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.
There is debate over the dangers of choke-outs. After 4 to 6 minutes of sustained cerebral anoxia, permanent brain damage will begin to occur, but the long-term effects of a controlled choke-out for less than 4 minutes (as most are applied for mere seconds and released when unconsciousness is achieved) are disputed.