Anxiety, The Brain, The

When it reacts to challenges, your body plays a predetermined role. You breathe harder, your pulse quickens, and your muscles stiffen as you ready to act. These emotions may have helped our ancestors flee predators, but any stressful event — fighting with your parents, a blind date, a looming deadline at work, stomach pains, finding your apartment was stolen, or attempting karaoke for the first time — might set them off. This is known as the stress response, and your body activates it to some extent in response to any external or internal danger to homeostasis.

The Stress Reaction

The stress response connects three parallel communication networks in the brain, coordinating the action of the voluntary and involuntary nerve systems, muscles, and metabolism to accomplish a single protective aim.

Messages from the somatic (voluntary) nerve system to muscles prepare the body to fight or flee danger (the fight-or-flight response). Autonomic (involuntary) nervous system messages provide nutrients and oxygen to those muscles. The sympathetic branch instructs the adrenal medulla to produce the hormone epinephrine (commonly known as adrenaline), which causes the heart to beat faster and relaxes the artery walls that provide blood to muscles, allowing them to react quicker.

At the same time, the parasympathetic branch of the autonomic nervous system reduces blood flow to other organs such as the skin, gonads, digestive tract, and kidneys. Finally, a cascade of neuroendocrine hormones originating in the hypothalamus and anterior pituitary circulates in the circulation, influencing functions such as metabolic rate and sexual function and instructing the adrenal cortex to produce glucocorticoid hormones such as cortisol.

Glucocorticoid hormones link to several bodily tissues and have wide-ranging actions that prepare the body to react to future threats. These hormones increase the creation and release of sugar from storage locations such as the liver, therefore providing energy to muscles. They also bind to parts of the brain that increase attention and learning. And they aid in the suppression of non-essential activities like as development and immunological responses until the crisis is over.

It's simple to see how (and why) these physiological changes cause your body to become aware and ready for action. When it comes to stress, though, your body cannot distinguish between the risk of confronting a bull elephant and the aggravation of being delayed in traffic. When you are under chronic stress, your adrenal glands continue to produce adrenaline and glucocorticoids. Long-term exposure to these hormones has been demonstrated in several animal and human studies to be harmful.

Stress that is ongoing

Excessive glucocorticoid exposure may harm a variety of physiological systems. It may induce muscular atrophy, force the body to store energy as fat, and maintain blood sugar levels excessively high, all of which can exacerbate diabetic symptoms. Excess glucocorticoid exposure also leads to the development of hypertension (high blood pressure) and atherosclerosis (artery hardening), increasing the risk of heart attack. Because hormones suppress immune system activity, they weaken resistance to infection and inflammation, sometimes causing the immune system to target the body's own tissues.

Chronic stress may have a deleterious impact on brain tissue and function. Consistently high levels of glucocorticoids impede neuron development inside the hippocampus, affecting normal memory formation and recall processes. Stress hormones may also block neuronal pathways involved in decision-making and cognition, speeding up the degradation of brain function caused by ageing. They may exacerbate the effects of a stroke. They may also cause sleep difficulties since cortisol is a key wakeful signal in the brain, therefore high cortisol levels caused by chronic stress may cause sleep delays. Stress-induced insomnia may then set in motion a vicious cycle in which the stress of sleep loss causes the production of even more glucocorticoids.

Because glucocorticoids play key roles in brain development, the consequences of prolonged stress may extend beyond a single person. If a pregnant woman experiences persistent stress, the higher stress hormones may cross the placenta and alter her fetus's developmental trajectory. Glucocorticoids are transcription factors that may bind to DNA and change which genes express proteins. Animal studies have shown that mothers with high glucocorticoid levels during pregnancy had kids with lower birth weights, developmental impairments, and more sensitive stress reactions throughout their lives.

Because metabolic stresses such as malnutrition create high glucocorticoid levels, it has been proposed that these hormones may assist prepare the baby for the environment it will be born into. Tough, stressful conditions force foetuses to develop stress-sensitive "thrifty" metabolisms that readily store fat. Unfortunately, these stress-sensitive metabolisms raise a person's chance of acquiring chronic metabolic illnesses like obesity or diabetes, particularly if they grow up in lower-stress surroundings with plenty of food.

Stress may even be passed on to future generations through epigenetic pathways. Chronic stress may alter the markers on DNA molecules that signal which genes in a cell are expressed and which are silenced. According to certain animal research, when changes in markers occur in cells that mature into eggs or sperm, these changes may be passed on and displayed in the animal's progeny. Further study may show if chronic stress has comparable consequences in people, and whether inheriting suppressed or active genes contributes to family histories of cancer, obesity, cardiovascular, psychiatric, or neurodevelopmental disorders.