Concepts of Lifetime Fitness

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Concepts of Lifetime Fitness

September 1, 1997

Homeostasis is the state of equilibrium in which the internal environment of the human body remains relatively constant.  Two excellent examples of homeostasis are how the body maintains a constant temperature and blood pressure during strenuous physical activity or exercise.  Although there are many other activities in the body that display homeostasis, I will only discuss these two.   Temperature in the human body is usually kept at approximately 37 degrees Celsius.  To maintain such a strict temperature, the body has a few functions to combat the outside elements.  People cannot make themselves cold as readily as make themselves hot, however I will mention both homeostasis functions.  When the external temperature decreases, a portion of the brain called the hypothalamus detects the drop by means of the blood.  To compensate, the brain sends chemical and electrical impulses to the muscles.  These impulses tell the muscles to begin to contract and relax at very high intervals.  This is commonly known as shivering.  The production of Adenosine Triphosphate or ATP in the mitochondria of the muscles produces heat.  If the body temperature does not rise immediately after this, then a second function begins. The brain will signal the blood vessels near the skin to constrict or narrow in diameter.  This occurs so the heat deep in the muscles is conserved.  Since the vessels are now smaller in diameter, less blood is needed to fill them.  Since less blood is needed through the vessels, the heart begins to slow.  If the body remains in this slowed state, hypothermia could result.  Hypothermia is the condition in which metabolic processes are inhibited.  The medical world has taken advantage of this by inducing hypothermia in patients that are undergoing organ transplants.

To fight temperatures higher than normal, as in exercise or on hot days, the body reacts in the opposite way than with cold.  Again, the...
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