The affect of psychological stress on the heart rate.
The human body is incredible machinery that can adjust to stressful situations and react in a “fight-or flight” manner by temporarily shutting off nonessential, at the moment, immune and digestive systems. When the body is ready for a challenge, heart rate increases, blood pressure rises and glucose production intensifies to supply large amounts of energy. These metabolic changes are caused by release of stress hormones (catecholamine and epinephrine) by adrenal glands. When stressful situation goes away, body returns to its normal state. But if the stress is chronic, the mechanism remains activated and organism is exposed to the high level of hormones for the long periods of time. As a result, blood pressure and heart rate are constantly elevated, which can take a toll on the cardiovascular system and cause a serious heart disease and even a stroke. (1) There are many studies on humans and animals that had shown detrimental affect of stress on the cardiovascular system. Like one by Andrea Sgoifo., et al., in which they compare how nonsocial and social stress controls cardiac electrical activity and come to the conclusion, that social stress results in higher possibility of ventricular arrhythmia in rats, which can be a reason for a sudden cardiac death (2). Another study on on-call physicians showed that psychological stress at working environment result in “adrenergic surge that predispose to cardiac arrhythmias” (3). Vrijkotte in her study showed how negative effect of work stress is correlated with heart rate activity and an increase in systolic blood pressure level. (4) College students are exposed to stress often more then an average person. In view of that, this experiment was conducted to investigate, how high stress level in college students contributes to the change from normal in their heart rate. We hypothesized that high stress level will increase the heart rate.
Total of 19 students of Stockton College participated in the experiment. They were e-mailed Ohio State University Medical Center stress survey. (http://medicalcenter.osu.edu/files/survey/stress.cfm) The test was composed of ten questions about personal feelings and thoughts during the last month. After completing the test, web-site generated a number, which represented the stress level. These numbers-stress levels were collected and analyzed, upon which students were divided into two categories: “Moderate stress” and “High stress”. Next, following the procedure in Lab manual (5), electrocardiogram of each student was recorded using BIOPAC 35/30. All recordings took place at 3 pm. Two electrodes were placed on the medial surface of each leg above the ankle (right leg-black lead, left leg-red lead); the third one (white) was placed on the right anterior forearm. Subjects were asked to relax for several minutes. After that, 8 second calibration procedure was performed to establish hardware internal parameters. Formation of the recognizable ECG waveform with no large baseline drift confirmed successful calibration and allowed to start recording process. First 30 second recording was taken while subject was relaxed. Second 30 seconds recording was taken immediately after performing series of standardized exercise - running for 2 minutes and 50 jumping jacks. Each subject was measured ones. ECG features - durations (P wave, PR interval, QRS interval, QT interval, ST segment, T wave) and amplitudes (P wave, QRS complex, T wave) were analyzed for three different cycles. After that, differences between before and after exercise of these dependent variables were calculated. Then, using a t-test analysis mean values, standard errors and p-values were found and then compared between “High stress” and “Moderate stress” groups.
Stress levels in students ranged from 7(the lowest) to 33 (the highest). There were nine people in...
Cited: 1. American Heart Association. 21 Apr. 2008. 21 Apr. 2008
2. Andrea Sgoifo., et al
3. Mountantonakis, Stavros E., Moutzouris, Dimitrios A., McPherson, Craig. “The impact of stress on heart rate variability of on-call physicians.” Chest (2005) 128: 277S-a. 2 Nov. 2005
4. Vrijkotte, Tanja
5. Werner Ralph. Physiology 2151 Laboratory Exercises. 2008.
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