Impulses are sent within a neuron. Electrical charges are sent from dendrites all the way down to the axon But there's also communication between neurons; electrical charges are used to transmit information within the cell.
Taking a closer look at the areas between different neurons, you can see that at the very end of an axon of one neuron is a little button area, called the axon terminal. Normally an axon sends an electrical impulse across the cell, but this electrical impulse is not transmitted to other neurons. The reason why, is that in between the axon and the dendrites of other neurons there is this space, which we call a synapse. There's an actual gap right between these different cells. The electrical impulse can't jump over to other cells.
Instead, when that electrical impulse reaches the axon terminal, it releases what are called neurotransmitters. Neurotransmitters are chemical messengers that attach themselves to other dendrites of other neurons surrounding them. This is helpful because it allows one neuron to communicate with many different neurons by sending out all of these different chemical messengers. It's not just one-to-one, it could be one to potentially hundreds of neurons.
These neurotransmitters attach themselves to dendrites at what are called receptor sites. And these receptor sites act as a sort of lock-and-key mechanism. So one neurotransmitter fits that one receptor site. It's not a one-size-fits-all kind of thing. All of these different receptor sites receive all of these neurotransmitters and eventually, when this neuron on the other side of the synapse, when this neuron receives enough chemical messengers, it activates itself and releases into an action potential, which fires this different neuron and then potentially other neurons surrounding it. You can imagine how it creates a cascade effect, one neuron potentially affecting a lot of different neurons.
There are many different types of neurotransmitters that are used in the brain and the nervous system. Remember, it's not a one-size-fits-all kind of thing. The reason for this is to allow for various effects within the brain and the rest of the body itself.
Two general types of neurotransmitters are excitatory and inhibitory. Excitatory neurotransmitters, lead to the threshold of excitation, firing of neurons and ultimately, action potential. Inhibitory neurotransmitters prevent the firing and it keeps that resting potential instead. It doesn't allow the other neurons to fire.
The most common type of neurotransmitter is acetylcholine, which is abbreviated as ACH. This is an excitatory neurotransmitter. It's used within the body to help with the muscle movement as well as the activation of the peripheral nervous system in different ways. In the brain itself, it's attached to attention and memory.
One of the more famous neurotransmitters is dopamine. Dopamine is used especially in certain areas of the brain, the frontal cortex and the limbic system, and this plays a role, particularly in motivation of people as well as reward and reinforcement systems within the brain. Dopamine leads to a lot of addictive behaviors. Addiction to gambling or alcohol is generally a result of dopamine being activated too much within the brain. This is also chemically similar to cocaine.
There is a class of neurotransmitters called neuropeptides, which are a special group that regulate certain activities of neurons and systems within the brain itself.
Source: This work is adapted from Sophia author Erick Taggart.
The small space between the axon terminal of one neuron and the dendrites of other neurons.
Chemical messengers that allow neurons to communicate with other neurons across the synapse.
Areas on neurons that connect and respond to neurotransmitters.
The most common neurotransmitter, which is used in movement in the peripheral nervous system and related to attention and memory in the brain.
A special class of neurotransmitters that regulate the activity of neurons and systems in the brain.
The level or point at which a neuron fires, or a neural impulse is triggered.
The state in which a neuron is not firing or sending a neural impulse and when there is a negative electrical charge inside the neuron.
The state in which a neuron reaches its Threshold of Excitation and fires, or sends an electrical impulse down the axon.