Acid Base Physiology

Calcium and phosphorus are co-regulated as well in the body. It involves three major

hormones: Parathyroid hormone (PTH), vitamin D3 (calcitriol), and calcitonin. They are

released in varying amounts in response to the calcium levels in the body, with phosphate

following it. PTH will bring up calcium levels and calcitonin will lower the calcium levels.

Calcitriol will increase the calcium levels through increased absorption.

ACID BASE PHYSIOLOGY

Acid-base balance in the body depends on the pH level. The pH level of a solution is the

measure of the hydrogen ion and hydroxyl ions in the system or the balance of acids and bases.

The pH scale runs from 1 to 14, with a low pH being acidic and a high pH being alkaline or basic.

The pH of the body is slightly above 7, making it very nearly neutral when it comes to acid-base

balance. To keep the body from fluctuating greatly in pH levels, there are buffering systems that

keep this from happening.

A buffer or “buffering system” represents either a week acid or a weak base that will take up

hydrogen ions or hydroxyl ions to protect the system. There are several buffering systems in

place, both inside and outside the cells, which maintain the pH of the system within a narrow

range. It takes just seconds for these buffering systems to take place so that the blood pH is

maintained. An example of this is the change in respiratory rate that can increase or decrease

the CO2 level, which is a major part of the buffering of the bloodstream.

The three major buffering systems in the body are: the bicarbonate/carbonic acid system, the

phosphate system, and protein buffers. Within the cells, proteins are the major buffers; however, in the bloodstream, it is mainly the bicarbonate/carbonic acid system.

Protein buffers are common in living systems. Proteins have both positively-charged amino

groups as well as negatively-charged carboxyl groups. This combination of positive and

negative charges adds to a buffer system, binding hydrogen and hydroxyl ions, depending on

the end being looked at. Protein buffering systems make up two-thirds of the buffering that

takes place in the bloodstream and almost all of the buffering that takes place within the cells.