Homeostasis is defined as the tendency of the body to
maintain a constant internal environment. The body manages itself by using
feedback loops that
make adjustments to different variables such as blood calcium levels, blood glucose levels, and metabolism. Without these feedback loops our bodies would not be able to function as there would be no balance.
Blood Calcium Levels:
This feedback loop monitors our blood calcium levels. When there is too much calcium in our blood our
Thyroid is alerted and releases
calcitonin. Calcitonin is in charge of lowering our blood calcium level by reducing calcium uptake in the kidneys and depositing calcium in our bones. Doing so removes excess calcium from our blood and stores them away, hereby lowering our blood calcium levels to the norm.
On the other hand, sometimes our blood calcium level is too low. When this occurs, our body is required to increase these levels by stimulating the
Parathyroid to release
PTH or
Parathyroid Hormone. PTH signals the bones the start releasing calcium, the kidneys and intestines to increase uptake of calcium through Vitamin D. Eventually our blood calcium level will increase to an acceptable level.
Blood Glucose Levels:
Here is another feedback loop that helps sustain our body's blood glucose levels. When we have too much sugar in our body the
Beta cells in our pancreas releases
insulin. The insulin stimulates our body cells to take up more glucose and our liver to store the excess as glycogen. As glucose is removed from our blood stream our blood glucose levels decrease to normal and the release of insulin diminishes.
When our blood glucose level is too low the
alpha cells in our pancreas release
glucagon. Glucagon tells the liver to break down glycogen and release the glucose into the blood stream. Afterwards, blood glucose levels start to increase to a set point and the release of glucagon diminishes.
Metabolism:
Our metabolism controls the nutrients and energy in our body. When our metabolism is working too much,
Triiodothyronine (T3) and
Thyroxine (T4) signal the hypothalamus and pituitary gland to stop producing
TSH which, therefore, stops the production of T3 and T4. This brings our metabolism back into balance.
However, when our metabolism is too low, our
hypothalamus stimulates the release of
TSH which tells the thyroid to start releasing
T3 and T4. This affects the heart, liver, bones, and central nervous system activity. Our body will start to sweat and our heart rate will increase, thus restoring our metabolism to its norm.
