Most of the chemical levels and chemical reactions in the human body are in a constant state of flux. When the various components of a particular system are in a relatively constant, unchanging state, we say that the system is in equilibrium. An example of chemical equilibrium in the body that can become upset or stressed is the level of water both inside and outside of your body's cells. When the water levels are in equilibrium, we say that the cells are isotonic. But if you exercise heavily and consequently sweat a lot, your body loses water via perspiration. This causes the water level in your cells to decrease to compensate, thus the cells shrink slightly and become hypertonic. Drinking some fresh water helps replace the lost water in your body, thus putting your cells back into an isotonic state of equilibrium.
Freshman Freddie is studying late (very late) for his upcoming final and has been subsisting on ramen noodles for the past three days.
Unfortunately, ramen noodles have a very high sodium content (nearly 1000mg per serving).
This puts stress on the salt balance in Freddie's body because there are now too many Na+ ions. (Long term, this can lead to high blood pressure and other problems.)
As a consequence, his body will try to get rid of excess salt through urine and restore the normal salt balance.
Homeostasis is the body's ability to return to chemical equilibrium. When there is too much of one chemical or not enough of another, the body works to maintain homeostasis.
Your body maintains your glucose levels through this. You can increase your glucose levels by eating or your pancreas will produce a hormone known as glucagon to raise your blood sugar. Contrary, your pancreas can release insulin for glucose absorption (lower blood sugar). People with diabetes are incapable of performing this homeostasis and may require insulin injections.