Our cells are happiest when they are in their normal or “home” state. This is a state in which the temperature, the concentrations of molecules, and molecules being produced are all at the levels at which they normally function. This “normal” or “home” state is called homeostasis.
Our cells—and the tissues and organs they constitute—work hard to maintain homeostasis. We can see this in action. When it is cold out and we shiver, that’s our body trying to get the temperature up to normal levels. When it’s hot out and we sweat, that’s our body trying to get the temperature down to normal levels. We see our body trying to maintain homeostasis when we feel hungry, or thirsty. Homeostasis is an important characteristic of living things. If you were in the desert, your body would be working hard to maintain homeostasis—despite the high temperature and the lack of water.
There are many different types of cells in the body, but all of them work to maintain homeostasis. For example, there are specific muscle cells for muscles, specific heart cells for the heart, specific pancreas cells for the pancreas, and skin cell cells making up the skin. The different cell types differ in how they function. They all work together to make sure the body functions normally.
A tissue is composed of specific cells performing the same function. An organ is made up of two or more types of tissues working together. Organs which work together form organ systems. Organ systems work together to maintain homeostasis.
So, how many types of tissues are there? There are four main types of tissue. Tissues are groups of cells which together form specific functions. These types are: epithelial tissue, nervous tissue, muscle tissue, and connective tissue. Epithelial tissue is found in tightly packed surface layers; such as the skin, as well as the lining of the digestive system and the lining of the mouth and nose. Nervous tissue is responsible for relaying information. All together the nervous tissues form the nervous system. The nervous system includes the sensory nerves in the body, nerves in the spinal cord, and the brain.
There are three types of muscle tissue; smooth muscle, skeletal muscle, and cardiac muscle. All three cell types have filaments which change the size. Bone, cartilage, and tendon tissues are examples of connective tissue. Connective tissue connects one part of the body to another and is involved in structural support.
The low blood temperature sends a message to the brain which then sends a message to the adrenal gland, which increases the blood temperature by raising the metabolism. The raised blood temperature then signals to the brain that it’s time to stop sending the message to the adrenal gland. A key way organ systems maintain homeostasis is via a negative feedback loop.
A negative feedback loop simply means that the result is a signal to stop. For example, if you haven’t eaten for a while your body will sense that your blood sugar is low. The low blood sugar acts as a signal for the body to start releasing sugar into your blood. However, once the blood sugar levels are back to normal—homeostasis has been reestablished—that normalcy acts as a signal for the body to stop releasing sugar into your blood.
Many problems can occur if these negative feedback loops do not function properly. For example, diabetes is a disease which results from the blood sugar negative feedback loop functioning abnormally.