Other molecules called transportersВ recycle neurotransmitters (that is, bring them back into the neuron that released them), thereby limiting or shutting off the signal between neurons. This causes changes in the receiving cell. The neurotransmitter crosses the synapse and attaches to receptors on the receiving neuron, like a key into a lock. To send a message, a neuron releases a neurotransmitterВ into the gap (or synapse)В between it and the next cell.

Networks of neurons send signals back and forth to each other and among different parts of the brain, the spinal cord, and nerves in the rest of the body (the peripheral nervous system). Different brain circuits are responsible for coordinating and performing specific functions. The brain is made up of many parts with interconnected circuits that all work together as a team. If a neuron receives enough signals from other neurons that it is connected to, it fires, sending its own signal on to other neurons in the circuit. Each neuron acts as a switch controlling the flow of information. Instead of electrical circuits on the silicon chips that control our electronic devices, the brain consists of billions of cells, called neurons,В which are organized into circuits and networks.

The brain is often likened to an incredibly complex and intricate computer. In short, your brain is you-everything you think and feel, and who you are. The brain regulates your body's basic functions, enables you to interpret and respond to everything you experience, and shapes your behavior. This three-pound mass of gray and white matter sits at the center of all human activity-you need it to drive a car, to enjoy a meal, to breathe, to create an artistic masterpiece, and to enjoy everyday activities. The human brain is the most complex organ in the body.

How many neurons are in the brain