Neurotransmitters are chemical messengers that transmit signals across synapses between neurons in the nervous system. They significantly influence behavior, mood, and cognitive functions by binding to specific receptors on post-synaptic neurons. Different neurotransmitters, such as serotonin, dopamine, and norepinephrine, play distinct roles in regulating emotional responses, motivation, and learning. Imbalances in neurotransmitter levels can lead to various mental health conditions, such as depression or anxiety, highlighting their critical role in psychological health and overall behavior.