Young children twirl around in circles until they are dizzy and then fall to the ground, laughing and feeling giddy. Moments later they jump up and do it again. A teenage boy becomes nervous and anxious as he builds up the courage to ask a girl out on his first date. After school, he races home to excitedly tell his friends about his experience. On the same day, one person wins the lottery while another loses her job. Every day, people have experiences that alter their mood and feelings. Some experiences cause subtle changes in mood, whereas other experiences cause tremendous mood changes.
Drugs of abuse can have similar effects because they produce changes in mood by stimulating or depressing natural brain chemicals called neurotransmitters. Neurotransmitters are naturally occurring chemicals in the brain that are necessary for the transmission of nerve messages in the nervous system. Some neurotransmitters cause nerve messages to travel quickly, whereas others help to slow messages down. Neurotransmitters are responsible for the normal activity of the brain, including emotions, thinking, perception, and behavior.
Consider a person being robbed at gunpoint. Because of the danger involved, it is likely that both the thief and the victim will experience an increased heart rate, shortness of breath, a trembling sensation, muscle tension, and a surge in energy. The victim might describe her feelings as anxiety and fear. In contrast, the thief may describe his feelings as excitement and power. Their interpretation of the experience is different; hut both may experience the same symptoms and signs caused by a rapid release of certain neurotransmitters.
The body tries to remain in a state of homeostasis or balance. With a healthy diet and life-style, the body may be able to keep these neurotransmitters in balance. However, severe elevations or depletions of certain.........
