Stress causes physiological and physical changes that can be long-term or short-term, depending on how long the stress lasts. We identify the physiological pathways and anatomical processes involved in stress, differentiate between acute and chronic stress responses, and support our findings with data from human and animal studies. Finally, in the article, an experiment to measure tension is proposed. Stress can be defined as a physiological and psychological response to unpleasant situations. Stress can be classified as acute or short-term stress, and chronic or long-term stress. Factors that trigger stress response are classified as stressors. (p.84).
Several physiological changes are initiated in response to stress. The effect on the circulatory system results in an increase in heart rate and blood pressure (p.86), through signaling to the sympathetic nervous (p.87). These changes also affect the hormonal response in the body. Secretion of adrenaline and noradrenaline hormones is increased, resulting in elevated blood glucose level. Thereafter the hypothalamus of the brain stimulates secretion of the adrenocorticotropic hormone (ACTH), which in turn causes release of cortisol from the adrenal gland (p.88). Cortisol, along with glucagon, stimulates conversion of glycogen to glucose, which is released into the blood to make the latter energy-rich for additional work (p.89). Reproductive hormones and sensation to pain are also reduced under stress (p.89). The immune system undergoes some interesting changes, as demonstrated by experiments with adrenalectomized rats. Production of T-cells was found to be enhanced in rats administered with low dosage of stress hormone corticosterone (similar to human cortisol), while those administered with a high dosage of the hormone showed a decrease in T-cell production. This demonstrated that while acute stress alerts and enhances the body’s defense mechanism, chronic stress suppresses the immune response. Over the years, several studies on both humans and model animals have further confirmed and substantiated these findings (p.91, 97-99). Small dose of acute stress has been shown to be improve memory formation, as demonstrated by studies by Gold (1986) and Cahill (1994) in human subjects (p.91-92). Studies have consistently shown stress as a beneficial and successful coping mechanism for dealing with short-term crisis (p.94-95).
Despite the physiological benefits of acute and small dose of stress, chronic stress can lead to a compromised state of the immune system, making an individual prone to diseases. Jemmott and colleagues studied stress response in dental students over the academic year and observed decreased immune marker antibodies (IgA) in the students during stressful academic period. Similar studies by Cohen and colleagues in 1991 demonstrated correlation between stress and increased susceptibility to cold (p.96-98).
Chronic stress accelerates the deposition of atherosclerotic plaques in the blood vessels, thereby increases the risk of cardiac diseases. Digestive changes triggered by chronic stress leads to increased incidences of stomach ulcers, through compromised mucosal protection of the stomach walls, and consequent increase in the potency of the bacterium Helicobacter pylori, responsible for stomach ulcers (p.100-101). Long-term stress also compromised the reproductive health of an individual. Stressed rats show decreased mating behavior; erectile dysfunction and premature ejaculation are common in human males, while human females suffer from amenorrhea and decreased sexual interest under chronic stress (p.101-102). Chronic stress correlates with reduction in number of nerve connections in the hippocampus and memory loss, through physiological changes in the brain. These deleterious effects on the brain cells are often reversible, through restoration of weeks of stress-free conditions in the subjects.
Response of the immune system (in both humans and animals) provides useful insights into the stress response of the subject. A suitable study to measure stress could therefore be designed that measures a quantifiable parameter of immune system. This can be done by measuring the level of white blood cells or quantifying amount of immunoglobulin like IgG or IgG in subjects exposed to varying degree of stress over time.

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