Читать книгу The Mind-Body Cure - Bal Pawa - Страница 38

Our brain is busy and promotes efficiency. Therefore, when it comes to stress, the brain consolidates, simplifies, and anticipates any remote memory of fear or threat. The primary system for regulating the effects of stress on the body is the hypothalamic-pituitary-adrenal (HPA) axis (Figure 2.3). When the limbic system sends a message of fear or threat to the hypothalamus, it releases a hormone called corticotropin-releasing factor (CRF) in reaction to the stress. This CRF stimulates the pituitary gland, which then releases adrenocorticotropic hormone (ACTH), and in turn ACTH stimulates the adrenal glands to release cortisol.

Cortisol is just one of the hormones produced by the adrenal glands. These triangular glands, which sit atop the kidneys, have two parts: an outer part called the adrenal cortex and an inner part called the adrenal medulla. The outer part produces hormones that are essential to life; for example, cortisol, which regulates metabolism and helps your body achieve homeostasis, as well as aldosterone, which helps to regulate blood pressure. The inner part of the gland produces the body’s nonessential hormones, including adrenaline, which helps the body adapt to stress. Too much (or too little) of any of these hormones is not a good thing, but too much of the essential stress hormone cortisol can be especially damaging, because it causes a cascade of detrimental effects throughout the body.

When overt and/or covert stress acts on the brain, the autonomic nervous system's sympathetic ("gas") or parasympathetic ("brakes") divisions are affected. Activating the sympathetic nervous system changes the body's concentration of adrenaline and cortisol, which are hormones produced by the adrenal glands above the kidneys. When stress acts on the brain, the hypothalamus and pituitary gland direct the adrenal glands to increase adrenaline and cortisol production.

Figure 2.3. How the brain communicates stress to the body