The human body is well adapted to deal with short-term stress, but if it remains on orange alert for an extended period of time, you can grow vulnerable to some serious health problems. Here's how major systems respond to your worries.

• Nervous

  The "fight or flight" response begins here: When you're stressed, the brain's sympathetic nerves signal the adrenal glands to release a chemical variety pack. Persistently high levels may impair memory, learning, and up your odds for depression.

• Endocrine

  Stress hormones trigger the liver to produce more blood sugar, to give you that kick of energy in the moment of perceived danger. But if the "danger" you're concerned with is a long-term dilemma and you're already at risk for type 2 diabetes, bad news: Elevated glucose levels may turn you into a card-carrying diabetic.

• Respiratory

  At high-stress moments, you may find yourself breathing faster, feeling short of breath, or even hyperventilating. Over the long term, this strain on the system can make you more susceptible to upper-respiratory infections.

• Reproductive

  Stress can lengthen or shorten your menstrual cycle, stop it altogether, or make your periods more painful. During pregnancy you should consider participating in a controlled activity like prenatal yoga.

• Immune

  Short-term stress can actually boost the immune system, helping your body fight infection. Ongoing stress, however, turns things in the other direction, possibly slowing wound healing, leaving you more susceptible to infection, and worsening skin conditions such as eczema and yes — acne.

• Digestive

  Extreme stress can cause dry mouth, indigestion, nausea, and gas, and it stimulates the muscles of the intestines, possibly causing diarrhea or constipation. Having these symptoms chronically, you may increase your risk for irritable bowel syndrome, severe heartburn, and ulcers.

• Musculoskeletal

  Muscles tense to deal with what your body perceives as danger. Constantly tight muscles can cause headaches and neck, shoulder, and back pain. Chronic stress may also increase your likelihood of developing osteoporosis.