Homeostasis

Walter Bradford Cannon is credited with coining the term homeostasis to refer to the processes that maintain a constant internal body environment. For homeostasis to work, there must be feedback systems that various physiological functions turn off and on. Imagine a feedback system like the thermostat in your furnace or air conditioning system. If the temperature increases above the set point determined by the system, then the thermostat shuts off the furnace. In this way the temperature is kept at a desired steady state. If the temperature decreases below the set point determined by the system, then the thermostat turns on the furnace to maintain a desired steady state. A feedback system revolves around a cycle of events. Information about a change is fed back to the system so that the regulator (in this example the thermostat) can control the process (in the above example of temperature regulation).

A good example of homeostasis in the body is the method by which the body maintains a constant temperature of 98.6 degrees Fahrenheit. If physical exertion or external heat causes the body temperature to rise, the brain sends a signal to increase the rate of sweating. Heat is carried away in the evaporating sweat. If body temperature begins to drop due to a cold external environment, shivering begins to generate heat and keep the body temperature at that critical 98.6 degrees F. Other metabolic functions under homeostatic control include: Hormone production and concentration level maintenance. Maintenance of serum oxygen levels and carbon dioxide levels. pH balance in the blood and cells. Water content of cells and blood. Blood glucose levels, and other nutrient levels in the cell. Metabolic rate.

Figure 1-1:Homeostasis example

The concept of homeostasis is of special interest to the fitness enthusiast. You are in equilibrium with the environmental stimuli imposed upon you. Think for example, how your muscles change in response to different training programs. If you spend most of your time lifting heavy weights, your muscles will grow larger. A shift in your homeostasis has taken place. The simple action of weight lifting causes more protein synthesis in the muscles being exercised with weights. Hormone levels change to accommodate this growth. On the other hand, if you choose to run several miles per day, your muscles will take a different form: develop a higher endurance capacity, stimulate the formation of more fat burning slow twitch muscle fibers, and develop a higher capacity to use oxygen in energy production. Nutrient intake is an important factor, which can affect your homeostatic balance as well. Eating too much of the wrong foods, or too little of the right foods can cause homeostasis to shift. Too much fat and calories, and your body stores fat. Not enough protein, and your muscles break down. Not enough carbohydrates, and you will feel tired sooner. For optimum homeostasis and metabolism, eating the right nutrients in the right amounts at the right times is vital.