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.
In general, the brain can withstand up to three to six minutes without oxygen before brain damage occurs, but this may vary from person to person.If the brain goes without oxygen longer than this, serious and often irreversible damage is likely to take place.eath is usually declared once the brain has gone more than 15 minutes without oxygen. Although the brain can only go a few minutes without oxygen before some type of brain damage occurs, patients can often regain cognitive function if treated quickly.