Your body contains a large network of nerves, which carry electric signals to and from your brain. The signals going FROM the brain control your muscles so you can move around, talk, and keep your balance.
The signals going from your body TO the brain bring information about the outside world. When your brain processes this information, it allows you to see; to feel different sensations; and to hear, smell, and taste.
If you look at the brain under a microscope, you will see that it is actually made up of over a trillion cells. There are two types of brain cells: glial cells and neurons, or nerve, cells. Glial cells are the brain's support network. They help maintain the environment surrounding neurons and are responsible for myelin, a fatty substance that insulates nerve cells in order to speed up communications. Neurons, on the other hand, are the messengers of the brain. Their job is to take information and move it as quickly as possible from one cell to another.
There are billions of neurons in the brain, sending and receiving information that make up our thoughts, control our behavior, regulate our bodies, and more. So how are all these neurons able to communicate? They do it through a combination of electrical and chemical signals.
When a neuron is activated, an electric signal is sent from one end of the neuron to the other. As it gets closer to the other side, this neuron can split into many fine branches. At the end of these branches, chemicals called neurotransmitters are stored in specialized swellings.
When the electrical impulse reaches these swellings, it signals the release of neurotransmitters into the space between the two neurons. This space is called a "synapse." The outer surface of the other neuron is covered with receptors. Neurotransmitters cross the synapse and fit into receptors like a key opening a lock. When this connection is made, it signals the next neuron. Some neurotransmitters will tell the next neuron to create an electrical impulse. Others will prevent a neuron from creating an electrical impulse.
The average neuron forms about 1,000 connections with other neurons, which means there are a lot of different chemicals floating around in the synapse. So how does each neuron know what to do when its receptors are activated?
The receptors on a neuron's surface will only connect with the specific type of neurotransmitter that has the right chemical shape. Neurotransmitters that do not have the right "fit" will not bind to the receptor and, therefore, will not cause a response.
And a neuron will only respond when enough neurotransmitters have fit into its receptors. Whether the neuron sends a signal depends on the amount and type of neurotransmitters that have connected to its receptors.
Once the neurotransmitters have done their job, the majority of them return to the neuron that sent them, clearing the synapse for the next signal. This is called "reuptake."
Even though this seems complicated, the entire information transmission process occurs in the brain and other parts of the nervous system within a matter of seconds.