ANATOMY

Detailed explanation-1: -As will be explained in more detail later, increased carbon dioxide levels lead to increased levels of hydrogen ions, decreasing pH. The increase in hydrogen ions in the brain triggers the central chemoreceptors to stimulate the respiratory centers to initiate contraction of the diaphragm and intercostal muscles.

Detailed explanation-2: -Carbon dioxide influences the pH of blood by reacting with water to form carbonic acid (H2CO3), which can dissociate to form a hydrogen ion (H+) and a hydrogen carbonate ion (HCO3-). Increasing the concentration of carbon dioxide in the blood therefore results in more H+ ions and a lower pH.

Detailed explanation-3: -Pressure of carbon dioxide in the blood. CO2 is an acid managed by the lungs. As PaCO2 increases, the blood becomes more acidic and the pH decreases. As PaCO2 decreases, the blood becomes less acidic and the pH increases.

Detailed explanation-4: -The increase in CO2 concentration in the blood increases the rate of breathing. This increase in CO2 brings about a good change in the pH of the blood. This change could be detected by chemoreceptors of the medulla oblongata of the hindbrain which is also a regulatory centre for respiration.

Detailed explanation-5: -The increase in pH is often caused by hyperventilation (excessively deep breathing). When a person hyperventilates they exhale more carbon dioxide than normal. As a result the carbon dioxide concentration in the blood is reduced and the bicarbonate/carbonic acid equilibrium shifts to the left.