Drugs affect the brain and, in turn, can alter mood and behavior. Drugs are chemicals that enter our brain's communication system and disrupt the way nerve cells receive, send, and process information. Drugs interfere with the exchange of information in the brain, producing changes that promote repeated drug use. Drugs can mimic the brain's natural chemical messengers or overstimulate our brain's reward circuitry. The brain gets used to the chemical changes caused by the chemical changes caused by the substance. It begins to alter its normal production and begins to release neurotransmitters. The user begins to lose control and has difficulty limiting medication intake; the urge to consume the substance becomes more compulsive because it has affected the region of the brain that controls impulses, behavior and desire. Repeated drug use over time changes the structure of the brain and its functions in fundamental and long-lasting ways. For example, in marijuana or heroin, they have a similar structure to chemical messengers called neurotransmitters (produced naturally by the brain). So, because of this similarity, the drugs are able to trick brain receptors and active nerve cells to send abnormal messages. When using a drug like cocaine, nerve cells release an abnormal amount of natural neurotransmitters and it also prevents the normal recycling of neurons. brain chemicals needed to interrupt the signal between neurons. This disruption produces an amplified message that disrupts normal communication patterns in the brain.4. Explain how altered neurotransmission causes some people to become dependent on chemicals.6. It explains what addiction is and explains why there is no one to define the amount of dopamine receptors available, which in return decreases the functions of the reward circuit. They are forced to abuse drugs to bring their dopamine function back to normal, which requires a larger amount to reach the normal level of dopamine (this can be referred to as tolerance). There are many changes in neurotransmitters other than dopamine. Long-term drug abuse causes changes in other parts of our brain chemical system, for example in glutamate which is a neurotransmitter that affects the ability to learn and again affects the reward circuitry. When optimal concentration is altered by drug abuse, the brain tries to compensate, which can cause deterioration in cognitive function. It must be remembered that it modifies critical areas of the brain such as our judgment, memory, learning, behavioral control and decision making.