You stop sprinting — but you keep puffing hard for a whole minute afterwards. Why doesn't it switch off straight away?
Tap to reveal
During the sprint your muscles ran short of oxygen and built up extra carbon dioxide and waste — an “oxygen debt”. Even at rest, your respiratory and circulatory systems keep running hot to deliver the catch-up oxygen and clear that backlog. Once the debt's repaid, your rates drop back to normal.
You stand up too fast and feel faint for a second. Which system lagged, and which cells noticed?
Tap to reveal
For a moment the circulatory system can't push enough blood up to your brain cells against gravity. Those brain cells briefly run short of oxygen, so you feel light-headed — until the heart and vessels adjust and supply catches up. It's a delivery lag, not a brain fault.
Someone's airway gets blocked. Their heart is still beating strongly — so why are their cells still in trouble?
Tap to reveal
The circulatory system is fine, but the respiratory system can no longer load oxygen into the blood. So the heart is pumping blood that carries no fresh oxygen — a working courier with an empty parcel. With no oxygen store to fall back on, cells starve within minutes. One broken link breaks the whole chain.