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.
Quick Answer. Lack of oxygen in the brain will cause permanent brain damage in as little as four minutes. Another four to six minutes without the brain receiving blood will result in increased brain damage, coma and then death.