Neurotransmitters

The adult human brain weighs about 1,400 grams and contains about 100 billion neurons (that may vary by perhaps 1,000 different types) capable of performing billions of calculations a second and has 20 to 50 times as many supportive nonneural cells called glia. The intraneural signals generated can travel at 400 meters per second. The signaling process by which a neuron excites (behaviorally promotes activity and wakeful-ness) or inhibits (behaviorally promotes calm and sleep and lessens aggression) the next neuron in the net is called neurotransmission. This event is both electrically (about a tenth of a volt) and chemically mediated primarily by neurotransmitter substances (NTs).

The way that neurons signal each other is via the release of chemicals (designed to provide a highly specific signal to ...