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 It can worsen hypoxic brain damage by damaging the lungs and also by increasing the levels of carbon monoxide in the blood. 2  Heart disease leading to congestive heart failure may also lower the amount of oxygen in the blood. 3  Sudden, severe hypoxia may also cause brain damage and symptoms of dementia.