Natural Reward Pathways (Section 1)
Neurons are in charge of transmitting neurotransmitters through the brain. They have specific functions such as holding memories and muscle control. The brain has many sections, in the middle of the brain is a section known as the reward pathway. This region is in charge of the emotions motivation, reward, and behavior. It's main role is to "reward" us by making us feel content when we commit an act or behavior beneficial to our life such as eating, drinking, and sex. The reward pathway has connections that let it know what is going on outside the body. The connections also makes the brain circuits that regulate desirable behavior stronger. Our senses of taste, touch, smell, sight, and hearing allow us to obtain knowledge of our environment/surroundings and let our brain know through signals that there may be something desirable near us. There is another section in our brain that contains a memory that tells us once you eat you are not hungry any more and you are feeling pleasant. Our senses notify the brain that you are eating tasty food and filling up your appetite. Special neurons release dopamine and give you a jolt of happiness. Thus you are rewarded for eating food. Not only do you feel pleasure, but you are encouraged to do this behavior again whenever you can by the reward pathway through connections to memory and behavior regions. The wiring for behaviors that aid you in your rewarding are strengthened when the reward pathway notifies the motor center of the brain. Thus the feeling of happiness makes us want to repeat our behaviors, and keeps us alive.
The synapse is what sends neurotransmitters from neuron to neuron. Scientists previously thought that neurons were the most valuable brain cells. Now it is known that there are other cells that have important contributions to brain functions.
Drugs Alter the Brain's Reward Pathway (Section 2)
Any drug that is addictive always alter the brain's reward pathway. Some examples of some drugs of abuse are: alcohol, steroids, cocaine, GHB & Rohypnol, hallucinogens, heroin, inhalants, marijuana, methamphetamine, ecstasy, and nicotine. All of these drugs have addictive qualities and terrible side effects. The synapses in the brain undergo immense changes seconds after the drug enters your system. (The faster the drug enters you, the more addictive it is.) The drug activates the reward system and makes you feel a sudden happiness or pleasure. This happens because the drug is able to trick cells into transmitting lots of dopamine in the synapse, which brings that jolt of pleasure. The brain is stimulated so immensely that it tries to develop a coping mechanism. The brain tries to lessen the amount of dopamine receptors so that the person using the drugs "comes down" and will need more of the drug to get high. This action by the brain is known as tolerance. As the brain changes and alters to adapt, other parts of the brain besides the reward system begin to get affected. Some examples of sections of the brain that are affected when the brain adapts are the judgement, memory, and learning sections. They become hard-wired, meaning getting drugs becomes a reflexive habit. The drug user becomes a drug addict. In brains addicted to meth, neurons on the exterior of the brain reward system have especially long and thick dendrites compared to a normal brain dendrite. Some other pathways affected besides the reward system are the dopamine and serotonin pathways. Serotonin controls happiness, so it is commonly used in antidepressants. Then there is glutamate and gamma-aminobutyric acid (GABA). They are both neurotransmitters that work together to regulate multiple processes in the body. Glutamate begins action potential and GABA ends it. Many addictive drugs affect glutamate and GABA resulting in stimulating effects. Drugs are so overwhelming to the brain and body that even a slight overdose will overload the body and kill you. Glutamate and GABA control many of the important processes in the body, as aforementioned, and one of them is the regulation of breathing. Drugs will decrease/increase the glutamate or GABA and make you stop breathing. Which results in death.