Sympathetic Nervous System - Online Tutor, Practice Problems & Exam Prep

The sympathetic nervous system, activated during stress or physical activity, triggers a "fight or flight" response. Key effects include increased heart rate, bronchiole dilation for enhanced airflow, and glucose release from the liver for energy. Blood flow is redirected from the gastrointestinal tract to skeletal muscles, while pupils dilate for better vision. Preganglionic fibers, originating from T1 to L2, synapse in ganglia, with pathways varying in synapse location. Splanchnic nerves bypass the sympathetic trunk, innervating abdominal organs, while the adrenal medulla releases epinephrine, crucial for the stress response.

Function of the Sympathetic Nervous System

In this video, we're going to be talking about the function of our sympathetic nervous system. So I'll be going over some of the effects that it has on our body. I'll talk about how those effects may be helpful for us in a potential fight or flight situation. As a reminder, this division becomes activated when we are engaged in physical activity or have to perform under some kind of stress or threat. One major effect that we're going to see is an increase in heart rate, and that of course will also increase blood pressure, which is going to have blood pumping faster through our body delivering oxygen to our muscles much faster. We're also going to see a dilation of the bronchioles in the lungs, which will increase airflow and increase oxygen intake. Our liver is going to begin releasing glucose into the blood, and that will act as an energy source for our muscles, should they need it.

One kind of weird effect that we see is that we're going to see a contraction of the arrector pili muscles, which are tiny muscles around your hair follicle. And when they contract, we get goosebumps. And if you're wondering, like, why do we need goosebumps if we're under threat? The answer is we don't, but our evolutionary ancestors probably did. We think it's just left over from evolution. So, you know how when a dog or a cat becomes threatened, they kind of puff up their fur to look bigger and scarier? We think that that's basically what this was. Way down the line, we had an ancestor that was covered in hair and they could kind of puff up to look scary when they were threatened. And over time, we lost the hair but we did not lose those goosebumps. So, kind of a fun fact, right?

Next, we're going to see a decrease in gastrointestinal activity. That is considered a non-essential function when we're in kind of a stressful or threatening situation. So that gets kind of put on hold. Regarding our blood vessels, we're going to see a vasoconstriction in visceral vessels; vessels going to the stomach or intestines, that's all going to get less blood flow, and we're going to see vasodilation to our skeletal muscles. These skeletal muscles are going to get more blood flow, more oxygen delivery, more nutrients, more glucose, to help them perform under stress. We're going to have our pupils dilate, which will, of course, allow more light to enter our eye and allow us to potentially scan our environment for threats. Lastly, we're going to have a stimulation of the sweat glands, everyone's favorite stress response. We think that this probably happens because many of these processes, for example, an increased heart rate, do increase your body temperature, and so this kind of helps, of course, cool you down. Not very fun, but it does have its purpose, as all of these do.

Alright. That is the function of our sympathetic nervous system, and I will see you guys in our next video. Bye-bye.

Sympathetic Nervous System Example 1

Okay. So for this one, we're looking at why the sympathetic nervous system shunts blood to skeletal muscles. What is the purpose of that? And so, thinking about it conceptually, when we're shunting blood to skeletal muscles, what we're doing is delivering them oxygen. Right? We're delivering oxygen and nutrients like glucose, and those are going to help sustain our muscles if they have to engage in intense physical activity. So looking at our answer choices, it looks like b aligns the best with that. So, to prepare the body for intense physical activity by delivering oxygen and glucose and nutrients to our skeletal muscles. Looking at these other choices here, I see a is to conserve energy, but that's not really what's happening here. Right? Shunting blood to those skeletal muscles is a very effortful activity. We're delivering oxygen. We're delivering glucose. That's not conserving energy. Right? And then c is to facilitate digestion and nutrient absorption, but that's the opposite of what's happening here, right? We are shunting blood away from our digestive system and putting that function on hold in order to deliver all of that oxygen and nutrients to our skeletal muscles. So c is, of course, not happening, and then d would be incorrect based on a and c being incorrect as well. So our answer here is b, to prepare the body for intense physical activity. And there you go.

Why does the sympathetic nervous system cause decreased activity in the digestive tract?

• A. Sympathetic activation stimulates the release of digestive hormones.
• B. Sympathetic activation reduces the sensitivity of the digestive tract.
• C. During sympathetic activation, energy is required elsewhere in the body for more 'essential' functions.
• D. The sympathetic nervous system does not innervate the digestive tract.

Which of the following statements is true?

• A. The sympathetic nervous system increases secretion from digestive glands.
• B. The parasympathetic system causes us to get goosebumps.
• C. Sympathetic tone controls the heart rate when we are at rest.
• D. None of the above are true.

The Sympathetic Subway

Everyone, so this video is going to be a little bit different. Now, we know this chapter can be a bit confusing. There's a lot of new terminology, and a lot of fibers to keep track of. So, we're going to just put the anatomy aside for a second, and we have created an analogy where we're going to be imagining the sympathetic nervous system as like a subway train system. So, hopefully, this helps you kind of just take a step back and just understand conceptually what is happening within this nervous system. So, if we're imagining this as a train system, the nerve impulses are going to be the trains traveling along the tracks, and the tracks are basically nerve fibers. And then our spinal cord is going to be acting as kind of a central terminal where all of our trains are going to be originating from. So, if you look over here at our images, you see we have this kind of subway map here on the left and this very simplified anatomical image here on the right, and you can see in both images that the spinal cord is kind of acting as that central terminal where all of these nerve impulses or trains are going to be starting off from.

Next to that spinal cord, we have a structure called the sympathetic trunk. Now, don't worry about what that is, you'll learn all about it very soon, but for now, just know that it's basically like a parallel track. So, it's going to run parallel to the spinal cord that all of our trains, our nerve impulses, are going to use in some way. So, if we're looking at our images, we have the sympathetic trunk here on our subway map, and then this structure right here is our sympathetic trunk in that anatomical image, and again, it's going to be running parallel to our spinal cord.

Next, we have our ganglia, which are going to be acting as train stations. So, within these train stations, just like with a real train station, these impulses or these trains can either travel straight through them, or we can have a synapse in them. So, imagine you're like either switching trains or like catching a connector train. And I want to quickly draw your attention to this symbol right here, this kind of circle with this triangle next to it. I want you to imagine this as kind of like an axon and a dendrite, and we're going to be using that image to depict a synapse both in this video and in upcoming videos. So, just keep in mind, whenever you see that little triangle with the circle, we're talking about a synapse happening in that location. So, if we look at our maps, we have our little train stations here on our subway map, and then these kind of oval bulbous structures on that sympathetic trunk are the ganglia there. So, all those structures are ganglia. And again, you can imagine if you're on a train and it pulls up to a train station, you could just stay right on that train, and then it's going to keep moving again. That's like if that nerve impulse just passed right through. Or you can have that synapse catch, catching a connector train. So, you're on your train, it pulled up to a train station, you get out, you get on a different train, and then that train heads out. So, either one of those can happen within these locations.

And just as a quick reminder when we're talking about synapses here, we're going to be talking about chemical synapses, which are gaps between neurons that are specialized for communication via neurotransmitter. And if you need a refresher on that, we have a whole video on them in our chapter on nervous tissue. So, feel free to go check that out. And then, finally, we're going to have our effectors which are basically our ultimate destinations. So remember, effectors are just the organs or glands that are affected by the nerve impulse being sent out. So here, our heart, our lungs, our spleen, our liver, those are going to be our effectors, those final destinations that our nerve impulses are trying to travel to. And then one more cool thing to note about our autonomic nervous system is that all of these journeys from the spinal cord have to change trains or synapse one time, which means that every nerve impulse is going to travel through exactly two fibers. So you can see here on our map we have, like, fiber number 1, fiber number 2, fiber number 1, fiber number 2. So keep that in mind because that is a very important feature of our autonomic nervous system, and we see it both in our sympathetic division and in our parasympathetic division. Alright. So hopefully this is helpful as you move through and learn the anatomy in more detail. We're going to keep the color coding as consistent as possible. So the sympathetic trunk will always be yellow, the ganglia will always be green, etc. So, as you move forward, just remember that conceptually this is all that's happening here. We have these trains that are departing from our spinal cord. They're going to travel through that sympathetic trunk. They're going to travel through ganglia at some point, they're going to synapse eventually, travel through those two fibers, and eventually reach their final destination, those effector organs. Alright, so I will see you guys in our next video. Bye bye!

Sympathetic Nervous System Example 2

Okay. So, in the sympathetic nervous system, a ganglion is a place where what happens. So, let's kind of think back to our train metaphor really quick. So, imagine we have this kind of central tract, that's our spinal cord, and that's where all of our trains originate from and our trains are our neural impulses, right? And then in this metaphor, our ganglia act kind of like train stations. So if you have to, for example, change trains or catch a connector train that's going to happen in these ganglia in these like train stations. So, I'm thinking about this more anatomically, we would have an impulse originate in our spinal cord and it's going to travel on a fibre right into that ganglion and then it's going to change trains or synapse there. Right? So that impulse is now going to be carried by a different fibre. So here you can see ganglia are places where neurons can synapse with each other, which is also answer choice c. Looking at these other ones quickly, a reads this is where impulses originate and that's not true they're going to be originating in our spinal cord. Right? And then b says that this is where impulses are integrated, but integrated is not really an accurate word to talk about neural impulses. Integration implies some kind of, like, change or bringing different parts together. That's not really how impulses work, right? They either stop or they continue. It's kind of simple. And then d reads where efferent fibres move fastest through. The wording there is tricky but efferent fibres don't actually move, right? Impulses move through them, so that one would be incorrect. And our answer here is c, this is a location where neurons can synapse, and there you go.

Structure of the Sympathetic Nervous System

Now that we have that analogy in our tool belt, let's go through the structure of our sympathetic nervous system. So we're going to be starting with our spinal cord, that kind of central terminal where all of our fibers originate from, and more specifically our fibers will be arising from between spinal cord segments T1 through L2. That's why this is sometimes also called the thoracolumbar division. And to help myself remember T1 through L2, I like to think of the phrase "tigers lurking," and I like that phrase because it has one word that starts with T, T1, 2 words that start with L, L2, and a lethal tiger lurking is basically guaranteed to turn on your fight or flight response. So think of those lethal tigers lurking. Now, as I mentioned in that previous video, we're going to be working with a structure called the sympathetic trunk, and this is that kind of parallel tract that runs parallel to our spinal cord. And this structure is a bundle of nerve fibers that flanks both sides of the vertebral column. So it's technically one structure, but it runs bilaterally. So you have one trunk on the left and one trunk on the right. And you may hear this referred to as the sympathetic chain or the ganglionic chain, so those all mean the same thing. It's called that because it actually looks kind of like a chain of beads where each individual bead is a sympathetic trunk ganglion. So if we jump down to our image here, you can see on the left we have a slightly more abstract image where we can see that vertebral column laid out very nicely, and you can see how we're working with nerve fibers that arise between spinal cord segments T1 through L2 there. We have these purple and green fibers. I'll explain that color coding in a moment. Then running parallel to our spinal cord, we have that sympathetic trunk, and so each of these circles or beads is going to be a ganglia. And you can see how some of them have our little synapse symbol inside that triangle with the circle. So we're going to see some synapsing happening within that structure. Then we have here some of the major effectors of this division, those kind of ultimate destinations of our nerve impulses. And then here on the right, we have this more anatomical image. So you can see we have our spinal cord there, and then flanking either side of the vertebral column, we have our sympathetic trunk. And then you can see how within that sympathetic trunk we have these kind of bulbous oval structures. Those are going to be our beads or our ganglia. So each of those is a ganglion. Alright. So that's kind of what we're working with so far. Now remember how I mentioned how every nerve impulse has to, like, change trains or synapse one time, and so every nerve impulse will go through 2 neurons, and that's a very unique feature of our autonomic nervous system? So we're going to be calling those 2 neurons the preganglionic fiber and the postganglionic fiber, and the term fiber here is just referring specifically to their axons. And you can see how we have preganglionic here in purple and postganglionic is highlighted in green, and we're going to keep that convention consistent throughout the rest of this chapter both in text and in images, so just keep that in mind. Now, what we often see in this division is that our preganglionic fibers tend to be short and our postganglionic fibers are often long. And I'll explain that whole short and long thing in just one second coming up, but just to kind of reorient you to our image here, you can see we have these preganglionic fibers and preganglionic literally means preganglia or before the ganglia or before the synapses. It is a different way of thinking about that. So we have our preganglionic fiber before the ganglia, and then our postganglionic fiber comes postganglia or after the ganglia, after that synapse. Alright, so that is kind of what we're working with there. Now we have 2 more structures to cover in this video. We're going to be talking about our white ramus communicans and our gray ramus communicans, and before I go over the definitions here, I'm going to jump down to our image and kind of show you where they are. So looking at our anatomical image, you can see we have our white ramus here, and it's literally white because it's myelinated. And then we have our gray ramus here, and I bet you could already guess that this one is not myelinated, so another nice easy naming convention for you. Now what we're looking at here, the structure here, the structure here, those are our spinal nerves. And you guys remember spinal nerves? Those are, of course, nerves that originate from our spinal cord, and they run from our spinal cord out to our effectors, whether those are organs or glands or whatever they are. And so these nerves are going to be basically bundles of axons or fibers. They can be hundreds of axons all bundled together in a sheath. So that is our spinal nerve there, then we have our sympathetic trunk here, and you can see how the white and gray rami basically connect these two structures. So, I'm going to be talking a lot about these preganglionic and postganglionic fibers in this chapter, but please keep in mind that whenever I'm talking about these fibers, they're going to be encapsulated in something. So they'll be encapsulated in a spinal nerve, encapsulated in the white and gray rami, encapsulated in that trunk. So they're always inside of something. So I like to think of the spinal nerves, the white and gray rami, as kind of like tunnels that our fibers actually travel through. So kind of keep that in the back of your head as we go through the rest of our chapter here. So what we see is that our white ramus communicans is going to carry our preganglionic fiber from our spinal nerve to our sympathetic ganglia. Then our gray ramus communicans is going to carry our postganglionic fiber from our ganglia back out to our spinal nerve. So they kind of make like a little loop de loop almost. And I know that it's a very wordy definition here, so I'm going to actually draw it out for you. So I'm going to draw it using purple for our preganglionic fiber and green for our postganglionic fiber. So if we're looking here, we're going to have our purple preganglionic fiber start from our spinal cord and run through our spinal nerve, and then it's going to go through the white ramus and then we'll have that axon terminal there within that sympathetic ganglia. Then our postganglionic neuron is going to have its cell body actually in that ganglia. So we're going the cell body and the dendrite there, and that's how we have that synapse, and then the postganglionic fiber or the axon of that neuron is going to come out through our gray ramus and enter that spinal nerve, and then that spinal nerve will carry it all the way out to its effector organ. Let's just say it's the heart in this example. And then looking at that, you can see how this preganglionic fiber is going to be pretty short, right, because it only has to go from our spinal cord to that sympathetic trunk, and those structures are very close together. So that's why those fibers are often short. And then this postganglionic fiber has to go all the way from the trunk way out to its effector. So that's why those fibers tend to be very long. And if you're looking over at this image and you're like, Hannah, some of those purple ones are looking a little long and some of those green ones are kind of short, you are totally on the right track. There is an exception to this, and we're going to cover that in an upcoming video, so stick around. So that is kind of the basics of the structure of our sympathetic division, and I will see you guys in our upcoming videos to discuss some of this in a bit more detail. So I'll see you there.

Sympathetic Nervous System Example 3

Okay. So, which of the following most accurately describes the pathway for an impulse in the sympathetic nervous system? So, let's just kind of draw it out before we're looking over these answer choices. So we're going to start with the spinal cord. We're going to draw the sympathetic trunk with the sympathetic trunk ganglia and then we'll draw an effector organ. We'll just make it the heart to be fun. Alright. So we're going to have our impulse start in our spinal cord. That is where our impulses originate and then it's going to travel on a fiber to the ganglia. Now that is our preganglionic fiber, right, because it comes before the ganglia. And then that impulse can hitch a ride on this postganglionic fiber, right? Post because it comes after that ganglia and that was where or that is what will deliver that impulse to our effector organ. So looking here, we are starting in the spinal cord. We are then traveling through that preganglionic fiber. We're going to go to that ganglion either passing through it or synapsing through it or synapsing in it like we have here and then we're going to be traveling on that postganglionic fiber and then we'll get to that effector organ. So looking at the answer choices, it looks like b aligns with that perfectly. So our answer here is going to be b. And there you go.

Why are many preganglionic fibers in the sympathetic nervous system short?

• A. Many preganglionic fibers in the sympathetic division synapse at the sympathetic trunk, which is close to the spinal cord.
• B. Many preganglionic fibers cannot carry signals long distances.
• C. Preganglionic fibers carry norepinephrine, which gets diminished over long distances.
• D. None of the above are true.

Efferent neurons in the sympathetic nervous system will always arise in the __________________. Then, they will pass through the sympathetic ____________, where they will either synapse with another neuron, or continue towards the effector and synapse later on.

• A. Spinal cord, trunk.
• B. Spinal cord, fiber.
• C. Trunk, fiber.
• D. Spinal cord, communicans.

Pathways of Sympathetic Innervation

In this video, we're going to be talking about the different pathways of sympathetic innervation. So in our sympathetic division, a preganglionic fiber can synapse with a postganglionic fiber in one of 3 ways. First, it can synapse in a trunk ganglion at the same level, and I'll show you what I mean by "same level" in just one second. We're going to follow along with this blue fiber here. I'm going to highlight it in a nice dark gray as we talk about it. Our preganglionic fiber is going to start in the spinal cord and it is going to travel through the spinal nerve like this. It is going to enter the trunk through the white ramus and then at that same level that it entered, it is going to synapse with a postganglionic fiber, and then that postganglionic fiber will leave through the gray ramus, travel through the spinal nerve, and head out to its effector organ. The preganglionic fiber will enter at that level and then synapse at that same level. That's what I mean by "the same level." Alright. So that's the first method, pretty straightforward.

What we can also have is that the preganglionic fiber and postganglionic fiber will synapse in a trunk ganglion at a lower level or at a higher level. Following along with this red nerve fiber now, we are again going to start in the spinal cord with that preganglionic fiber. It is going to travel through the spinal nerve, enter the trunk through the white ramus, but now it is going to travel down to a lower level trunk ganglion and that is where we are going to have that synapse, and then that postganglionic fiber will exit through the gray ramus, travel through the spinal nerve, and head out to the effector. Basically, that preganglionic fiber will either travel up or it's going to travel down before synapsing in a lower or higher level ganglion. That's the second one. The first and second are pretty similar; we're just talking if they're going to be synapsing at the same or a lower or higher level.

The third one is quite different. For this third one, what's going to be happening is our preganglionic fiber is going to pass through our sympathetic trunk without ever synapsing. It is going to pass through the trunk, and instead, it is going to synapse in what's called a collateral ganglion. So that's what we have depicted right there. Following along with this purple fiber, our preganglionic fiber again will start in the spinal cord like always. It is going to travel through that spinal nerve, enter the trunk through the white ramus, so that's always the same, it is going to travel right on through that sympathetic trunk, never stopping, never synapsing, and head all the way out to this collateral ganglion which will be closer to the effector organ, and then it is going to synapse right in there. Then from there, our postganglionic fiber will head out to the effector. That one is quite different. And when this happens, the preganglionic fiber is actually called a splanchnic nerve, and that is going to be the topic of our next video. So I hope to see you there. Bye-bye.

Sympathetic Nervous System Example 4

Alright. So this one's asking us which of the following statements about pathways of sympathetic innervation is false. So, we're going to, kind of, run through these and draw them as we go just to, kind of, help us visualize it. We're going to draw a spinal cord over here. We'll draw our sympathetic trunk with our ganglia over here. This is not going to be anatomically accurate. I'm just going to kind of visualize what we're talking about. And I'll draw a collateral ganglion over there as well in case we need it later. Alright. So option A reads, a preganglionic and postganglionic neuron can synapse in a trunk ganglion at the same level. So that would look like this: we'd have our impulse happen in that spinal cord, preganglionic fiber going to the same level of the sympathetic trunk, and then a synapse happening right there at that same level. And that's totally possible. Right? So, A is true and A can stay.

Option B reads, a preganglionic and postganglionic neuron can synapse in a trunk ganglion at a higher level. So that would look like this: we have our impulse start in the spinal cord, our preganglionic fiber going to the sympathetic trunk and then traveling up to a higher ganglia. It could also go lower. Right? And then synapsing and then that postganglionic fiber would extend out and that is also possible. So B is true. B can stay.

Option C reads, a preganglionic and postganglionic neuron can synapse in the ventral horn of the spinal cord, and that one's not looking so good. Right? Just think about how these fibers are named. Right? Preganglionic and postganglionic. For them to synapse in the spinal cord, they would both have to exist over here in that preganglionic space. So that doesn't make any sense. So our answer is indeed going to be C. C is false. That cannot happen.

Just to kind of finish out the example here, option D reads a preganglionic and postganglionic neuron can synapse in a collateral ganglion, and that can also happen. Right? So our impulse would start in the spinal cord, that preganglionic fiber would travel through the sympathetic trunk to a collateral ganglia and our synapse would take place there. Right? So our answer here is going to be C is false. These neurons cannot synapse in the spinal cord. And there you go.

A preganglionic fiber arriving at the sympathetic trunk could do any of the following EXCEPT:

• A. Synapsing with a postganglionic fiber at the same level of the sympathetic trunk.
• B. Synapsing with a postganglionic fiber at a different level of the sympathetic trunk.
• C. Pass through the sympathetic trunk without synapsing.
• D. Synapse with a parasympathetic fiber at the same level of the sympathetic trunk.

Splanchnic Nerves and the Adrenal Medulla

Going to finish up this section by talking about those splanchnic nerves as well as the adrenal medulla. As we discussed in our sympathetic division, the preganglionic fibers arise from spinal cord segments T1 through L2. What we find is that from T5 down, the majority of those preganglionic fibers are these splanchnic nerves, which are nerves that synapse in a collateral ganglion rather than in that trunk. So these collateral ganglia are just ganglia that are further out, closer to the effector organs. These nerves basically bypass the sympathetic trunk. They pass through it without ever synapsing and instead synapse in these collateral ganglia. These nerves mainly innervate the visceral structures of our abdomen, such as our stomach, intestines, liver, and spleen. We find that the preganglionic fibers tend to be long, and the postganglionic fibers tend to be short. This is the opposite pattern that we saw in the fibers above T5. So, if we look down here, we have our spinal cord, again working from T5 down with these splanchnic nerves, and you can see how the purple preganglionic fibers must extend all the way from the spinal cord to these collateral ganglia, which are depicted here as yellow balls. They will then synapse in those ganglia, and the now relatively shorter postganglionic fibers go from the collateral ganglia out to the effector. That is the opposite pattern from what we observed above T5.

Next, we are going to switch gears and discuss the adrenal medulla, which is a very important structure for our sympathetic division. To understand why this is so critical, we have to recall something called dual innervation. We have been discussing how our sympathetic nervous system innervates all of these organs, but we haven’t gone into detail about how most organs are actually innervated by both the sympathetic and parasympathetic divisions, which is referred to as dual innervation. However, there are exceptions to that, and one of those exceptions is the adrenal medulla, which is only innervated by our sympathetic nervous system and for a very good reason. The adrenal medulla, when stimulated, secretes epinephrine and norepinephrine, also known as adrenaline and noradrenaline, which are crucial for initiating the fight or flight response. As you can imagine, these are very important for getting your body responsive and active. Thus, this structure is only innervated by our sympathetic nervous system; the parasympathetic division does not want any extra epinephrine or norepinephrine circulating in your body, as that would not aid the rest and digest process. The adrenal medulla, located in the adrenal gland, sits right on top of the kidney, somewhat like a cap. What's fascinating is that it can be considered a modified sympathetic ganglion. Looking at our image, the adrenal medulla is depicted here, showing that it's innervated by just a preganglionic fiber going all the way to this structure, because the synapsing actually happens within the adrenal medulla itself, acting as a modified ganglion. This singular functionality is unique and vitally important for this division because it will be releasing epinephrine and norepinephrine, essential for the fight or flight response.

That concludes our overview of the sympathetic nervous system. Thanks for sticking around, and I'll see you guys in the next one. Bye bye.

Sympathetic Nervous System Example 5

Okay. So collateral ganglia contain which type of cell bodies? Looking here, we have a combination of preganglionic, postganglionic, parasympathetic, and sympathetic. Now, we can very easily eliminate a and b because we're talking about the sympathetic division here. Right? And we'll get to this in an upcoming video, but the parasympathetic division does not use collateral ganglia. It uses something called terminal ganglia. So a little sneak peek for you there. So a and b are out, and we're left with c and d.

Thinking about this conceptually, if we have our spinal cord, we have a collateral ganglia, say, you know, it's way out here, kind of close to the effector organ. Let's just say that it's the heart, for example. Alright. So we're going to have our impulse originate here in the spinal cord. That is the cell body of our preganglionic fiber, right? Where that impulse is being generated. And it's going to come into our collateral ganglia and synapse, which means that that message is being received by the dendrites of the postganglionic neuron inside of this collateral ganglia. So that is where the cell body of our postganglionic fiber is. So, looking at our answer choices, it looks like d would be correct. Our collateral ganglia contain the cell bodies of our postganglionic fibers in our sympathetic division. And there you go.

Which of the following structures would not be innervated by splanchnic nerves?

• A. Liver.
• B. Spleen.
• C. Heart.
• D. Adrenal Medulla.

Here’s what students ask on this topic:

What are the main functions of the sympathetic nervous system?

The sympathetic nervous system (SNS) is responsible for the 'fight or flight' response, which prepares the body to handle stressful or threatening situations. Key functions include increasing heart rate and blood pressure to enhance blood flow to muscles, dilating bronchioles in the lungs for better oxygen intake, and releasing glucose from the liver for energy. The SNS also causes pupil dilation to improve vision, reduces gastrointestinal activity to conserve energy, and stimulates sweat glands to help regulate body temperature. Additionally, it redirects blood flow from the gastrointestinal tract to skeletal muscles, ensuring they receive more oxygen and nutrients during stress.

How does the sympathetic nervous system affect the heart and lungs?

The sympathetic nervous system (SNS) significantly impacts the heart and lungs to prepare the body for 'fight or flight' situations. It increases heart rate and blood pressure, ensuring that blood circulates more rapidly, delivering oxygen and nutrients to muscles more efficiently. In the lungs, the SNS causes bronchioles to dilate, which enhances airflow and oxygen intake. This increased oxygen supply is crucial for sustaining physical activity and responding to stress. These changes collectively ensure that the body can perform optimally under stress or threat.

What is the role of the adrenal medulla in the sympathetic nervous system?

The adrenal medulla plays a crucial role in the sympathetic nervous system (SNS) by releasing the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline) during stress. Located on top of the kidneys, the adrenal medulla acts like a modified sympathetic ganglion. When stimulated by preganglionic fibers, it secretes these hormones directly into the bloodstream. Epinephrine and norepinephrine enhance the 'fight or flight' response by increasing heart rate, blood pressure, and blood glucose levels, and by dilating airways. This hormonal release ensures that the body can respond rapidly and effectively to stressful situations.

What are splanchnic nerves and their function in the sympathetic nervous system?

Splanchnic nerves are a group of nerves in the sympathetic nervous system (SNS) that bypass the sympathetic trunk and synapse in collateral ganglia closer to their target organs. These nerves primarily innervate the visceral organs of the abdomen, such as the stomach, intestines, liver, and spleen. Preganglionic fibers in splanchnic nerves are typically long, extending from the spinal cord to the collateral ganglia, while postganglionic fibers are short, traveling from the ganglia to the effector organs. This arrangement allows for efficient regulation of abdominal organ functions during stress.

How do preganglionic and postganglionic fibers differ in the sympathetic nervous system?

In the sympathetic nervous system (SNS), preganglionic and postganglionic fibers differ in their length and location. Preganglionic fibers originate in the spinal cord (T1 to L2) and are generally short, as they travel to nearby sympathetic ganglia. Postganglionic fibers, on the other hand, are longer because they extend from the ganglia to the target effector organs. This distinction is crucial for the SNS's function, as it allows for rapid transmission of nerve impulses from the central nervous system to various parts of the body, facilitating a quick 'fight or flight' response.