How does anesthesia induce unconsciousness?

Great question: The actual mechanism that cause loss of consciousness has yet to be worked out. We know some of the neuro reception involved and we know that membrane permeability of brain cells plays a role. But there are 5 or more completely differ medications that cause general anesthesia and they all have different pharmacologist actions. Go figure.....

Unknown: There are many theories that are beyond the scope of this answer. But in reality no one knows. It is theorized that through protein interactions in the cerebral cortex the normally tonic oscillation of brain wave are converted to slow waves.

Gas : When you under to anesthesia you get a number intravenous medications and you are breathing anesthetic gases which keeps you asleep or unconscious.

No one quite knows.: The anesthetic agents and gasses that have been used to induce over the anesthetic act in the central nervous system. There are several theories about what they actually do, but most boil down to putting certain areas of cells to sleep that then cause the patient to fall asleep.