 Sympathetic nervous response. Let's look at the anatomy of the sympathetic nervous system. What are some things that you notice right away from this drawing, what we've already done? Anatomically speaking, the sympathetic nervous system has some characteristics that are kind of bizarre. First of all, our ganglion in the sympathetic nervous system is close to the spinal cord. That's because do you notice that my preganglionic neuron is short? What does that mean about my ganglionic neuron? These things are long. That's an enormous and obvious anatomical difference between a sympathetic pathway and a parasympathetic pathway. There's something else that you notice. Holy branching preganglionic neuron. Look at this thing. The preganglionic neuron, its axon, actually branches out and heads in many different directions. Think about that. Your sympathetic nervous response is a holy bear coming straight at me. I better do something, I better run away quick. The quicker you can get the information out there, the more efficient you're going to be, the more likely you are to activate the number of pathways that you need to activate to effectively get away from the bear. One way to do that is activate one neuron. Here's my one neuron. My one ganglionic, I mean preganglionic neuron, is cell body was member in the lateral gray horn. Just tell one of those guys, hey, there's a bear over there, let's do something about this, and that one is now going to, it's the phone tree. It's the pyramid scheme. That one is calling like 50 others. And now 50 of them, 50 ganglionic neurons have been activated and all of them are sending out their message to the effectors saying bear, run, or hug, bear's got a hug, it's a bear hug. Aww. So the branching aspect of the preganglionic neurons is something you're not going to see in the parasympathetic nervous system. Can you defend the functional consequences of this structural setup? Oh my gosh, I hope I remember because that's a phenomenal exam question. What else? Not only, okay, we've got our differences here. Now let's go map it on to a spinal cord because now we're going to notice that there's some interesting stuff going on in the parasympathetic nervous system that we're not going to see anywhere else. And remind yourself, where is the sympathetic nervous system? Remember, it was T1 to L2. So if we took a slice of spinal cord at that level, this is what we're going to see. Well, don't look at this yet, but I'll bring you back to that and show you what that one means. Here's the Wendy-style version first. Got to do a Wendy-style first. Does it look familiar? Of course it does. We can map everything onto our spinal cord and I am going to resist the urge to do like a giant review and map everything onto the spinal cord and instead I will focus and just map my sympathetic fibers onto this spinal cord. Where are my cell bodies of my sympathetic neurons? Of my pre-ganglionic sympathetic neurons. Where are those cell bodies? I hope you just answered me. Right there in the lateral gray horn. Where does my axon travel? Absolutely. Out through the anterior gray horn. Out through the anterior root. Out through, where am I now? Spinal nerve. And it's actually going to hit it. Now, what do you see that's different? What the heck is this little boobly doodly woo? Nobody knows. But guess what? It's an off ramp. It's an off ramp that, look, my pre-ganglionic fiber is going to take that off ramp. It does. It actually enters the anterior ramus and then this little off ramp comes off of the anterior ramus at T1 to L2. And then what is the little bobble here? You know that's the ganglion pounds, right? It is. Doesn't it look just like my posterior root ganglion? It's a ganglion. It's my autonomic ganglion. It's my sympathetic ganglion. And it makes me a little bit excited. I'm going to change my color just a little bit just so you can see. Can you see the difference between my greens? I want you to be able to see it because now we're synapsing on my sympathetic ganglion and that neuron is going to re-enter the anterior ramus and then it's going to head out and do its thing out. Who? Who's it going to affect her? Because I love you. It's going to affect her, your heart. It's going to affect. It's going to innervate your heart and it's going to dump neurotransmitter, right? You can't see that at all, but yellow is my favorite color. Okay, we'll make it orange. There. That's the worst color I've ever picked ever. Sorry, doesn't mean that I don't love you. Here's my post, here's my ganglionic neuron. My ganglionic neuron in sympathetic nervous system is long. It innervates the heart, it increases heart rate. It doesn't really impact, but this is the weird part. This is the piece that is different. These are called the rami communicons and that, remember, this was the anterior ramus. These are the rami communicons. Rami, maybe like branch, spinal nerve, rami communicons, rami communicons, spinal nerve. The anterior ramus and heading to my effector. Does it make perfect sense? But of course, let's draw what else do we have that's true. I feel like I've drawn this before, but I don't know if I did. Remember that my ganglionic neuron is, excuse me, my pre-ganglionic neuron is myelinated. My ganglionic neuron is not myelinated. Does it make you happy? I think it's good. Oh, I know what I want to show you. I want to show you a real picture. I'm not showing you one of the characteristics that I really wanted to show you, which is the branching. I'm not showing you the branching because actually these structures right here go up and down just like the spinal cord goes up and down. So look, there's a really cool visual in your book that shows you, oh, let's look at this one right here. Here's my spinal cord, here's posterior, here's the anterior, here it comes, the information is coming in, travels through the anterior ramus off into these little rami communicons, the sympathetic ganglia, the sympathetic ganglia that are tight to the spinal cord, and then we can have massive amounts of branching, we can spread fibers all over the place, we can go up, we can go down, and communicate all over the place in here, and then we synapse with our ganglionic neuron, which ultimately goes out and deals with the effector. It's easy, isn't it? You want to see how the parasympathetic system has different anatomy. What's one thing that you already know that will be different about the parasympathetic nervous system? Where's the slice taken? This slice of spinal cord is taken somewhere between T1 and L2. If we're outside of that range, we're going to have a different anatomy. Okay, I'm going to come back and tell you about the parasympathetic nervous system.