Source: Synapse Images; Public Domain http://1.usa.gov/Ve0kLx
Hello, class. So remember we're talking about the nervous system. It's essentially the body's communication system. It allows information to be sent to and from our brain and allows us to control the rest of our body. So it allows us to send all of these messages, which allow us to do all the things that constitute our mind and behavior.
And there are two different ways that we communicate. There are ways that impulses are sent within a neuron. Electrical charges are sent from the dendrites all the way down to the axon. But there's also communication between neurons. So neurons use those electrical charges to transmit information within the cell.
But how do they actually communicate between other cells to send information to lots of different ones? Which allows us to create the entire system of our brain and our nerves and all these different neurons. Well we're going to explore that more today.
Now taking a closer look at the areas between different neurons, we can see that at the very end of an axon of one neuron we end at this little button area, which we call it axon terminal. Now 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. So there's an actual gap that occurs right between these different cells. So the electrical impulse can't jump over to other cells.
We need another way to communicate with those cells. So instead, when that electrical impulse reaches the axon terminal, it releases what are called neurotransmitters. And neurotransmitters are chemical messengers that attach themselves to other dendrites of other neurons surrounding them. And this is helpful because it allows one neuron to communicate with lots of different neurons by sending out all of these different chemical messengers. So it's not just one-to-one, it could be one to potentially hundreds of neurons.
Now 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. Now 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. So you can see how it creates a cascade effect. One neuron can potentially affect lots of different neuron.
Now as I said, there are lots of different types of neurotransmitters that are used in the brain and the nervous system. As we said, it's not a one size fits all kind of thing. And this allows for lots of different of effects within the brain and the rest of the body itself.
Now generally with neurotransmitters we have two different types. There are excitatory neurotransmitters, which lead to the firing of neurons. So it leads to that action potential. And there are inhibitory neurotransmitters, which prevent the firing and it keeps that resting potential instead. It doesn't allow the other neurons to fire.
Now we're going to look at some examples of different neurotransmitters as well as their effects within the brain. Now the most common type of neurotransmitter is acetylcholine, which is abbreviated as ACH. This is an excitatory neurotransmitter. And it's used within the body to help with the movement of our muscles as well as the activation of our out peripheral nervous system in different ways. In the brain itself, it's attached to attention and memory and things like that. And it's thought that a lack of acetylcholine can contribute to Alzheimer's disease.
Now one of the more famous neurotransmitters is dopamine. And 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. So dopamine leads to a lot of addictive behaviors. When we say we're addicted to gambling or alcohol, things like that, generally it's a result of dopamine being activated too much within the brain. This is also chemically similar to cocaine. So a lot of drugs will act like dopamine and lead to all these feelings of pleasure.
And we also have a class of neurotransmitters called neuropeptides, which are a special group that regulate certain activities of neurons and systems within the brain itself. An example of one is an endorphin. An endorphin acts to reduce pain and it leads to feelings of euphoria or feeling very positive and good about yourself, especially when we feel pain or we're stressed out. So these endorphins are what results in a runner's high. So when we're running and all of a sudden you get this feeling of just feeling really, really great and really good about yourself, that's the result of endorphins be activated within your brain.
Terms to Know
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 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 level or point at which a neuron fires, or a neural impulse is triggered.
The state in which a neuron reaches its Threshold of Excitation and fires, or sends an electrical impulse down the axon.
Small tunnels along a neuron that to pump ions from one side of the cellular membrane to the other, which creates an electrical charge.