Homeostasis is our inner thermostat. We maintain our equilibrium -- our inner sense of balance, comfort and smooth operation -- through the act of changing our physiological processes. Healthy bodies have different responses that maintain this state both automatically and voluntarily. Some of our bodily functions, especially diseases, create a need to augment our responses with medications or treatments to maintain homeostasis.
Thermoregulation in Heat and Cold
One example of maintaining homeostasis is thermoregulation, which is regulating comfortable body temperatures in different climates. Humans find this easier than some animals, since we are endotherms -- warm-blooded animals -- possessing a consistent body temperature, as opposed to ecotherms, or cold-blooded animals. Blood temperature isn't relevant; ecotherms are externally regulated for temperature, while endotherms have internal regulators. Human response to temperature changes involves the hypothalamus, which has receptors that monitor blood temperature. Meanwhile, our skin has receptors that monitor external temperatures. Both send messages to the brain, which responds to involuntarily maintain homeostasis.
Voluntary and Involuntary
Some of the responses to temperature are voluntary: We take off our coat when it's too warm. Some are involuntary: We swelter in the heat. Our bodies generate heat in cold weather by muscular contraction -- shivering. Our skin also contracts in the cold, which reduces the heat that travels from the body core, retaining it internally, a process called vasoconstriction. Sometimes we respond as cold-blooded ecotherms do: We seek shelter, sun ourselves or move toward shade in the heat.
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Blood Glucose Homeostasis
Another response organisms display is blood glucose homeostasis. The pancreas monitors glucose concentration in our blood, and uses the hormone and enzyme glucagon, produced by alpha cells, to stimulate the breakdown of food elements into glucose, raising the level. Insulin, a second enzyme produced by beta cells, converts glucose into respiratory energy, decreasing the level in the blood. These two responses work to maintain glucose levels, although they act somewhat competitively, since the cells will not manufacture both insulin and glucagon at the same time.
Neither voluntary nor involuntary responses are sufficient if diabetes is present, since Type 1 diabetes kills off the B-cells that produce insulin. Type 2 shuts down the insulin receptors, so insulin is produced but not absorbed by the cells. In this instance, our human organism's responses are voluntary. We must modify sugar intake for Type 2 diabetes and take insulin injections for Type 1 diabetes in order to maintain homeostasis in blood glucose.