exercise and then return back to normal resting values afterwards.

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This was anticipated because when exercising, a greater volume of oxygen must be transported through the blood vessels. Exercising causes the heart rate to increase and stimulates increased ventilation (Birch, McLaren and George, 2004). This is so the rate and depth of breathing increases to ensure more oxygen is reaching the active tissue cells for respiration to occur more efficiently. It is known that carbon dioxide is a by-product of respiration and that during exercise more carbon dioxide is exhales so that more oxygen is being transported to the respiring muscle cells.

There are many factors that could possibly cause variation in the responses of the cardiac and respiratory systems to exercise. The two main factors that are known to affect the cardiovascular and respiratory responses are gender and age. Heart rate is age dependent and so aging will reduce cardiac output and maximum performance of the cardiac and respiratory systems(Birch, McLaren and George, 2004). Studies have shown that gender also plays a role in varying responses to exercise. This is because females are most typically smaller in size compared to males and so therefore have a smaller lung surface area to volume ratio. This means that their respiratory rate per minute is higher than males, due to the fact that their lungs inhale/exhale a smaller volume of gas to be transported to and from respiring cells, resulting in more breaths per minute. Another factor that could cause variation in the responses of the cardiac and respiratory systems to exercise is any related illness/disease, for example asthma. Usually, people breathe in through their noses, so the air is warmed and moistened. Whilst exercising, there is a tendency to breathe faster and in through the mouth, so the air being inhaled is colder and drier. For severe asthmatic sufferers, “the airways are sensitive to these changes in temperature and humidity and they react by getting narrower” (Asthma UK, 2016). This means that asthmatic sufferers have a higher respiratory rate in comparison to healthy individuals and also cannot participate in high intensity or long periods of exercise.

Additionally, there are some changes that could be applied to the experimental method in order to make it more informative. This includes ensuring there is enough time and participants so that no data is left incomplete thus creating a bigger sample size which improves reliability and makes it more informative as well. Moreover, perhaps conducting some more background research of the chosen participants in terms of their daily/weekly exercise could make this experiment more informative. This would be beneficial as a comparison could be carried out between healthy individuals who exercise more and those that exercise less in order to identify the varying responses of the respiratory and cardiovascular systems.

The resources chosen to be referenced in this practical report were done so after critically analysing each bit of information that was considered to be of good use for the background knowledge of this experiment. The fact that the information provided linked to the data collected in this experiment indicates the reliability and accuracy of the resources referenced in this report.

In conclusion, the overall success behind this exercise physiology experiment was down to the fact that it was conducted in a group setting which allowed for efficient use of time. Perhaps for future experiments every member of the groups should record the results to prevent any incomplete/missing data.

BIBLIOGRAPHY

• Tortora, G. and Derrickson, B. (2017). Principles of Anatomy and Physiology. New York: Wiley, p.6.
• Hill, J. and Olson, E. (2012). Fundamental Biology and Mechanisms of Disease. 1st ed. Elsevier Science, Chapter 6.
• Birch, K., McLaren, D. and George, K. (2004). Sport and Exercise Physiology. 1st ed. Oxford: Bios Scientific Publishers Ltd, p.88.
• Birch, K., McLaren, D. and George, K. (2004). Sport and Exercise Physiology. 1st ed. Oxford: Bios Scientific Publishers Ltd, p.67.
• Hoefs, J. (2017). Response of the Respiratory System to Exercise. [online] Livestrong.com. Available at: https://www.livestrong.com/article/376756-response-of-the-respiratory-system-to-exercise/ [Accessed 16 Nov. 2018].
• nhs.uk. (2016). What is blood pressure? [online] Available at: https://www.nhs.uk/common-health-questions/lifestyle/what-is-blood-pressure/ [Accessed 16 Nov. 2018].
• Resus.org.uk. (2015). ABCDE approach. [online] Available at: https://www.resus.org.uk/resuscitation-guidelines/abcde-approach/ [Accessed 17 Nov. 2018].
• Birch, K., McLaren, D. and George, K. (2004). Sport and Exercise Physiology. 1st ed. Oxford: Bios Scientific Publishers Ltd, p.88.
• Birch, K., McLaren, D. and George, K. (2004). Sport and Exercise Physiology. 1st ed. Oxford: Bios Scientific Publishers Ltd, p.87.
• Your Bibliography: Asthma UK. (2016). Exercise as an asthma trigger | Asthma UK. [online] Available at: https://www.asthma.org.uk/advice/triggers/exercise/ [Accessed 19 Nov. 2018].