Neurotransmitter systems are networks in the brain that use chemical messengers called neurotransmitters to communicate between nerve cells, or neurons. These chemicals are released from one neuron and bind to receptors on another, allowing signals to be transmitted throughout the nervous system. Different neurotransmitters, such as serotonin, dopamine, and glutamate, play specific roles in regulating mood, movement, and cognition. Each neurotransmitter system has distinct pathways and functions. For example, the dopaminergic system is involved in reward and pleasure, while the serotonergic system affects mood and anxiety. Understanding these systems is crucial for developing treatments for various neurological and psychiatric disorders.