Nervous System- Spinal Cord

Added: 2026-05-27

[00:00:00]hi this is Professor Chakraborty this is the lecture on spinal cord spinal reflexes and spinal movements we will be learning about the spinal cord anatomy first and then we'll go into the spinal reflexes and spinal movement the spinal cord ranges about 45 centimeters in length it goes straight down from the medulla oblongata and ends in the final filum terminale so let's go to the next slide so if you see in here this is the medulla oblongata and it's slide straight down and ends into final filum terminale now the spinal cord if you see the spinal cord that is shown in the slide has five different parts starting from the top to the bottom is the cervical plant which is a superior moose it's a little top of the spinal cord it continues from others medulla oblongata so it continues from here so this part is the cervical rod and the nerves or the spinal nerves that come out from there is known as the cervical spinal norm next comes the thoracic spinal nerves which is this region in here which the nerves that come out from this region is known as thoracic spinal nerve then comes the next part which is called the lumbar region which the spinal nerves that come out from this region is known as lumber spinal nerves and then comes the sacral part and then the oxygen part the spinal cord actually starts from the middle of nagato it goes parallel to certain distance and then tappers off so it tapers off around the region which is known as the conus medullaris Tattersall and this is the region about l1 and l2 of the vertebra this is actually considered to be the official end of the spinal cord after the that region basically there are branches of that comes out of the spinal cord and the end of it is called the final terminal which is nothing but the PIA mater so if you remember pear matter these and meninges that we have learned in the brain the dura mater arachnoid mater and the PIA mater this is the innermost layer the PIA mater which is basically this final terminal the other important structure to remember is you will see this region in here which is called a corner equator harder the word cada means tail equalist means equals means horse so at this point there is branch chain that starts from here and that's the region it looks like a pony tail that women or girls make in there you know with their hair it branches off and that's the reason it's known as cada equator this region in here so if you look at the different cross sections of this region you will see that this is for the cervical this is the thoracic region this is a lumbar sacral and so on each of these region have some common structure but in addition to that it has some specific structure in this lecture we will be dealing with the general structure of the spinal column the spinal cord is associated with 31 pairs of spinal nerves these spinal nerves that we just spoke about these are the cervical spinal nerve thoracic lumbar sacral and coccygeal nerve these are the nerves there are 31 pairs meaning these are pairs of nerves that come out from the left and right side of the body and which control the different the peripheral parts of your body as well as the entire it controls the entire parts it brings in information it brings out information these final nerves are mixed nerves so what does mixed nerve mean mix no means that they have both the sensory and the motor neurons and their sensory axons that release nerve signals from the receptors to the spinal cord and a motor neurone new axons that conduct nerve signals from the spinal cord to the effectors which is mainly muscle and glands so so if you if you look at the the protection of this one and God just like the the brain the spinal cord also is protected the spinal cord protection has three again it is surrounded by the vertebrae vertebral column so that's the first line of protection and in addition to that it also has meninges three layers of manages dura mater erectile mater and the PIA mater so three layers dura mater electron mater and Pia mater and in addition to that there are spaces or gaps in between them so if I have to go let you know about the different layers that are present including the spaces is as from outside to inside is vertebrae is a first then epidural space then dura mater then subdural space a deployed mater some arachnoid space and finally the Pia mater so if you look in here you will see these are the different layers starting with the vertebrae and this is a Pia mater in here so first and foremost is the vertebrae then there is epidural space epidural space is the space between the dura mater and inner walls of the vertebrae and it has a ton of connective tissue blood vessels and most issue etc epidural anesthetics that are given to lessen the pain during childbirth is introduced in this space it's called a epidural epidural it is called the epidural anesthetics that are given into this space in order to reduce pain in addition next comes the space known as the subarachnoid space as you can see in here the subarachnoid space so continuing with the Benin Jesus so there is direct noid matter as you can see it in here and which leads into the subarachnoid space and the summer of night space is where it is filled with cerebrospinal fluid which is CSF and then comes the last layer which is the Pia mater okay so just going back to what we have studied so far in its review this once more so okay so the spinal cord starts from and the medulla oblongata Goes Down till the l1 it happens at l1 and l2 of the vertebra which is basically called the conus medullaris and at one point it branches which is known as corner equator and the branching and ultimately tappers off at one point which is known as a random terminal there are spinal nerves that come out of the spinal cord the spinal cord is divided into five sections cervical thoracic and lumbar sacral and coccygeal cervical spinal nerves come out of the spinal cervical region thoracic spinal nerves from the Masek region lumbar spinal nerves from the lumbar region sacral spinal nerve from the sacral region and coccygeal spinal nerve there are 31 pairs in all total pairs of spinal nerves that come out of the spinal cord if we make a cross-section of the different parts of our different sections of this mannequin it is visible that there is a general structure that the spinal cord follows from each of these region apart from that there are two regions which are called the cervical enlargement and the lumbosacral enlargement these are and parts of the spinal cord that control the upper and the lower limbs since the number of spinal nerves required in these regions are larger there are newer nerves there is a bulk of them present in these regions that furnish the upper region and the lower region and these are known as the cervical enlargement located in the inferior of the cervical part of the spinal cord and contains neurons that innervate the upper limbs and the lumbosacral enlargement also known as the lumbar enlargement extends through the mid lumbar part of the spinal cord and hinder innervates the lower limbs so going next regarding the protection we have the vertebral column as the first line of protection and then there are meninges manages are nothing but connective tissue covering we have three layers of manages dura mater and at Nan Madol and Pia mater apart from that there are spaces there are spaces which are filled generally with the CSF cerebrospinal fluid which is also a line of protection for the spinal cord so going from outside to inside then vertebra epidural space dura mater subdural space and annoyed battle subarachnoid space and finally the P an adder now let's understand the so this is the next slide actually shows you all of the different managers that we just spoke about so now let's understand and the anatomy of the spinal cord so you can see in this slide there are two regions white color and there is a great color region so just going back to what we have learned before when were learning about brain that there are white matter and there are gray matter white matter are mainly myelinated axons and gray matter are generally cell bodies and unmyelinated axons okay so keeping that in mind if we look at the spinal cord you can see that a cross-section shows you that the cremator is h shaped or butterfly shaped and comedy and it has pointy structures at four regions okay the spinal cord in total is if you make it a cross-section if you look at the cross section has an anterior view which is the silly there is this region here and a posterior view which is this region in here in the anterior view or as anterior part of the spinal cord there is a groove so you can see this deep groove that you can see and this is called the anterior median fissure and the posterior part has 40 posterior median sulcus because the group is much shallower so the starting with the great power to gray matters that is present inside the in the spinal cord the cremator has horns there are anterior horns you can see these are the anterior ons there are posterior haunts and there are lateral haunts the Han River haunts basically in houses cell bodies or somatic motor neurons which innervate the skeletal muscle so you can see the somatic motor as it's written here so it has neurons that come out from these regions and go to those skeletal muscles the lateral horn are mainly the lateral horn in here is mainly cell bodies of the autonomic motor neurons autonomic motor neurons are we will learn that in in next in our next lecture the autonomic nervous system which is mainly means those organs apart which are not under your control basically like heart muscle smooth muscles and glands beating of the heart controlling heart muscle contraction and relaxation those are all part of the autonomic system and those are the neurons innervate into those the cardiac muscle smooth muscles under plants the posterior honge which is this in here are mainly carry axons of sensory neurons and cell body of inter neurons sensory neurons that bring in information sorry verdad bring in information to the spinal cord in addition to that you will see in the center there is a central canal this hole of the central canal is filled with cerebrospinal fluid and around this region around the central canal is called the Great Commission the part which is anterior part of it is known as anterior commissure and the posterior part is called the posterior graeca measure the Kamisha primarily country contains unmyelinated axons and it serves as a communication between the left and the right side of the gray matter the white matter very important and we will be learning more about the white matter when we go into the spinal movement the smile the white matter of the spinal cord is external to the gray matter as you can see it in here this is a white matter and these are called white matter because they contain myelinated iran's the white matter of each side of the cord is partitioned into three regions and these are called funiculus fullness means called so funiculus is the plural of it so these are these are sections this is the anterior funiculus or anterior white column this is the posterior white column and this is the lateral white column the these axons within each of these white car white matter funiculus are organized into smaller structural units called tracts so within the white column or you can say white funiculus there are tracks what attracts tracts are bundles of neuron that have a common unknown origin and destination so we will be talking about these tracks again so just reminding you so these are tracks again these are these are white columns they are made up of myelinated neurons and these white matter are white columns are also called funiculus these can be partitioned orbits these had organized into smaller units smaller structural units called tracks these tracks are basically group of neurons that have a common origin and destination so this is this slide is pretty much they have learned that before in in the medieval learning brain and according to the the neuronal structure they there are sensory neuron motor neurons and inter neurons sensory neurons bring in information to the spinal cord motor neuron distribute commands to the peripheral effectors which is mainly muscles and glands and inter neurons are present within the spinal cord that interpret into information and coordinate responses so this is the classification based on the function we have learned how neurons can be classified according to the structure which is unipolar bipolar multipolar and axial axial Janek so here again so according to structure the neurons can be divided into three parts sensory neurons that bring in information to the spinal cord motor neurons that distribute the commands to the peripheral effectors interneuron which is present in the spinal cord that work that interpret and pollinate responses so according to structure structurally they can be divided as unipolar or bipolar multiple learn and axis unit but we are going to focus mainly on the unipolar neurons because those are the ones which are responsible which to bring in information to the spinal cord and of course there are motor neurons and take information and into neurons that are present in this mannequin so before we go into a little bit of how information comes to the spinal cord let's understand the spinal nerves so we learned before that there are 31 pairs of spinal nerves that come out of the spine alone or bring in information and bring out information from the spinal cord these are called spinal nerves these are mixed neurons because they have both sensory and motor neurons in them which I'll show it to you in the subsequent slide so here we are learning about the structure of the spinal now if you have taken anatomy and physiology you might remember the organization of the muscles or how muscles are made it's exactly the same a the spinal nerves are made exactly this way so if you look in this slide you will see this is a neuron and it is marinated and it has an outer covering a connective tissue covering which is known as endothelium many such neurons are axons together form what is called a fascicle a fascicle is colored by another connective tissue covering which is known as perineurium and many such very Nubian joined together to form what is called a nerve and that is covered by the outer layer covering which is known as epithelium again axon this is a neuron neuron covered by a connective tissue covering which is known as Antonio many such neurons together or axons together form fascicle which is covered by peri Nerium and many such fascicles together form the muscle and form I'm sorry the nerve the nerve has an outer covering which is known as the epithelium as you can see it in here there are blood vessels across in the in the in the in the north and which is extremely important because it is made up of cells neurons and cells have to function and for that they need oxygen and nutrients and remove face material so the peripheral and the spinal distribution of the nerves is shown in the subsequent three two slides and I'm going to divide it into two parts number one how information comes to the spinal cord to the sensory neuron and the other is how information is distributed from this final final goal so as you can see it in here one very very important structure is shown in here which we did not learn purposefully when we were learning the structure of the spinal cord because it's outside of the spinal cord is this is called the dorsal root ganglion so if you remember these as I said that the neurons that bring in information are the sensory neuron and they are unipolar neuron so please review the the information that we had learned in trade regarding unipolar bipolar mixed neurons these unipolar neurons have the cell body popped out of the axon so you can see the cell bodies are outside of the axon so the cell body remains outside of the spinal cord it's a group of such cell bodies that remain outside and only the axon moves inside the spinal cord to do the function to deliver the information these group of cell bodies together is known as dorsal root can be on so these are sensory neuron bring in information it is integrated in here and processed in here by the inter neurons and then they pass out to the ventral root or through the motor neurons and is distributed to the whole body which I will show to you in the next slide so again through different receptors as you can see sensory neurons are bringing in information to the spinal cord it gets processed in here and then through the ventral lude it does its action so if you look into the next line you will understand what I'm saying that this is a spinal nerve which is bringing in information from the different parts of your body through the sensory neurons the cell bodies remain outside which is known as the dorsal root ganglion it brings information to the spinal cord it is processed here and then through the ventral root so now the we are talking about the motor neurons now so if you can if you look in here these motor neurons take out the information and then distribute you through the several through the motor neurons is distributed to each and every peripheral part of your body so when the information comes in it is known as the dorsal root when it goes out it's known as the ventral root but remember this is the spinal nerve and the spinal nerve contains both the sensory neuron and the motor neurons and hence the spinal nerve is called a mixed nerve which we learned before so this is basically an overall anatomy and partially the function of the spinal cord