To explain the communication process of neurons in the brain we must first understand the how a neuron works. In view of the fact that neurons form a network of electrical activities, they somehow have to be interconnected. When a nerve indicator, or impulse, reaches the ends of its axon, it has traveled as an action potential, or a pulse of electricity. However, there is no cellular continuity between one neuron and the next; there is a breach called synapse. The membranes of the sending and receiving cells are separated from each other by the fluid-filled synaptic gap. The signal cannot leap across the gap electrically, so special chemicals called neurotransmitters provide this role.
As an electrical impulse travels down the extension of the cell, called the axon and arrives at its terminal, it triggers vesicles containing a neurotransmitter to move toward the terminal membrane. The vesicles fuse with the terminal membrane to release their contents. Once inside the synaptic cleft, the space between the two neurons, the neurotransmitter can bind to receptors on the membrane of a bordering neuron.
Chemically, neurotransmitters are relatively small and simple molecules. Different types of cells secrete different neurotransmitters. Each brain chemical works in specific brain locations and may have a different effect according to where it is activated. After these molecules cross the tiny synaptic gap between neurons, they bind to receptor sites on neighboring neurons, thus passing on their excitatory or inhibitory messages.
Different neurotransmitters have different effects on behavior and emotion. For example, release of acetylcholine, the neurotransmitter found at every junction between a motor neuron and a muscle, causes the muscle to contract. Acetylcholine (ACh) released at the neuromuscular junction, plays an important role in arousal and attention. A loss of ACh producing cells is thought to be linked to Alzheimer's...