How Stress Takes Its Toll

By Michael Lemonick

ACUTE A response to imminent danger, it turbocharges the system with powerful hormones that can damage the cardiovascular system

CHRONIC Caused by constant emotional pressure the victim can't control, it produces hormones that can weaken the immune system and damage bones

1 A stress response starts in the brain...

When the brain detects a threat, a number of structures, including the hypothalamus, amygdala and pituitary gland, go on alert: they exchange information with each other and then send signaling hormones and nerve impulses to the rest of the body to prepare for fight or flight

2 ...and the body unleashes a flood of hormones...

Adrenal glands react to the alert by releasing epinephrine (adrenaline), which makes the heart pump faster and the lungs work harder to flood the body with oxygen

The adrenal glands also release extra cortisol and other glucocorticoids, which help the body convert sugars into energy

Nerve cells release norepinephrine, which tenses the muscles and sharpens the senses to prepare for action. Digestion shuts down

3 ...that can cause significant damage

When the threat passes, epinephrine and norepinephrine levels drop, but if danger comes too often they can damage the arteries. Chronic lowlevel stress keeps the glucocorticoids in circulation, leading to a weakened immune system, loss of bone mass, suppression of the reproductive system and memory problems