In today’s fast-paced world, stress has become a part of our lives. Small doses of stress can be a good thing, enabling us to stay focused and alert. However, with work pressures, financial strains, and personal challenges, chronic stress is becoming common nowadays. In today’s post, we will discuss the physiological changes that happen when the body is under stress. It is important to understand these changes to fully comprehend the impact of stress on the body.
When the body is faced with an acute stressor, such as a sudden noise or an accident, it triggers a reaction known as the “fight or flight” response [1,2]. In a split second, the hypothalamus (located in the brain) sends a signal to the adrenal glands (located on top of the kidneys) to release epinephrine (a.k.a. adrenaline) and norepinephrine. These hormones increase the heart rate, blood pressure, and respiration to increase blood flow to the muscles and brain [1,2]. Moreover, they release glucose and fatty acids from the liver and adipose tissue, providing additional energy to the muscles [1]. All these responses provide the body with a burst of energy to respond to the perceived danger [3].
At the same time, a slower response is mediated by the hypothalamic-pituitary-adrenal (HPA) axis [1,4]. When the body experiences stress, the hypothalamus releases a hormone called corticotropin-releasing hormone (CRH). The CRH signals the pituitary gland which releases adrenocorticotropin hormone (ACTH), which then travels through the bloodstream to the adrenal glands. In response to ACTH, the adrenal glands release another hormone: cortisol. Cortisol is an essential hormone that affects almost every organ in the body [5]. It plays many important roles, such as [6]:
Maintaining energy supply by controlling the body’s use of fats, proteins, and carbohydrates.
Inhibiting the immune system.
Regulating blood pressure.
Regulating blood sugar.
Helping control the sleep-wake cycle.
Once the cortisol levels in the body reach a certain point, there is negative feedback sent to the hypothalamus and pituitary gland to inhibit the release of CRH and ACTH, maintaining homeostasis [1,4].
All these responses help the body to cope with the stressor faced at that moment and return to a normal state once it has passed. But what happens if this system does not stop producing cortisol and the body stays in a state of chronic stress? Stay tuned for next’s week post where we will delve deeper into the effects of chronic stress on our health.
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Written by: María
Edited by: Natasha
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References:
Chu, B. et al. (2022) "Physiology, Stress Reaction", StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK541120/
Fight-or-flight response | Definition, Hormones, & Facts (2023). Britannica. Available at: https://www.britannica.com/science/fight-or-flight-response (Accessed: 23 April 2023).
Understanding the stress response (2011). Harvard Health. Available at: https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response (Accessed: 23 April 2023).
Smith, S. and Vale, W. (2006) "The role of the hypothalamic-pituitary-adrenal axis in neuroendocrine responses to stress", Dialogues in Clinical Neuroscience, 8(4), pp. 383-395. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3181830/
Thau, L., Gandhi, J. and Sharma, S. (2022) "Physiology, Cortisol", StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK538239/
Cortisol: What It Is, Function, Symptoms & Levels (2023). Cleveland Clinic. Available at: https://my.clevelandclinic.org/health/articles/22187-cortisol (Accessed: 23 April 2023).
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