It is truly amazing how the brain works and reacts to the stimuli in which people find the most pleasure. There is a part of the brain that controls the pleasure the body experiences through various actions such as sex, drugs and even eating! The brain works in more ways than you might imagine behind the scenes and this is what makes the human body such an amazing tool. But sometimes the body makes something too good and it becomes addictive. There is a reward system that controls the feeling of pleasure through stimuli that can be physical such as having sex or using drugs and mental such as thinking about a significant other. These external and internal stimuli will be described, explained and also the effects of the stimulus when activated will also be described. If one stimulus can cause so many changes in the body, then what is it? A stimulus is a change in the internal and external environment detected by the body. The stimulus triggers the brain to release dopamine to give us pleasant rewards when we engage in behavior that people find pleasant. Our ability to “feel good” involves brain neurotransmitters in this reward system. This reward system is made up of neurons that release dopamine in areas of the brain called the ventral tegmental area (VTA), nucleus accumbens, and amygdala. The VTA dopaminergic system is strongly associated with the brain's reward system. Dopamine is released in areas such as the nucleus accumbens and prefrontal cortex as a result of rewarding experiences such as food, sex and neutral stimuli that are associated with them. The source of this dopamine comes primarily from the VTA, although the substantia nigra may also contribute. Electrical stimulation of... the center of the paper... for an extended period of time. This sensation is followed by an increase in heart rate, blood pressure and sexual appetite. Dopamine uptake continues to be blocked by constant cocaine use as the system releases less and less dopamine and the reward system dries up. The cocaine user becomes anxious and unable to experience pleasure without the drug. As a result, postsynaptic cells become hypersensitive and develop new receptors in a desperate attempt to pick up dopamine signals. A vicious cycle of addiction begins and cocaine is necessary to feel pleasure as it further suppresses the release of dopamine. Dopamine alone is not enough to maintain the addiction, to maintain the addiction you need glutamate, which plays an important role in learning. Glutamate signaling appears to cause more permanent changes in the brain that lead to drug-seeking behaviors elicited by users.