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.
It can last from several seconds to several minutes, and it's completely terrifying. Essentially, it's the opposite of what happens with hypnagogic jerks, where your brain wakes up before the paralysis that accompanies deep sleep goes away, Dr. Winter says. You may feel like you can't breathe. Many people describe it as an elephant sitting on their chest.