● `color{violet}(CO_2)` is carried by haemoglobin as `color{brown}("carbamino-haemoglobin")` (about `20-25 %`).

● This `color{violet}("binding")` is related to the partial pressure of `color{violet}(CO_2)`.

● `color{violet}(pO_2)` is a major factor which could affect this `color{violet}("binding.")`

● When `color{violet}(pCO_2)` is high and `color{violet}(pO_2)` is low as in the `color{violet}("tissues,")` more binding of `color{violet}("carbon dioxide")` occurs whereas, when the `color{violet}(pCO_2)` is low and `color{violet}(pO_2)` is high as in the alveoli, dissociation of `color{violet}(CO_2)` from `color{violet}("carbamino-haemoglobin")` takes place, i.e., `color{violet}(CO_2)` which is bound to`color{violet}(" haemoglobin")` from the tissues is delivered at the `color{violet}("alveoli.")`

● RBCs contain a very high concentration of the enzyme, `color{brown}("carbonic anhydrase")` and minute quantities of the same is present in the `color{violet}("plasma too.")`

● This `color{violet}("enzyme facilitates")` the following reaction in both directions.

`color{violet}(CO + H_2O overset(" Carbonic anhydrase")⇄ H_2CO_3 overset("Carbonic anhydrase")⇄ HCO_3^(-) + H^(+))`

● At the `color{violet}("tissue")` site where partial pressure of `color{violet}(CO_2)` is high due to catabolism, `color{violet}(CO_2)` diffuses into blood (RBCs and plasma) and forms `color{violet}(HCO_3)` and `color{violet}(H^+)`,.

● At the `color{violet}("alveolar")` site where `color{violet}(pCO_2)` is low, the reaction proceeds in the opposite direction leading to the formation of `color{violet}(CO_2)` and `color{violet}(H_2O)`.

● Thus, `color{violet}(CO_2)` trapped as `color{brown}("bicarbonate")` at the `color{violet}("tissue level")` and transported to the `color{violet}("alveoli")` is released out as `color{violet}(CO_2)`

● Every 100 ml of `color{violet}("deoxygenated blood")` delivers approximately `color{violet}(4 ml)` of `color{violet}(CO_2)` to the `color{violet}("alveoli")`.

● Human beings have a significant ability to maintain and moderate the `color{brown}("respiratory rhythm")` to suit the demands of the `color{violet}("body tissues.")`

● This is done by the `color{violet}("neural system.")`

● A specialised centre present in the medulla region of the brain called `color{brown}("respiratory rhythm centre")` is primarily responsible for this regulation.

● Another centre present in the `color{violet}("pons region")` of the brain called `color{brown}("pneumotaxic centre")` can moderate the functions of the `color{violet}("respiratory rhythm centre.")`

● `color{violet}("Neural signal")` from this centre can reduce the duration of inspiration and thereby alter the `color{violet}("respiratory rate.")`

● A `color{brown}("chemosensitive")` area is situated adjacent to the `color{violet}("rhythm centre")` which is highly sensitive to `color{violet}(CO_2)` and `color{violet}("hydrogen ions.")`

● Increase in these substances can activate this centre, which in turn can signal the `color{violet}("rhythm centre")` to make necessary adjustments in the `color{violet}("respiratory process")` by which these substances can be eliminated.

● Receptors associated with `color{brown}("aortic arch and carotid artery")` also can recognize changes in `color{violet}(CO_2)` and `color{violet}(H^+)` concentration and send necessary signals to the rhythm centre for remedial actions.

● The role of `color{violet}("oxygen ")` in the regulation of `color{violet}("respiratory rhythm")` is quite insignificant.

`star` `color{brown}("Asthma")` is a difficulty in `color{violet}("breathing causing")` wheezing due to inflammation of `color{violet}("bronchi and bronchioles.")`

`star` `color{brown}("Emphysema")` is a `color{violet}("chronic disorder")` in which alveolar walls are damaged due to which respiratory surface is decreased.

`star` `color{green}("Occupational Respiratory Disorders:")`

● In certain industries, especially those involving `color{brown}("grinding or stone-breaking,")` so much dust is produced
that the defense mechanism of the body cannot fully cope with the situation.

● Long exposure can give rise to `color{brown}("inflammation leading to fibrosis")` (proliferation of fibrous tissues) and thus causing serious `color{violet}("lung damage.")`

● Workers in such industries should wear `color{violet}("protective masks.")`