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's not known exactly how LSD affects the brain. Scientists believe it has to do with serotonin. Serotonin is a brain chemical that carries messages related to perception and behavior. LSD somehow disrupts that process, leading to a trip that can last for 12 hours or more. A person starts feeling high about 30 to 90 minutes after taking LSD. How the drug actually affects a person depends on many things, including the amount of LSD taken, the person's surroundings, and his or her personality and mood.