The brain relays messages to other parts of the body to ensure their functionality. The brain controls everything that happens in your body. It tells your stomach to digest food and your lungs to breathe air; it tells your arms and legs to move.
Your brain is made up billions of nerve cell networks connected in groups known as neurons. Action potentials, which are electrical signals sent by neurons to each other via axons, allow them to communicate with one another. Every neuron has a cell wall around its nucleus. The cell membrane houses channels that allow ions, such as potassium and sodium, to enter and exit the cells. Ion movement creates the electric charge that causes the neuron to fire.
When a neuron fires, chemicals called neurotransmitters are released into the space between the neuron and the next neuron. Neurotransmitters attach to the receptors of the second neuron and open ions channels for ions to pass in and out. In turn, the second neuron also fires.
Neurotransmitter releases occur when a presynaptic neurons receives an input from another neuron. An impulse travels along a synaptic link between the two neuron. The transmitter binds to the receptors on the postsynaptic neural cell, which triggers the firing of that neuron.
For communication within the nervous systems, neurotransmitters are essential. They also coordinate activity between different brain parts.