Poetry, song, and folklore have long portrayed the heart as the province of the emotions, while making rational thought the business of the brain. Actually such emotions as fear, love, hate, anger, elation, greed, lust, envy, and shame have not one cause or source but several, beginning with the internal or external event that provokes them. Although emotions often involve a quicker heartbeat and other "heartfelt" effects, the heart is just one part of a complex story.
Each conscious emotion is the result of a welter of signals traveling back and forth on nerve and brain pathways. If there is any one control center for all this activity, it is the limbic system, the collective name (from Latin limbus, meaning "border") for several interconnected structures that lie near the brain's core. Enveloping the top of the brain stem, they form a borderland between the "lower" or "animal" parts of the brain (mainly involved with instincts, drives, and automatic regulation of body processes) and the higher, uniquely human brain areas, associated with the cerebral cortex, which permit advanced reasoning and planning. In this strategic spot, a kind of crossroads where visceral feelings, cognition, and memory meet, the limbic system helps shape the basic motivations and emotions of our lives.