Review of the Sympathetic and Parasympathetic Divisions - Video Tutorials & Practice Problems

Review of the Sympathetic and Parasympathetic Divisions

In this video, we're going to be doing a quick review of our sympathetic and parasympathetic nervous systems by examining the dual innervation of the heart. And as a reminder, dual innervation just refers to the fact that most of our organs are innervated by both the sympathetic and parasympathetic nervous systems. So to kind of orient you to our image here, we've sort of combined the two more abstract images that we've been working with up until this point. So over here on the left, with this kind of yellowish background, we are depicting the parasympathetic innervation of the heart. And here on the right, with this blue background, we are depicting the sympathetic innervation of the heart. So we're going to start here on the sympathetic side and go through and label the anatomy and kind of compare and contrast these two divisions. So as a reminder with our sympathetic um fibers, they're going to be originating from spinal cord segments. T one through L two, those lethal tigers lurking that turn on your fight or flight response, right? And we're gonna have these preganglionic fibers emerging from our spinal cord. And preganglionic just means before the ganglia or before the synapse. And you can see that this is quite a short fiber and that's because it only has to go from the spinal cord to that sympathetic trunk where it's going to synapse within a trunk ganglion. And it will of course, be synapses with these postganglionic fibers. That just means after the ganglia or after the synapse, and then those postganglionic fibers will directly innervate the effector organ. In this case, it is our heart and that sympathetic activity is going to increase our heart rate. Now, as a reminder, not all sympathetic innervation looks quite like this. We can also have those sp plank nick nerves, right. So we did depict that here for you, we have um the innervation of the bladder here as an example. So we have this long spank nick nerve now and that just means that that nerve is going to bypass the sympathetic trunk, it's gonna pass right through it without ever synapses. And instead, it's going to be synapses in one of these collateral ganglia. So it's synapsin within a collateral ganglion. And then we have that short little postganglionic fiber and then we have the innervation of the bladder that way. So remember from about T five down, most of our preganglionic fibers are going to be these blank nick nerves, all right. And then scooching over here to the parasympathetic division. We are starting again with a preganglionic fiber. The big difference here is that these fibers will now be originating from the cranial region, mainly from the brain stem as well as from the sacral region down here. Ok. So we have our preganglionic fiber and you can see it is quite long and that's because the person division does not have any sort of trunk, the way that we see on the sympathetic side. Instead, these preganglionic fibers basically go out almost all the way or all the way to their effectors where they either synapse directly on the effector or in terminal ganglia very, very close to them. So we have these long preganglionic fibers and then these short little post ganglionic fibers. And then of course, this parasympathetic activity is going to decrease the heart rate, we have that rest and digest effect, right. So in terms of similarities, we are always going to have a preganglionic fiber. We're always going to have a post ganglionic fiber. They're going to be um you know, conveying a nerve impulse to an effector. And there's always going to be some type of synapse between those two fibers. Um The big differences are going to be where those fibers originate from. So on our sympathetic side, T one through L two and on our sympathetic side, the cranial and sacral regions will be the kind of origin point. And then the other big difference is really just where they synapse. So again, in our sympathetic division, we're going to be synapses either in the sympathetic trunk ganglia or in those collateral ganglia. And then on the parasympathetic side, we will be synapses in terminal ganglia which are very close to the effectors or directly on the effectors themselves. So those are kind of the big um similarities and differences of these two divisions. And of course, functionally, they have a lot of differences, they're going to be having opposite effects on your organs for the most part. All right. So um that is our review of the sympathetic and parasympathetic nervous systems and I will see you guys in our next video. Bye bye.

Review of the Sympathetic and Parasympathetic Divisions Example 1

OK. So this one asks us, the sympathetic division contains a ganglionic blank where many of its preganglionic fibers synapse. The para synthetic division does not contain a similar structure. Instead, its preganglionic fibers can synapse in a blank gangl. So remember in our sympathetic division, we have that structure that sympathetic or ganglionic trunk that runs parallel to our spinal cord where many of our synapses will take place. So our first blank is going to be the word trunk. So our answer is either going to be B or C based on that. And then in our para synthetic division, we don't have that structure at all right. And instead, we're going to have many of our synapses um taking place in these terminal ganglia very close to the effector organ. So our second blank is terminal and our answer here is going to be B and there you go.