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.
12 to 15 minutes - irreverseable brain damage intensifies and to heart as well. 15 to 20 minutes - brain damage reaches point to cease brain wave function - death. These times are estimates and can vary based on many factors however the total amount of time to death will not vary by much. Once the oxygen is depleted in the human system, biological death will occur in about 20 minutes. Hope this answers the question.