Understanding the natural stress response

Chronic stress can harm your body and mind by releasing stress hormones for too long. This can lead to issues such as headaches, poor sleep and heart disease. It also can weaken your immune system. And it can lead to changes in daily habits, such as getting less physical activity. This can make it harder for your body to stay healthy and recover from illness.

When you face a perceived threat, a tiny area at the brain's base, called the hypothalamus, sets off an alarm system in the body. An example of a perceived threat is a large dog barking at you during your morning walk. Through nerve and hormonal signals, this alarm system prompts the adrenal glands, found atop the kidneys, to release a surge of hormones, such as adrenaline and cortisol.

Adrenaline makes the heart beat faster, causes blood pressure to go up and gives you more energy. Cortisol, the main stress hormone, increases sugar, also called glucose, in the blood. It also helps the brain use glucose more effectively. It also increases the availability of substances in the body that repair tissues.

Cortisol also slows body functions that are not needed or harmful in a fight-or-flight situation. It changes immune system responses and makes it harder for the digestive system, the reproductive system and growth processes to work. This complex natural alarm system also communicates with the brain regions that control mood, motivation and fear.