Why does rising CO2, not falling O2, control breathing? Medulla vs pons centres, and asthma vs emphysema

7 answers & replies

• [+][–]Nisha Verma12thSample· 1mo ago

  The map:

  • Respiratory rhythm centre: in the medulla. This is the primary centre that sets the rhythm of breathing.
  • Pneumotaxic centre: in the pons. It moderates the rhythm centre. It can reduce the duration of inspiration, and therefore change the respiratory rate.
  • Chemosensitive area: adjacent to the rhythm centre, highly sensitive to CO2 and H+ ions. When these rise, this area signals the rhythm centre to make adjustments to remove them.
  • Aortic arch and carotid artery receptors: also detect changes in CO2 and H+ and send signals to the rhythm centre.

  So the pneumotaxic centre is in the pons and the question was wrong as stated. Medulla = rhythm, pons = moderator.

  Report
• [+][–]Kavya NaikDropperSample· 1mo ago

  About your breath-holding experiment, it's a nice observation. CO2 is carried in blood mostly as bicarbonate, and $CO_2 + H_2O \rightarrow H_2CO_3 \rightarrow H^+ + HCO_3^-$. So when CO2 builds up, H+ also rises, and the chemosensitive area picks it up. When you hold your breath, CO2 and H+ go up quickly and the centre pushes you to breathe, well before oxygen drops to a dangerous level. That's why the urge comes from the CO2 build-up. Body uses CO2 as an early, sensitive alarm for ventilation. O2 plays a minor role under normal conditions.

  Report
• [+][–]Diya Menon11thSample· 1mo ago

  ahh I remember it as the chemosensitive area being in the pons, next to the pneumotaxic centre, because "chemo" and "pneumo" both sound alike? so the rhythm centre is in the medulla and the chemo + pneumo are in the pons 😅

  Report

  • [+][–]Rahul DubeyDropperSample· 1mo ago

    Diya, the sound-alike trick leads you wrong here. The chemosensitive area is next to the rhythm centre, so it is in the medulla area. Only the pneumotaxic centre is in the pons. A better handle: rhythm and chemo are "the main control room" in the medulla; pneumotaxic is the "volume knob" in the pons.

    Report

    • [+][–]Farhan ShaikhDropperSample· 1mo agoAuthor

      got it: medulla = rhythm + chemo, pons = pneumotaxic. Writing "volume knob" in my notebook. Thanks everyone, ab mess ka khana bhi hazam ho gaya 😂

      Report
• [+][–]Mehak AroraDropperSample· 1mo ago

  The disorders in a few lines each:

  • Asthma: difficulty in breathing causing wheezing, due to inflammation of bronchi and bronchioles. It's an airway problem.
  • Emphysema: a chronic disorder where the alveolar walls are damaged, so the respiratory surface decreases. Cigarette smoking is the major cause. It's an alveoli problem.
  • Occupational respiratory disorders: in industries involving grinding or stone-breaking there's a lot of dust. Long exposure can cause inflammation leading to fibrosis (proliferation of fibrous tissue) and serious lung damage. Workers should wear protective masks.

  So airways (asthma), alveoli (emphysema), dust fibrosis (occupational).

  Report
• [+][–]Siddharth RaoDropperSample· 1mo ago

  Exam note: the options often say "oxygen concentration is the main regulator of respiratory rhythm". That is wrong. And "increase in CO2 and H+ decreases the rate" is wrong too, they raise it. I've seen both versions in test series. Remember: more CO2/H+ in blood goes to chemosensitive area, then rhythm centre, then breathing rate goes up.

  Report