How does stress affect the body?

The autonomic nervous system (ANS) is the part of the nervous system which is responsible for regulating many aspects of the body, including digestion, respiration, and temperature. The ANS is divided between the sympathetic (SNS) and parasympathetic nervous systems (PNS). In simple terms, the SNS is responsible for getting the body ready for action, while the PNS works to relax the body.

When confronted with a stressor, the hypothalamus, located at the base of the brain, reacts in two main ways: it activates the SNS and stimulates the hypothalamic pituitary adrenal (HPA) axis (McEwen, 2007). A general overview of these two reactions is provided below.

^{Stressors trigger the hypothalamus to activate the SNS and the HPA axis. The SNS prepares the body for intense motor activity. The HPA axis helps energy to be distributed, the immune system to be suppressed, and the SNS to remain active. click to see larger version}

Impact of Stress on the Body

In situations where the individual is able to cope with the stressor, and the situation is no longer threatening, the PNS performs its role, and over time the body returns to a relaxed state. However, if an individual is subjected to a prolonged period of stress, or a chronic stressor, the body’s reaction to stress can have a negative impact on the individual’s physical wellbeing. The following negative impacts of sustained stress on the body have been identified in the literature:

• Negative effect on the digestive system, with disturbed eating habits, acid reflux, and constipation.
• Increased risk of developing cardiovascular diseases, including strokes, cardiac arrest, and coronary heart disease.
• Increased blood cholesterol levels.
• Persistent activation of the HPA axis has been linked with an impaired immune response to many different infections, including the flu and the common cold.

References

^{McEwen, B. S. (2007). Physiology and neurobiology of stress and adaptation: Central role of the brain. Physiological Reviews, 87(3), 873-904. https://doi.org/10.1152/physrev.00041.2006}