What is the physiological importance of buffers? If there is such a buffer in the blood, what happens if the pH of the blood suddenly goes down? Suddenly goes up?

Buffers are the solution that is used to maintain the pH of the solution. It resists the change in the pH. Since, many of the chemical reactions are very specific to pH and temperature so it is very important to maintain the pH of the solution.

The bicarbonate ions and hydroxide ions serves as natural buffers in the blood. If the pH of the blood goes down below the normal then bicarbonate ions are released to maintain the pH of the blood.

If the p of the blood goes more than normal then the hydroxide ions acts as a buffer and maintains the pH of the blood.