Sample Research Paper On Cardiovascular Physiology
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The different cells of the higher animals create specialized organs, tissues, and systems that have particular functions. For example, the tissue organizations that constitute the respiratory system promote breathing and, hence, allow the exchange of gases. The cardiovascular arrangement employs the blood to transport the gases, as well as other substances in the body. Additionally, the respiratory and cardiovascular systems have a close integration, such that a response to a body change in one system is manifested in the second system. The present study, therefore, investigated the cardiovascular physiology, as well as the integration of the respiratory and the cardiovascular arrangements. The procedure involved examining the Respiratory Sinus Arrhythmia, the diving reflex, and the step test. Finally, the results of the study were tabulated and discussed.
Keywords: Cardiovascular, Respiratory Sinus Arrhythmia, step test, diving reflex
The blood circulation occurs when the heart experiences the cardiac cycle, which comprises of the relaxation and contraction processes. An ineffective cardiac cycle typically lowers the blood’s circulation rate. Accordingly, the heart enters the physiological state of failure and may result in death (Fukuta & Little, 2008). In the initial cardiac cycle’s phase, the pacemaker cells typically yield an electrical signal that is distributed in the heart. The electrical stimulation allows the atrial myocardium and later the ventricles to undergo the systole phase. Subsequently, the sequential relaxation or the diastole stage occurs in the two sets of the heart chambers. The cycle of blood compression in the ventricles accompanied by the filling of the ventricle chambers initiates ventricular pressure changes. The pressure modifications close the heart’s one-way valves audibly at various intervals during the cardiac cycle. In addition, the ventricular injection of blood into the arteries during systole generates blood pressure, which is the primary driving potency of the body’s blood flow. According to Yasuma and Hayano (2004), the variability of the heart rate in synchrony with respiration induces the respiratory sinus arrhythmia (RSA). Although the RSA is the typical indicator of the heart’s vagal function, it reflects the respiratory-circulatory interactions that are observed universally among the vertebrate creatures. When a given surface of the organism’s body is immersed in cold water, an intricate respiratory-cardiovascular reaction occurs causing the diving reflex. The immersion response is highly effective and is often utilized in the stimulation of the vagus nerve, particularly in the infants (Wittmers et al., 1987). According to Hietanen (1984), the light and static activities often intensify the blood pressure and the strain on the heart more than the dynamic exercises at an equivalent level of oxygen uptake. The increased afterload causes the heart to raise its contractility and, hence, meliorates the cardiac output.
Materials and Methods
Respiratory Sinus Arrhythmia (RSA)
Nineteen subjects were selected for the study of the RSA and instructed carefully on the research protocol described by Tonhajzerova et al. (2009). They were also required to furnish written informed consent for their participation prior to the investigation. The participants were observed in an unobtrusive room, which exposed them to the standard temperature and minimal arousal stimuli, from 8:25 a.m. to about 11: 35 a.m. Moreover, the subjects were asked to lie on their backs comfortably and avoid unnecessary movements. After the initial eighteen minutes, the thoracic strap that had ECG electrodes was applied. The heart rates of the subjects during the regular breathing were determined using the ECG. Afterward, the heart rates measurements were taken during the deep breathing test.
The diving reflex is an essential adaptation, typical of the marine mammals, which helps the creatures to dive in cold water. In the process, the diminution of the heart rate occurs and results in bradycardia. Moreover, the cardiac output decreases intensely as the blood flow is deviated from the extremities and guided towards the vital organs. A relatively minor variant of the diving response in humans was demonstrated using the ECG sensors and the cold packs placed on the subjects’ faces. In the examination, a polyethylene sack was filled with ice pieces and then allowed to contact the faces of the eighteen participants, such that it covered all their facial aspects. Next, the sack was allowed to stay on their faces for fifteen seconds before the electrocardiogram was monitored. All the assessments were primarily performed with the participants inclined over the lab bench with their heads facing down and elbows resting on the desk. Furthermore, the assessments were performed with the subjects regularly breathing and when holding their breath. In the examinations that required the holding of breath, the participants were instructed to take deep breaths before holding them. Moreover, they were advised to avoid hyperventilating before holding the breaths to ensure consistent and accurate observations.
The step test was used to evaluate the cardiovascular fitness of the various subjects. Twenty-seven participants were requested to climb a staircase that consisted of eighty-two steps. Each of the steps was nearly 0.14 meters in height. The subjects were instructed to ascend the maximum number of stairs, at a pace that was suitable to them, and to stop only when they felt exhausted. Moreover, they were instructed to avoid utilizing the railing for balance. During the exercise, the oxygen saturation level and the pulse rate were monitored using a portable pulse oximeter. The number of stairs ascended and the time required to complete the procedure was recorded. The pulse rates and the oxygen saturation levels were determined in every twenty steps.
The present study focused on the sinus arrhythmia, the diving reflex, and the step test. The observations were recorded and illustrated as described in the various tables and figures.
There were two significant observations in the results of the investigation. First, the heart rate increased during the inspiration episode but declined in the expiration phase during the normal and the deep breathing tests. The second observation was that the difference between the expiration and the inspiration during the regular breathing was noticeably lower than the difference in the deep breathing test (Table 1). The observations were exemplified as presented in Figure 1 and 2.
Figure 1. Normal Breathing versus the Heart Rate. The figure shows the heartbeat variation during the two different episodes of expiration (Expir.) and inspiration (Inspir.).
Figure 2. Deep Breathing versus the Heart Rate. The graph illustrates the heartbeat variation observed during the two different episodes of inspiration (Inspir.) and expiration (Expir.).
The Figures 1 and 2 exemplify the marked difference in the heartbeats during the normal and the deep breathing activities. In the diving reflex examination, the heartbeats of the various participants were recorded during their normal breathing as presented in Table 2.
The recorded heart rates were illustrated as shown in Figure 3.
Figure 3. Time versus the Heart Rate during the Normal Breathing. The graph describes the heart rate recorded during the normal breathing before the ice bags contacted the subjects.
The ice bags’ contact with the faces of the participants elicited the diving response. When the subjects held their breath, a marked decrease in their heart rates was observed (Table 3). The unusual response, however, was not seen when the breath was held in the air. The heart rate recorded during the normal breathing was illustrated as presented in Figure 4.
Figure 4. Time versus the Heart Rate during the Normal Breathing. The figure showed the heart rate variation when the ice bags were placed on the subjects’ faces.
Figure 5. Periods of Holding Breath versus the Heart Rate. The illustration described the heart rate variation when the breath was held with the ice bags placed on the subjects’ faces.
Most of the participants completed the step test successfully without any grave complications. Some of the subjects, however, experienced exhaustion and were unable to complete the examination (Table 4). The study observations were depicted in Figures 6 and 7.
Figure 6. Time versus the Heart Rate. The diagram illustrates the variation of the heart rate during the Step exercise.
Figure 7. Time versus the Oxygen Saturation. The graph shows the level of oxygen saturation before and after the exercise.
According to Figure 7, the oxygen saturation level remained constant throughout the workout. Furthermore, the blood pressure levels of the participants during systole and diastole were evaluated and recorded as described in Table 5.
The data recorded in the Tables 5 was illustrated as depicted in the Figures 8 and 9.
Figure 8. Time versus Systolic Blood Pressure. The figure shows the variation of the systolic blood pressure with time during the step test.
Figure 9. Time versus the Diastolic Blood Pressure. The diagram illustrates the variation of the diastolic blood pressure with time during the Step Test.
According to the Figures 9 and 8, the mean diastolic blood pressure was lower than the average systolic blood pressure.
Different researchers have obtained results similar to the Table 1 data, which are demonstrated in the Figures 2 and 1. For example, Yasuma and Hayano (2004) explicate that the RSA has been shown to raise the efficacy of the pulmonary gas exchange, which suggests that the RSA has an active physiologic function. Therefore, the alveolar ventilation’s matched timing, as well as its RSA perfusion in each respiratory cycle, can lessen the energy expenditure. The stifling of unnecessary heartbeats, during the process of expiration and the ineffectual ventilation in the perfusion’s ebb, aids in the lessening of energy consumption. Furthermore, a likely dissociation exists between the RSA and the heart rate’s vagal control, which suggests the presence of differential controls between the cardiac vagal tone and the respiratory modulation of the heart’s vagal outflow (Yasuma & Hayano, 2004). Hence, the RSA is a significant physiologic phenomenon that may have a desirable impact on the gas exchange in the lungs.
According to Porges (2007), the RSA reveals the functional output of particular vagal pathways that originate from the nucleus ambiguus. Additionally, the spectrally obtained index of the vagally arbitrated heart rate variability describes the RSA as a non-invasive and sensitive index of the heart’s vagal utility. Since the respiratory arbitrated heartbeat variations are minimal during the normal breathing, the most suitable method of evaluating the RSA magnitude is the deep breathing examination (Tonhajzerova, 2009).
In animals, the diving reflex is marked by responses such as apnea (Ashok et al., 2008) and bradycardia. The reaction is further associated with the peripheral vasoconstriction, which causes the preferential perfusion of the heart and brain (Wittmers et al., 1987). The diminution of the cardiac output with a preserved or enhanced stroke volume is another response linked to the diving reflex phenomenon. Such observations were made in the present investigation (Tables 2 and 3, as well as the Figures 2, 3, 4, and 5). Caspers et al. (2011) have further noted an increase in the average arterial blood pressure in response to the diving reflex. Such cardiovascular alterations typically function to conserve oxygen for the brain and the heart. The ice bag application on the face elicits thermoregulatory vasoconstriction in both apnoea and eupnoea. Additionally, the threat of asphyxia often causes the oxygen-conserving diving reaction to dominate the thermoregulatory responses. During the breathing process, nonetheless, the diving reaction becomes obsolete and does not affect the thermoregulatory adjustments.
Figure 6 shows that the heart rate increased rapidly after commencing the step exercises because the muscles required more oxygen and energy. Consequently, the increase in the heart rate helped to circulate oxygen to the muscles and the generated carbon dioxide to the lungs. In the step test, the oxygen level remained constant (Table 4 and Figure 7) because the oxygen saturation characteristically ranges between ninety-four to ninety-eight percent irrespective of whether the body is at rest or being exercised. Moreover, a saturation of less than ninety percent for a prolonged duration can cause serious health risks. Thus, the step test failed to influence the oxygen saturation level. Typically, the diastolic blood pressure is lower than the systolic blood pressure (Brzezinski, 1990) as observed in the Table 5, as well as the Figures 9 and 8. Thus, the blood pressure is presented as the systolic pressure divided by the diastolic pressure.
The examination of the hemodynamic reactions to workouts offers an unparalleled opportunity to integrate and analyze the cardiovascular physiology (Patil et al., 1993). As a result, the researcher gains more understanding of the operations of the cardiovascular system when exercising the body.
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