Breathing and Exchange of Gases Test -5

Respiration is a physiological process. Total lung capacity (TLC) includes vital capacity (VC) and residual volume. Cutaneous respiration is the breathing via skin.

20 – 25% of CO₂ is transported to the alveoli as carbamino-haemoglobin.

In tissues, low pO₂, high pCO₂, high H⁺ concentration and higher temperature exist,the conditions are favourable for dissociation of oxygen from the oxyhaemoglobin.

The solubility of carbon dioxide is 20-25 times higher than that of oxygen, the amount of carbon dioxide that can diffuse through the diffusion membrane per unit difference in partial pressure is much higher compared to that of oxygen.

CO₂ is carried by haemoglobin as carbamino-haemoglobin. This binding is related to the partial pressure of CO₂.pO₂ is a major factor which could affect this binding.

An enzyme present in red blood cells, carbonic anhydrase, aids in the conversion of carbon dioxide to carbonic acid and bicarbonate ions. When red blood cells reach the lungs, the same enzyme helps to convert the bicarbonate ions back to carbon dioxide, which we breathe out. It transportes nearly 70% of carbondioxide as bicarbonate.

A specialised centre present in the medulla region of the brain called respiratory rhythm centre is primarily responsible for this regulation. In the pons region of the brain called pneumotaxic centre can moderate the functions of the respiratory rhythm centre.

In central nervous system, regulation of respiratory rhythm during normal breathing is dependent upon concentration of carbon dioxide gas in air.

The pneumotaxic centre can moderate the functions of the respiratory rhythm centre. Neural signal from this centre can reduce the duration of inspiration and thereby alter the respiratory rate.