Neuromuscular Junction (Nursing)

00:00 Number one is the axon. Now, you're used to seeing this with other neuro cells, but it's a long slender projection of a nerve cell or a neuron. It's the kind of arm that comes off it. So, that's what the axon is. Now, what it does is it conducts electrical impulses known as action potentials. So, when you see those words that's all that means. Action potential is just that electrical impulse travelling down the axon. It's away from the nerve cell body. So, you have the cell body and the axons that project off it. Their job is to conduct the electrical impulse away from the nerve cell body. Now, this function transmits information to the different neurons, muscles, and glands. Since we are talking about the neuromuscular junction, we're talking about how it is transmitting the information to the muscles. So, that is the axon's job.

00:53 The body and the axon that extends off of the body, that's what the role is. Now, as we're going through this, you may want to pause and recall. Stop the video at a point where you feel like woah, that's enough, and just see if you can recall and reflect what each of the functions are of these 4 important parts of the neuromuscular junction. Stop. Number 2 is the motor endplate. Remember, we introduced that in the introduction, talking about the acetylcholine receptors. Now, number 3 and number 4. Number 3 is the muscle fiber. Number 4 are the myofibrils. Now, that matters. We have got number 1, that's the axon; number 2, that's the motor plate; number 3 is the muscle fiber; but number 4 is the myofibrils that are inside that muscle fiber. So the muscle fiber is a tubular cell. It's called a myocyte. So, that's pretty important that you remember that word, so it's familiar to you when you see it in other drawings and discussions. So, it's a tubular cell, look at that, looks like a tube or like a pipe, and it's called a myocyte. Now, it has lots and lots of chains of myofibrils. Remember, that's number 4. Those are all myofibrils. So the muscle fiber, which is a myocyte, has many, many chains of myofibrils in striated muscle. So, myofibrils are the basic rod-like unit of a muscle cell. Alright, now just for fun, pause the video and cover up the words and see if you can recall the name and the function of the 4 stops in the neuromuscular junction. Okay, now let's break it down even more. You have those 4 major areas. I want to take a closer look at the neuromuscular junction. Now, you can see we have taken out a little small box, and we've blown it up so you can take a look at it. Now, number 1 represents the presynaptic terminal. We can look at the prefix. It's p-r-e. That means before the synaptic terminal. So, that's before the synapse. Number 2, that's the sarcolemma. Now, look at that as it goes across. The cell membrane of a striated muscle fiber cell is called the sarcolemma. So, it's a cell membrane, and you see that there in the drawing. Now, number 3 is the synaptic vesicles.

03:22 Now, this is for the neurotransmitter vesicles, so synaptic vesicles or neurotransmitter vesicles. Now, this is where you store the various neurotransmitters that are released at the synapse. Okay, so you've got the presynaptic terminal, the sarcolemma that's just the cell membrane, and the synaptic vesicles are number 3. They are also called neurotransmitter vesicles, and they store the neurotransmitters that are then released at the synapse.

03:52 Number 4 is the nicotinic acetylcholine receptors. Now, look at this. We've got the nerve and the muscle, right? So, the receptors are these polypeptides that respond to the neurotransmitter acetylcholine. Okay, now if that's starting to get confusing, let's go back over just briefly once again. In the gray color, we're talking about that axon. Right? That's the nerve. Then at the bottom, you have the muscle. So, we've got these receptors. Where are they located? Number 4. These are acetylcholine receptors. When they receive the neurotransmitter acetylcholine, that activates them and allows you to move your muscles. So, this is where the nerves control the muscles. Stop 4 is the nicotinic acetylcholine receptors. Now, the 5th one is the mitochondrion. Everyone remembers this from junior high. Right? It's the cell's powerhouse. People that don't even like science usually remember the mitochondrion is the cell's powerhouse. That's because they generate most of the cell's supply of chemical energy known as ATP or adenosine triphosphate.