Hi Hi What's up? how are they? Welcome to a new anatomical video on this channel easy anatomy by Juan José Sánchez.

Today I bring you a series of videos of the sympathetic nervous system in general, we are going to see in this first installment of the sympathetic nervous system 1 we will talk about the generalities of the system, how it is composed, what its general actions are, in a second installment we will talk only of the sympathetic ganglionic chain, where it is located, how it is divided into ganglia that are prevertebral and ganglia that are lateral vertebral and in the third and last installment of the sympathetic nervous system we will address how it works, what its afferent pathways are like and what are its efferent pathways like, this of the nervous system as such because in the specific ganglionic chains there are already specific videos of the cervical sympathetic chain, the thoracic sympathetic chain, the lumbar sympathetic chain and the sacral sympathetic chain, as well as the ganglia that we find for example in the solar plexus, superior and inferior gastric plexus, those videos are separate on the channel, here then we will talk about the sympathetic nervous system in general. Very well, the way of classifying where this sympathetic nervous system or sympathetic division comes from, well the nervous system in general is divided into a central nervous system and a peripheral nervous system, we already made videos of the central nervous system, we know what it is. who commands and is composed of the brain and the spinal cord, while the peripheral nervous system, which is the one that connects the central with the periphery with the rest of the body, is the one that is made up of the somatic nervous system and the autonomic or vegetative nervous system, this The somatic nervous system, in turn, would then be made up of spinal nerves and the cranial nerves.

I already made a video on generalities of the peripheral nervous system where I generally explained these two components. Now we are going to be more specific talking about the autonomic or vegetative nervous system, which is the one made up of the sympathetic nervous system, with our videos that follow and a video dedicated to the parasympathetic nervous system because it is actually shorter and easier to explain; very good, what is the sympathetic nervous system? what does it consist of?

Well, we know that this sympathetic nervous system is one of the two subdivisions of the autonomic nervous system along with the parasympathetic and in general it is responsible for, let's say, carrying out all the actions that I cannot control at will and it works, let's say, by giving those connections through some substances that are mediators, which are communicating substances that we call neurotransmitters, specifically the neurotransmitter that is involved in the sympathetic nervous system is adrenaline, also called epinephrine, and noradrenaline, also called norepinephrine, which are the two neurotransmitters that we will always see that are involved in the sympathetic nervous system, then this sympathetic nervous system, which is the little brother of the parasympathetic because the two are derived from or are what make up the autonomic nervous system, generally has effects that are opposite in the parasympathetic nervous system and I say generally because, for example, in the In the case of the reproductive system, we know that the sympathetic system stimulates ejaculation, the parasympathetic system stimulates the erection, so for that function they have to be agonists, they have to help each other and not be opposites, but in most cases of the other organs we will see that the sympathetic to the opposite of parasympathetic. So this sympathetic nervous system, as I told you, controls the parts of the body that I cannot control, the will, all the viscera, the organs, we are going to see them, all the glands that produce saliva, produce mucus, produce the pancreas, produce bile, any exocrine or endocrine gland, any organ, heart, lung, small intestine, large intestine or liver all controlled by the autonomic nervous system, then as a general rule we say that the actions of the sympathetic nervous system are those that are like flight responses and alert, you always, I always tell students to imagine that they are in a situation where they are robbed, a situation where your life is in danger, all the actions that the body does at that moment are mediated by the sympathetic, while when we are in a general state of rest our day to day life is governed, as we say colloquially, by the system parasympathetic nervous system , which is what controls our basal state, so when we want to experience all that increased heart rate, dilation of the bronchi, dilation of the pupil, inhibition of intestinal movements, all of this is mediated thanks to the fact that whoever is taking The control in our body at that moment is the sympathetic one. Very well, this sympathetic nervous system, it is important to know that remember that it is part of the peripheral nervous system, so it derives from the central nervous system, okay?

What part of the central nervous system has the nuclei of origin or the autonomic centers from which the sympathetic nervous system arises? specifically the spinal cord, it is called thoracic and lumbar but it is not specifically the thoracic and lumbar or not all of the thoracic and all of the lumbar, we are going to see that the ganglia, the large ones but in the centers begin between the c8 spinal cord segment and the spinal cord L2, see that I am not talking to you about the spinal nerves, I am not talking to you about vertebrae, but about the segments of the spinal cord, which are segments that we already explained in the spinal cord video, so in the last segment of the cervical segment, which is the c8 segment, I repeat, do not confuse it with the c8 vertebra because it does not exist, the vertebra is up to c7 and the last segment of the cord, which since it has sympathetic information, is the L2 segment, of course because it is also at that level The spinal cord is practically running out, so what remains is the cauda equina of the more or less lumbar segment downwards, what is going to happen? When we studied the spinal cord, we realized that the spinal cord sections at the thoracic level characteristically had this horn, which is the intermediate lateral horn, well this intermediate lateral horn, which is made of gray matter than the one we found in the sections of the spinal segments between c8 and L2 are where the fibers are, the neuronal centers that begin or command the sympathetic nervous system, that is the part of the central nervous system that commands then those spinal segments that originate the sympathetic figure, they have to seek communication with ganglia that will be found very close to it, which are the famous ganglia of the sympathetic chain.

We are going to explain what these ganglia are, where they are located, but first do not go away from the video [Music] so it is important that you subscribe to the channel, down here where you see that it says subscribe click and you are automatically subscribed to all the videos of the channel, if there is a video that you don't get on the channel, they write everything in the comments, which they always took into account when making them. We had then stayed in the sympathetic trunk, which is a chain of ganglia that is parallel, it is close to the spinal column because that is where the sympathetic centers of the spinal cord are, so this sympathetic trunk is a chain of ganglia that are interconnected between Yes, we find those sympathetic chain ganglia from above the base of the skull to the first cervical ganglion c1 down to the coccygeal level where the right side joins with the left side in a last ganglion called the odd ganglion, which is what what's happening? This sympathetic chain can carry an impulse both upwards and downwards interchangeably, but it is said that the nervous impulse can be bidirectional and the ganglia that compose it are nervous ganglia, they should not be confused with lymph nodes, these are nervous ganglia; These nervous ganglia are relay stations because the information then comes from the spinal cord to the ganglion, which will be a synapse, a nervous relay, and from the ganglion comes another nerve, which is, let's say, the nerve that will finally exert the sympathetic action in this case.

Because the sympathetic uses ganglia, it is one of the big differences, visible ganglia rather, there are no big differences between the sympathetic and the parasympathetic or the peripheral, what is going to happen? See what we say that the start of the system Sympathetic is in the thoracic and lumbar cord but the entire body has sympathetic information, both the head and the lower limbs to tell you something, extremes, but all the sympathetic information that goes to the head has to be born in the thorax, it is not that it is born in the head, that is why the information that generally comes through the cervical sympathetic chain, they believe that here in the middle you see this one that is here medial, the information that comes with it is information that comes from the bottom up and therefore For example, all the information that is born below the sympathetic L2 comes down the sympathetic chain, which does reach down to the tailbone; What I want you to know is that the information can go up and it can also go down and that they will always be born in the thoracic cord, specifically the lumbar cord, the segments from c8 to L2. So it is assumed that more or less in theory each ganglion corresponds to a vertebral segment with a medullary segment, but we see that in practice this is not always the case, because these ganglia are generally fused together so there is less ganglion than nerves, because they begin to merge with each other.

Now, see for example, here this is a cut at the thoracic level, I know it is thoracic because I see a lung here and because well the nerves are born here, look at this thoracic cut I see the intermediate lateral horn in the gray medulla, a medullary gray matter and there the sympathetic information comes out that travels through a spinal nerve and here you see how it searches for its ganglia, its relay station through the communicating branches to make the synapse and from there it innervates more structures than good. We will see in the following videos of the sympathetic nervous system, what I want you to know is that here the ganglion is born and takes over, how close the ganglion is to the spinal cord to be able to make, let's say, the allocation a little more efficient, we see here for example Again, the ganglionic chain that comes is in the neck and is low at the lumbar level, but see that it always originates, always originates at the thoracic and lumbar level, and in this case the fibers are going to go up the cervical sympathetic chain to be able to reach the neck and reach head on, okay? That is why when you cut or damage the cervical sympathetic chain, the upward innervation is lost because the information does not come from the top down, but rather it comes from the bottom up when we talk about the sympathetic and a particularity of that.

Now what are the general actions of this nice guy? I'm going to explain quickly from top to bottom, for example, at the level we see a lot that governs, remember, the entire body, all the smallest gland that you can imagine is governed by the sympathetic, so for example at the level of the eye, the pupil is dilated by the sympathetic. okay?

It dilates it thanks to the fact that when I want to flee, it dilates the pupil to further increase my field of vision; The salivary glands are governed by the sympathetic. In this case, the function that the sympathetic does to the salivary glands is to inhibit them so that they do not cause saliva; In the case of the heart, the heart rate increases, the force of contraction increases and, let's say, the pumping efficiency of the heart increases; At the level of the lungs, it dilates the bronchi so that more air reaches you because it is always assumed that you are going to flee, the heart beats faster because you are going to flee and it needs to bring more blood to the muscles so that they have more energy and can help you. run; In the case of the digestive system, peristalsis is inhibited, intestinal movements are inhibited because at that moment what I want is to spend energy on an intestine that is contracting.

With respect to the adrenal glands, well, I stimulate the adrenal medulla because There is a lot of adrenaline there and remember that the sympathetic person needs adrenaline to exert their action; in the case of the kidney, urine production decreased; In the case of intestinal emptying, it decreased, I don't care at that moment, that's why you see that when it's sympathetic, the less you feel like going to the bathroom, both at the level of the bladder it prevents its emptying and at the intestinal level and at the good genital the sympathetic has a lot to do with ejaculation, a lot to do with ejaculation, So, let's say general actions of the sympathetic nervous system, each organ would have to be studied specifically to know what it does to each one. This was then the entire video of the first installment of the sympathetic nervous system. I hope you liked it.

Don't forget to subscribe to the channel. Like the video if you liked it and you can search for my Instagram at @juan_sanchez1315.