Organs Involved in the Stress Response
The endocrine system and the nervous system are so closely related that they are often lumped into a single system: the neuroendocrine system. This system deals with chemical communication in the body via hormones, which work in conjunction with the nervous system. The goal of the nervous system is to bring homeostasis to all internal responses, which helps keep the body healthy and protected. Within the endocrine system is the famed HPA axis, a complex set of interactions between the hypothalamus, pituitary, and adrenal glands. The hypothalamus (H) is the command center of the brain, often called our “god center.” This area of the brain communicates with the rest of the body through the autonomic nervous system and through influxes of hormones. It oversees and assesses everything going on in the body, then informs its “personal assistant,” the pituitary (P) gland, what to do. The personal assistant informs the “general managers” (the target organs), which then enlist the “workers” (particular biochemical processes) in the relevant tissues or organs of the body. The enlisted or activated tissues include the visceral organs—heart, lungs, intestines, kidneys, liver, and pancreas—as well as many lesser-known parts of the body such as the gallbladder, spleen, blood vessels, and skeletal muscles.
Sympathoadrenal System
The connection between the hypothalamus, the adrenal medulla, and the sympathetic nervous system is referred to as the sympathoadrenal system (SAS).
Stress Hormones
This section describes the different hormones secreted within the endocrine system and how they are triggered by the stress response. Cortisol, one of the better-known stress hormones and the primary hormone released from the adrenal glands, is often called the “stress hormone.” When cortisol is secreted, it causes a breakdown of muscle protein, leading to the release of amino acids into the bloodstream. Amino acids are processed by the liver to synthesize glucose. This process raises blood sugar levels in the brain, which gives us energy. At the same time, the other tissues in the body decrease their use of glucose. Cortisol also leads to the release of fatty acids for use by the muscles. The processes directing and replenishing energy prepare the body to manage stress and ensure that the brain receives adequate energy sources. Another important purpose of cortisol in the body is the regulation of blood pressure and cardiovascular functions. It also assists the immune system in responding to infection and inflammation. Cortisol levels are at their highest in the morning.
When the Natural Stress Response Goes Haywire
The body’s stress-response system is usually self-limiting. Once a perceived threat has passed, hormone levels return to normal. As adrenaline and cortisol levels drop, your heart rate and blood pressure return to baseline levels, and other systems resume their regular activities. But when stressors are always present and you constantly feel under attack, that fight-or-flight reaction stays turned on.
The Results of Unmanaged Stress
Overadaptation to stress and disruption of the HPA axis’s flow are at the core of many health issues. For example, when the HPA axis is strong, your body is usually able to handle even high levels of stress. A strong HPA axis is also helpful for pregnant women, women who have just given birth, and women in menopause. Over time, the repeated activation of stress hormones, aka the fight-or-flight response, can take a serious toll on the body. Research suggests that chronic stress contributes to high blood pressure, promotes the formation of artery-clogging deposits, and causes brain changes that may contribute to anxiety, depression, and addiction. Preliminary research suggests that chronic stress may also contribute to obesity, both directly (causing people to eat more) and indirectly (decreasing sleep and exercise).
Chronic stress and the oversecretion of cortisol and other stress hormones can disrupt almost all of the body’s processes. Overexposure to cortisol can cause numerous health problems. One well-known problem is adrenal fatigue. Adrenals produce and control the release of cortisol. When the adrenals chronically secrete cortisol and other stress hormones, your adrenals stop producing cortisol, leading to adrenal fatigue. Adrenal fatigue is a term often used by health professionals to describe the phenomenon of the adrenal glands running on empty and the resulting mental and physical state of those experiencing it. During stressful periods, our glands release high levels of cortisol, which is the most important hormone we have to help the body manage stress. Think of cortisol as our own built-in alarm system, alerting us when the body is in danger. It also works with certain parts of the brain to control mood, motivation, and fear. If too much cortisol is secreted, many bodily processes begin to underperform, potentially resulting in illness.
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