The body has the ability to physiologically regulate its internal environment with response to fluctuations that occur in the internal or external environment through homeostasis. Homeostasis refers to a state of constant equilibrium within the cells, tissues, organs, and fluids of the body. The body requires a stable, constant internal environment for the many processes that occur to keep the organism functioning. For example, animals need a balance of ions circulating in their blood systems to prevent blood pH values from increasing or decreasing.
The mechanical operation of a thermostat can be considered analogous to the body's own temperature regulation. The thermostat responds to temperature changes in the room by signaling the air conditioner (or heater) to either turn on or off. The temperature of the home is maintained within a narrow range by this system. Biological systems are more complex, but the mechanisms maintaining internal temperature within a narrow range are similar. Internal temperature regulation is one facet of homeostasis.
The process of maintaining homeostasis is complex. It has an effect on the function of multiple body systems and several organs play a role in maintaining homeostasis. These include the liver, kidneys, and brain. Specifically, the liver works to maintain the metabolic processing of carbohydrates and toxic substances constantly entering the body from the external environment. The kidneys function to maintain blood fluid volume and acid levels in the blood. The brain regulates homeostasis through the hypothalamus region of the brain and the glands of the endocrine system. Homeostatic disruption can occur when the body systems are unable to maintain balance. This inability to maintain balance, also referred to as homeostatic imbalance, will affect normal functions in the body, leading to a disease, disorder, or even death. One common example is hypothyroidism in which the body fails to produce or regulate thyroid hormones properly. The result of failed thyroid hormone homeostasis includes weight gain, lack of concentration, and fatigue. Diabetes is another condition resulting in homeostatic imbalance. People with diabetes have pancreas glands that do not produce sufficient quantities of insulin, a hormone required for the homeostatic control of blood glucose levels.
Understanding the Homeostatic Process
Homeostatic imbalances can occur due to the inability of the body to respond to a stimulus. There are two basic ways this type of imbalance occurs—deficiency or toxicity. Deficiency occurs because normal operational pathways in the body are blocked, causing an inadequate quantity of vitamins or minerals to be available to cells for use. Toxicity occurs when excess ions are present in the bloodstream, creating poisonous conditions for the cell. In both cases, whether a deficiency or toxicity, cells are affected. For example, high levels of uric acid (normally excreted by kidneys) can result in a disease called hyperuricemia.