By now, most of us will have set a new year’s resolution. Maybe you wanted to cut down on chocolate. Or lose some weight. Whatever it is, your resolution is probably what you want to change about yourself. However, your body does not like change. It likes to regulate things and keep them that way. So if you are under pressure to make a change, just give one sarcastic answer: “I can’t because of homeostasis”.
Homeostasis is described as the tendency towards a relatively stable equilibrium between interdependent elements. The body likes to control certain conditions. These include water content, body temperature and blood glucose concentration. Let’s break these down.
The body likes to stay around 37°C. This is because human enzymes work best at this temperature. (Enzymes are biological catalysts, they start different reactions within the body). The thermoregulatory center of the brain is what controls the body’s temperature. Information about how hot or cold you are is gathered from receptors in the brain and in the skin. There are many different ways your body regulates heat.
If you are too hot:
- Sweating: sweat helps to cool down the body. We lose water through sweating so we have to replace it by eating and drinking. Ions are also lost when sweating. The sweat evaporates to remove heat energy from the skin.
- Widened Vessels: blood vessels leading to the skin capillaries become wider. This allows more blood to flow through the skin, meaning more heat loss.
- Hairs Flatten: muscles in the skin quickly lay the hairs flat on our body so that they do not keep the warm in.
If you are too cold:
- Shivering: this is the result of our muscles contracting rapidly. The contractions mean that heat is released.
- Narrowed Vessels: the vessels leading to the capillaries become narrower (constricting) meaning that less blood flows through the skin. This conserves the heat.
- Hairs Stand Up: when the muscle pulls on the hairs, they stand up. These stood-up hairs trap in the heat and blood flow in the capillaries also decreases.
Water enters the body in two ways: food/drink and also it is a product of aerobic respiration in cells. Cells may become damaged or destroyed if the amount of water in the body is wrong. This is what happens if there is too much or too little water:
Too Little: The hypothalamus in the brain detects that there is not enough water in the blood. The pituitary gland then releases ADH (a hormone that tells the kidneys how much water to conserve). After it is released, the kidneys maintain the water level. This results in urine that is more concentrated – not as much water is lost.
Too Much: The hypothalamus in the brain detects that there is too much water in the blood. The pituitary gland then releases less ADH, and the kidneys reduce blood water level. This results in urine being more diluted, and more water is taken out of the body.
Glucose in the blood is controlled by the pancreas. The pancreas produces insulin, a hormone, which causes glucose to move from the blood into the cells. After eating a meal high in carbohydrates, insulin will lower the blood glucose concentration. However, some people cannot control glucose in the blood properly. Diabetes Type 1 is when the person cannot produce enough insulin, resulting in high levels of glucose in the blood. Type 2 is when the person does not produce any insulin at all – which can be even more fatal than the first type.
Altogether, our body doesn’t always like change. Homeostasis is what keeps us alive. It is what helps us to work, to play, to socialize. Without it, we probably would be dead. It just goes to show that our body is amazing. It is a brilliant machine that keeps on ticking perfectly.