Parasympathetic Nervous System - Video Tutorials & Practice Problems
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Function of the Parasympathetic Nervous System
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In this video, we're gonna be talking about the function of our parasympathetic nervous system. So, just like we did for our sympathetic, I'm gonna go over some of the physiological effects and talk about how it's going to be promoting those rest and digest functions. So, as a reminder, our parasympathetic system is going to be promoting restoration and the conservation of energy. So it's gonna be performing a lot of those kind of homeostatic restful functions. And some of the main examples of parasympathetic effects are going to include decreases in heart rate as well as a constriction of the bronchioles in the lungs. And both of those are going to conserve energy for our body in our gastrointestinal tract, things are gonna get very exciting. We're going to start to see increased movement, increased secretion as well as a relaxation of these sphincters. And that is going to promote food passing through that tract. So a lot of digestion happening there in our um bladder, what we're going to see is a contraction of the smooth muscle as well as a relaxation of the sphincter and combined those are going to promote urination. So, you know, if we're in our fight or flight situation. Urination is not going to be a priority. So that is why that is being handled by our parasympathetic system. And then finally, we're going to see a constriction of the pupil. And the purpose of that is without getting into any eye anatomy in this lecture. When your pupil is constricted, it actually creates a condition in your eye where it optimizes up close vision. So here, you know, we're relaxed, we're calm. We don't have to be scanning the environment for danger or anything like that. So it's going to be promoting vision of objects that are close to you. So this is not an exhaustive list, but these are kind of the main functions of that parasympathetic system and I will see you guys in the next one. Bye bye.
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example
Parasympathetic Nervous System Example 1
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OK. So here we have a list of autonomic effects and we're gonna be filling in for each one if it is the result of the sympathetic or parasympathetic division. All right. So A is increases activity to the gastrointestinal tract and that is going to be parasympathetic, right? Our rest and digest system. So we'll put A P there. All right. So B is vasodilation in skeletal muscles. So that is allowing more blood to get to our muscles, giving them more oxygen, more glucose. And that is a sympathetic response kind of gearing up our body for a potential fight or flight situation and then c dilates pupils. What dilating the pupils does is allow more light to get into them and allows you to see better essentially, which is a sympathetic response. Again, a nice evolutionary mechanism to help us scan the environment for threat or d we have constricting bronchial and that is going to be parasympathetic, right? With our parasympathetic, we're not gearing up to potentially, you know, run somewhere or fight someone. We don't have to be taking in a lot of oxygen and taking deep, deep breaths, right? So that is a parasympathetic and if the parasympathetic is constricting them, we're going to have that opposite effect from our sympathetic dilating them. So, e is going to be a sympathetic effect and then f decreased heart rate that is going to be parasympathetic, right? So we're nice, we're calm, we're relaxed, we're in a state of kind of relaxation and digestion, right? So we don't need to have a really fast heart rate for that. All right. So there you have it and I will see you guys in the next one. Bye bye.
3
concept
Structure of the Parasympathetic Nervous System
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OK. So let's get into the structure of our parasympathetic nervous system. So here fibers are going to be arising from the brain stem and the sacral region. So we're working with the cranial nerves and the sacral nerves. So this is actually sometimes also called our cranial sacral division. And arguably the most important. One of these nerves is our vagus nerve or cranial nerve 10. And this nerve is going to provide about 90% of parasympathetic innervation. So very, very important, they're all doing a great job, they're all important. But this is like the MVP. And then what we find in this division is that many preganglionic fibers actually synapse in ganglia within their target organs. So they're actually synapses within the effector organ rather than in ganglia outside of it. Now, sometimes they do synapse in external ganglia. And in this division, these are called terminal ganglia. So these are ganglia where preganglionic fibers can synapse with postganglionic fibers. And you can think of these as being functionally very, very similar to collateral ganglia. They serve the exact same purpose. It's a location where that synapse can take place. The difference is these terminal ganglia are very, very close to their target organs. So those collateral ganglia are certainly closer compared to that sympathetic trunk, right? But these terminal ganglia are extremely close. So the way I always think of this is, I think of these terminal ganglia as being like that terminal stop or that final stop right before the ultimate destination of that organ because they're just so close to each other. And what we find here um is that the preganglionic fibers are of course very, very long because they're extending all the way from the spinal cord or the brain stem all the way, the way to the effector organs. And then our postganglionic fibers tend to be very, very short. And you can see that here in our image, you can see our purple fibers are all very long and our green fibers are all very short. Again, those synapses are going to be taking place either within the target organs or in terminal ganglia very, very close to them. And you can see that our are arising from the cranial nerves up here as well as the sacral nerves down here. All right. So that is the structure of our parasympathetic nervous system and I will see you guys in our next video. Bye bye.
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example
Parasympathetic Nervous System Example 2
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5
Problem
Problem
In the parasympathetic nervous system, preganglionic fibers are ________ and postganglionic fibers are __________.
A
Short; long.
B
Short; short.
C
Long; short.
D
Long; long.
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