Cholesterol is carried by different transport proteins classed according to their densities. High density(HDL)is good; low (LDL)is bad. More >
The Response to StressWhat do we mean when we say we are "stressed out"? We may just be having a bad day, or feeling pressured by too many things to do and too little time to do them. Or we may have had a fight with a friend or family member. Or our job may be getting to us - feeling that it is just a rat race without a purpose, or feeling too much pressure and a lack of support and camaraderie. In any case, we are "bummed out" and "frazzled" and tend to think about how we feel at the moment and how to make it better right away. Rarely do we give much thought to the longer time frame and how our body is handling or not handling the pressure. Yet, it is the longer time frame of months and even years that is important for understanding the bad side of stress.
Stress activates adaptive responses. The body marshals its forces to confront a threat and, generally, does a good job of protecting us in the short run. So why can stress also be so bad for our bodies and brains?
Stress can prematurely age us and leave us chronically fatigued or depressed. When exposure to stress — whether from a traumatic event to just the daily hassle of rush hour traffic or too much email — disrupts the body's internal balance ("homeostasis"), it can go one of three general ways: the body can regain its normal equilibrium once the stress has passed or it can become stuck in an over- or under-aroused state. How a person copes with stress — by reaching for a beer or cigarette as opposed to heading to the gym — also plays a big role in the impact stress will have on our bodies.
How the Body Handles Acute StressWhen the body is challenged by almost anything that happens to us, from getting out of bed in the morning or running up a flight of stairs or having to stand up and give a talk, the brain activates the autonomic nervous system (ANS), the involuntary system of nerves which controls and stimulates the output of two hormones, cortisol from the adrenal cortex and adrenalin from the adrenal medulla. These two hormones and the activity of the ANS help us cope: the ANS and the adrenalin keep us alert by increasing our heart rate and blood pressure and quickly mobilizing energy reserves. In contrast, cortisol works more slowly, helps replenish energy supplies and, at the same time, helps us to remember important things. For example, cortisol readies our immune system to handle any threat — bacterial/viral or injury.
Another aspect of cortisol action is called "containment." Many physiological systems are pitted against one another so that neither system can get out of control. The initial, first line response to many noxious or pathogenic agents is normally "contained" by circulating levels of cortisol. This is why we take corticoids for an inflammation or skin irritation. Cortisol also contains acquired immune responses, and this is particularly useful when those responses are harmful, such as in an allergy or an autoimmune disorder.
All of these adaptive responses are described by the term "allostasis" which means "maintaining stability, or homeostasis, through change."1 The body actively copes with a challenge by expending energy and attempting to put things right. Most of the time it succeeds but the real problems arise when the systems involved in allostasis don't shut off when not needed or don't become active when they are needed.
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