In those cases, the spread between the bid & ask goes to the market maker as compensation for making a market in a stock. For a liquid stock that is easy for the market maker to turn around and buy/sell to somebody else, the spread is small (narrow).
In cerebral hypoxia, sometimes only the oxygen supply is interrupted. Brain cells are extremely sensitive to a lack of oxygen. Some brain cells start dying less than 5 minutes after their oxygen supply disappears. As a result, brain hypoxia can rapidly cause severe brain damage or death.
1 Anoxic brain injuries are caused by a complete lack of oxygen being provided to the brain, which results in the death of brain cells after approximately four minutes of oxygen deprivation.  Hypoxic brain injuries are brain injuries that form due to a restriction on the oxygen being supplied to the brain.