| I: | A chemosensitive area is situated adjacent to the rhythm centre which is highly sensitive to CO2 and hydrogen ions. |
| II: | Receptors associated with aortic arch and carotid artery can recognise changes in O2 concentration and send necessary signals to the rhythm centre for remedial actions. |
| III: | The role of oxygen in the regulation of respiratory rhythm is most significant. |
| I: | is located in the medulla oblongata. |
| II: | regulates the duration of inhalation and increases respiratory rate. |