Regulation of Respiration: Respiratory Centres in the Brain
Biology · Breathing and Exchange of Gases · NEET
Breathing is controlled by three centres. The respiratory rhythm centre in the medulla is the main boss that sets the breathing rhythm. The pneumotaxic centre in the pons only moderates it (it can shorten inspiration and change the rate). A chemosensitive area near the rhythm centre senses high CO2 and H+ ions. Memory hook: Rhythm = Medulla ("main"), Pneumotaxic = Pons ("part-time helper").
The medulla's respiratory rhythm centre is the main controller; the pons pneumotaxic centre only moderates it. The chemosensitive area (medulla) plus aortic-carotid receptors detect CO2 and H+; oxygen's role is insignificant.
Your doubts, answered
Which centre is the main controller of breathing rhythm?
The respiratory rhythm centre, which is present in the medulla region of the brain. NCERT calls it 'primarily responsible' for regulation. It is the boss that keeps the normal breathing rhythm going.
Then what does the pneumotaxic centre do?
The pneumotaxic centre is in the pons region of the brain. It does NOT start breathing. It only moderates (adjusts) the rhythm centre. Its signal can reduce the duration of inspiration, and by doing this it can increase the respiratory rate. Remember: pneumotaxic = pons = part-time helper.
Where exactly is the chemosensitive area located?
It is situated adjacent to (next to) the rhythm centre, so it is in the medulla. Do not confuse it with the pneumotaxic centre in the pons. The chemosensitive area is highly sensitive to CO2 and hydrogen (H+) ions.
Does the chemosensitive area sense oxygen?
No. It senses CO2 and H+ ions, not oxygen. NCERT clearly states the role of oxygen in the regulation of respiratory rhythm is quite insignificant (negligible). When CO2 and H+ rise, this area signals the rhythm centre to speed up breathing to throw out the extra CO2.
Do the aortic arch and carotid artery play any role?
Yes. Receptors associated with the aortic arch and the carotid artery also recognise changes in CO2 and H+ concentration. They send signals to the rhythm centre for remedial action. So both the brain (chemosensitive area) and these peripheral receptors monitor CO2 and H+.
⚠️ The NEET trap ✗ Students mark that the pneumotaxic centre (pons) is the main centre that generates the breathing rhythm. ✓ The respiratory rhythm centre in the MEDULLA is primarily responsible. The pneumotaxic centre in the PONS only moderates it and can reduce the duration of inspiration. 🧠 Medulla makes the rhythm; Pons only polishes it. If a question says 'primarily responsible' the answer is the medulla's rhythm centre.
Solved Breathing and Exchange of Gases NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
What are the two respiratory centres in the brain according to NCERT?
The respiratory rhythm centre in the medulla and the pneumotaxic centre in the pons. A chemosensitive area also lies adjacent to the rhythm centre in the medulla.
Is the chemosensitive area in the medulla or the pons?
In the medulla, adjacent to the respiratory rhythm centre. The pneumotaxic centre is the one in the pons.
Why is oxygen not important in regulating breathing rate?
NCERT states the role of oxygen in the regulation of respiratory rhythm is quite insignificant. Breathing rate is mainly adjusted by CO2 and H+ ion levels, not by O2.
How does the pneumotaxic centre change the breathing rate?
By sending a neural signal that reduces the duration of inspiration. Shorter inspiration means more breaths per minute, so the respiratory rate can increase.
