The brain communicates with itself by transmitting chemicals from one neuron, or nerve, to the other. And this regular, rapid-fire messaging plays a big role in how you feel and function each day.\nThese neurotransmitter chemicals are classified into two basic categories: excitatory, meaning they stimulate brain activity, or inhibitory, meaning they have a more calming effect. Learn more about a few common brain chemicals and how they impact your thinking and mood.\nFour Important Brain Chemicals\n\nSerotonin\nYou probably already know that serotonin plays a role in sleep and in depression, but this inhibitory chemical also plays a major role in many of your body\u2019s essential functions, including appetite, arousal, and mood. Many antidepressants target serotonin receptors to improve your mood and lessen depressive symptoms.\nInterestingly, most of your serotonin is stored in the intestine, and this chemical may play a role in digestive functioning as well.\nDopamine\nDopamine controls many functions, including behavior, emotion, and cognition. This chemical also communicates with the front part of your brain, which is associated with pleasure and reward. On the positive side, it helps motivate you to work toward achieving a reward. However, many illegal drugs also target dopamine receptors, contributing to drug and alcohol addiction. Because dopamine is related to movement, low levels have also been linked to Parkinson\u2019s disease.\nGlutamate\nThis is the most common excitatory neurotransmitter, found throughout your brain and spinal cord. Glutamate has many essential functions, including early brain development, cognition, learning, and memory.\nNorepinephrine\nThis chemical, also called noradrenaline, can sometimes act as a hormone as well. Its primary role is part of your body\u2019s stress response. It works with the hormone adrenaline to create the \u201cfight-or-flight\u201d feeling. Norephinephrine may also be used as a drug to raise or maintain blood pressure in certain illnesses.\nChemicals, Hormones, and the Brain\nSome of these neurotransmitters, such as norepinephrine, are also hormones or have some effect in releasing hormones in the body. Adrenaline, cortisol, melatonin, and other hormones can affect your mood or even influence the health of your brain.\nCortisol is a hormone released when you\u2019re stressed. It\u2019s helpful at times, but too much of it for too long can cause memory loss as you age.\nImbalances in neurotransmitters are present in many conditions, including schizophrenia, depression, bipolar disorder, autism, and Parkinson\u2019s disease. Some medications target these receptors to allow your body to receive more or less of certain chemicals, while some drugs act similar to these chemicals to invoke similar responses in your body.\nMaintaining a balance in these brain chemicals and hormones is key to feeling a balanced mood. You can help maintain this health to some extent through a balanced diet, limited stress, and exercise.