Med-Surg - Nervous System, part 3: A&P Review - Spinal Cord, Meninges, ANS
by Cathy Parkes October 27, 2021 Updated: December 29, 2021 4 min read
Hi, I'm Cathy, with Level Up RN. In this video, I am going to continue my anatomy and physiology review of the nervous system. Specifically, I will be talking about the spinal cord, the meninges, as well as the autonomic nervous system. At the end of the video, I'm going to give you guys a little quiz to test your knowledge of some of the key facts I'll be covering in this video. So definitely stay tuned for that. And if you have our medical-surgical nursing flashcards available at Level Up RN, definitely pull those out so you can follow along with me.
First up, let's talk about the spinal cord, which is comprised of bundles of nerve tissue.
So the spinal cord is essential for motor function, for regulating organ function, for processing sensory information, and for transmitting signals between the central nervous system and the peripheral nervous system.
So the spinal cord connects into the brain stem and it runs down the spinal column, terminating around L1 or L2.
So if we need to do a lumbar puncture for the patient, we need to go below that. So lumbar punctures are typically done between L3 and L4, or L4 and L5.
So surrounding the brain and the spinal cord, are the meninges, which is a membrane that's composed of three different layers.So we have the dura mater, the arachnoid mater, and the pia mater.
So I tried to think of a good way for you to remember those layers in order from the outside in, so DAP. I thought about DAP. Okay, so DAP's not really a word. I thought about DAP, you know, and maybe me being ridiculous, and dapping will help you remember these layers. It's not DAB, by the way. It's DAP.
So in addition to knowing those layers from top to bottom, I want you to think about the spaces between those layers.
So in between the skull or the vertebrae and the dura mater, we have the epidural space. So epi means upon. And dural. So above the dura mater is that space where we can provide the patient with epidural analgesia or epidural anesthesia.That's also a space where we may end up with a hematoma when a patient has a traumatic brain injury. So we'll talk more about epidural hematomas when we talk about T BIs.
And then, below that, we have the space between the dura mater and the arachnoid mater, and this is the subdural space. So sub means under. So subdural means under the dura mater. And again, with a traumatic brain injury, or TBI, we can end up with a hematoma in this space. So that would be a subdural hematoma.
And then the space between the arachnoid mater and the pia mater is the subarachnoid space. So under the arachnoid layer and in this space, we have cerebral spinal fluid that circulates. So cerebral spinal fluid, or CSF. It helps to surround and cushion the central nervous system. It also provides nutrients and eliminates waste products from the nervous system.
Next, let's talk about the autonomic nervous system, which, as I mentioned in my first video in this playlist, is part of the peripheral nervous system.
So the autonomic nervous system helps to maintain homeostasis in the body by innervating smooth muscle, cardiac muscle, as well as a number of glands in the body.
So within the autonomic nervous system, we have the sympathetic nervous system and the parasympathetic nervous system.
So the sympathetic nervous system is responsible for controlling the body's fight-or-flight response. And nerves of the sympathetic nervous system originate between T1 and L2 in the spinal cord. So this is kind of important to remember because when we talk about spinal cord injury, depending on where the level of injury is, it can definitely impact sympathetic nervous system function.
So when the sympathetic nervous system is activated, this causes an increase in cardiac output. It causes vasoconstriction, which increases blood pressure. It also causes bronchodilation, as well as pupil dilation, and then it decreases secretions and peristalsis.
With the parasympathetic nervous system, this controls the body's rest and digest response. So nerves associated with the parasympathetic nervous system originate between S2 and S4 in the spinal cord.
Activation of the parasympathetic nervous system results in decreased cardiac output, vasodilation, which decreases blood pressure. It also causes bronchoconstriction and pupil constriction. And then it increases secretions and peristalsis, which makes sense, right? Since this is the rest-and-digest response, that we need increased peristalsis and increased secretion.
All right, it's time for a quiz. I have three questions for you. First question. What do you call the space between the vertebrae and the dura mater? The answer is the epidural space. Question number two. Activation of the sympathetic nervous system causes bronchoconstriction. True or false? The answer is false. It causes bronchodilation. Question number three. Activation of the parasympathetic nervous system results in increased secretions and increased peristalsis. True or false? The answer is true.
Okay. I hope you enjoyed that quiz and this video. If so, be sure to like the video and leave me a comment because I always love to hear from people who watch my videos. Take care and good luck with studying.
So I'm going to be talking about the eye and the ears. The eye, so there's two of them. [laughter] We're only going to talk about one of the eyes. Okay. Right. We're going to talk about both eyes. I just need to say that, right? Okay.
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