How We Breathe: Regulation & Problems 😊
✨ How CO₂ Travels in Our Blood
- Red blood cells (RBCs) carry lots of carbonic anhydrase enzyme (a little is in plasma too). This enzyme helps CO₂ and water turn into other chemicals, and back again! 🔄
- Here’s the magic reaction it controls:\[\text{CO}_2 + \text{H}_2\text{O} \xrightarrow{\text{Carbonic anhydrase}} \text{H}_2\text{CO}_3 \xrightarrow{\text{Carbonic anhydrase}} \text{HCO}_3^- + \text{H}^+\]
- In tissues (where CO₂ is high):
- CO₂ enters blood → becomes bicarbonate (HCO₃⁻) and H⁺ ions.
- In lungs (where CO₂ is low):
- Reaction reverses → releases CO₂ to breathe out! 💨
- Fun fact: Every 100 ml of blood dropping off O₂ picks up ~4 ml of CO₂ to deliver to the lungs!
🧠 How Our Brain Controls Breathing (Regulation)
- A special spot in the brainstem (medulla) called the respiratory rhythm centre sets your breathing pace. 🎵
- Another area in the pons (the pneumotaxic centre) fine-tunes this rhythm:
- It can shorten inhales → make you breathe faster! ⏩
- Right next door, a chemo-sensitive area acts like a CO₂/H⁺ “alarm”:
- If CO₂ or H⁺ increases (e.g., during exercise), this area tells the rhythm centre: “Breathe faster to clear it out!” 🚨
- Extra sensors in the aorta + carotid artery also detect CO₂/H⁺ changes → alert the rhythm centre.
- Note: Oxygen levels play a very minor role here.
⚠️ Common Breathing Problems (Disorders)
- Asthma:
- Bronchi/bronchioles get inflamed and narrow → wheezing and trouble breathing. 🌪️
- Emphysema:
- Chronic damage to alveolar walls → shrinks the lung’s “breathing surface.” 📉
- #1 Cause: Cigarette smoking! 🚭
🔑 Must-Knows for NEET
- Carbonic anhydrase drives CO₂ ⇄ HCO₃⁻ conversion in RBCs (remember the reaction!).
- Breathing rhythm is set by the medulla’s respiratory centre, adjusted by the pons’ pneumotaxic centre.
- CO₂ and H⁺ ions (not O₂!) are the main triggers to increase breathing rate (via chemosensitive area/receptors).
- Asthma = inflamed airways; Emphysema = alveolar damage (often from smoking).
