Welcome to this lesson today on neurotransmitters. Today you will be learning about the role of neurotransmitters in relaying signals throughout the nervous system. Specifically, you will look at:
First, you’re going to learn about how neurons communicate. Specifically, how neurons communicate with muscle fibers in order to set the stage for muscle contractions.
An action potential will flow along the axon of a motor neuron to a neuromuscular junction; a neuromuscular junction is basically the area where a neuron and a muscle fiber come close to one another. The neurotransmitters will then diffuse across a gap known as a synapse.
Remember, the neurotransmitters are the chemical form of whatever signal is being carried. These neurotransmitters will diffuse across the synapse or the gap between the axon endings of the neuron and the muscle fiber plasma membrane. These are called the presynaptic and postsynaptic cells. The synapse is the gap in between the axon ending of the neuron separates the axon ending of that neuron from the muscle fiber.
The cell that's before the synapse is called the presynaptic cell and the cell that is after the synapse is called the postsynaptic cell. Neurotransmitters will carry that information from the presynaptic cell across the synapse to the postsynaptic cell. From there, those neurotransmitter molecules will bind to receptor proteins on the postsynaptic cell and allow channels to open. Ions can then diffuse through those channels and an action potential can occur.
Neurotransmitters can either excite or inhibit activity in a target cell. So basically, whether they excite or inhibit is determined by the amount of the neurotransmitter, the type of the receptor, among other factors. Exciting signals will drive a membrane toward an action potential, while inhibiting signals will do the opposite.
Take a look at a diagram here so you can understand this a little bit more in detail.
So what you have here is a picture of a motor neuron. So the information will travel along the axon to the axon endings. So right here you’ve basically zoomed in on an axon ending.
Then you have in here your synaptic vesicle. And these synaptic vesicles are what contain neurotransmitters. The line is your muscle fiber. Above the muscle fiber line is the presynaptic cell and below the muscle fiber line is the the postsynaptic cell. The gap in between them is the synapse.
The neurotransmitter is going to carry information from the presynaptic cell across the synapse to the postsynaptic cell, which is the muscle fiber in this example. You also have the plasma membrane of this muscle fiber and these proteins that are embedded in the plasma membrane. On those proteins you have this binding site for neurotransmitters.
Now you'll notice when the binding site is empty, when there's nothing there, the ion channels are closed. But when a neurotransmitter binds to the binding site, it causes that ion channel to open so then ions can flow through the plasma membrane and then allow for an action potential to occur. So the neurotransmitters are carrying information from the presynaptic cell to the muscle fiber, binding on these sites, allowing the ion channels open and allowing an action potential to occur. So this is the way in which neurons can communicate with muscle fibers. But neurons can also communicate with other neurons or with gland cells as well.
Botox is a type of injection that people get to smooth out facial wrinkles and it's actually made from a bacterium.
What it does is it blocks the release of acetylcholine so that the muscle contractions that produce wrinkles will stop temporarily, and acetylcholine is a type of neurotransmitter.
People get this in order to stop or slow down facial wrinkles.
So this lesson has been an overview on neurotransmitters. Specifically, you learned about how neurons communicate and that neurotransmitters can either excite or inhibit activity in a target cell.
Keep up the learning and have a great day!
Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND
A bacterial toxin that is often used to smooth facial wrinkles by stopping the release of the neurotransmitter acetylcholine.
Signals that trigger an action potential to happen.
Neurotransmitters that inhibit or prevent action potentials.
The chemical form of a signal that is sent between neurons and muscle cells, gland cells or other neurons.
The cell at a synapse to which the neurotransmitter binds.
The cell at a synapse that stores a neurotransmitter for release.
The gap between a neuron and a gland cell, muscle cell and another neuron.