Neural Tissue - Lecture

Ajouté : 2026-05-30

[00:00:02]so this lecture is on a nervous system mainly on nerve tissue we'll start with the overview of nervous system and then we will go into the anatomy of north tissue or nerve cell which is neuron okay let me start the slideshow so so let's go over the nervous system so let's see what what is the nervous system okay so the nervous system is the one of the main system there are two systems in our body of the eleven system one is the nervous system the other is the endocrine system which are called a regulatory system why regulatory because they regulate rest of the system they control or the give commands to rest of the system so that's the reason they are known as a regulatory system a nervous system definitely controls and integrates all bodily activities and that and helps in maintaining life and that is the reason it is considered to be a regulatory system there are many many functions that nervous system controls or I would say all of the functions that is under the influence of the nervous system some of the major function is for the information processing it regulates all physiological functions of the organism it is related with memory conscious unconscious reasoning rationality speech language ability to project ability to make decisions all of this are all part of the nervous system the nervous system has four important functions number one sensory where it gathers information from the external environment number 2 integration which is it processes the information that it receives effector that it produces a response or motor response specially related with muscles and in addition to these three there is another important function of the nervous system which is the internal regulator it is responsible to keep the homeostasis of the body for optimal performance so we will learn the fourth three right here you can see it the three major basic function is the sensory changes that is for example any information that comes into into existence or you know you prick on your finger the information from your finger passes to the to the to the nervous system there it processes the information in here and then passes out the information to have the action in the muscle or trance and we learn all about it so this is a basic or fundamental function of the nervous system how it processes all the information so this is basically an overview of the entire nervous system so I want you to understand this very very well because we'll be using this slide over and over again throughout the entire nervous system and we are learning it so if you the nervous system is divided into two parts number one is the central nervous system called C and and the peripheral nervous system which is called pns so if you look in here this is shown in purple is a central nervous system shown in yellow and you know all of this is part of the peripheral nervous system so if you see in here the central nervous system consists of two major parts one is the brain the other is a spinal cord and the peripheral nervous system consists of all the nerves so it consists of cranial nerves it consists of spinal nerves the cranial nerves come out from the brain and the spinal nerves come out from this final car so there so the entire nervous system is divided into two parts CNS and pns CNS consists of brain and spinal cord pns consists of cranial nerves and spinal nerves that's the basic division of it here is shown a much more advanced division and we will learn as we go along the entire division how different systems work differently so just a little bit more information is is all the information from your body the receptors it can be somatic receptors it can be visceral receptors which are present on the surface of your skin on the surface of the different organs of your body go through the afferent division it's called afferent division starts with the letter A or it is also known as a sensory division which goes into the central nervous system so when I say central nervous system I mean brain and spinal con from there it through the motor division or the efferent division it goes to different parts of the body it is divided again into two parts one is known as a somatic nervous system which controls a skeletal muscle and the autonomic nervous system which controls smooth muscle cardiac muscle and plans okay so as we go along throughout the chapter you will see we are learning more about the complexities and higher level of divisions of the nervous system so as I said this is the brain this is the spinal cord and these are the spinal nerves and you can see the central nervous system which consists of the cranial nerves and the spinal nerves actually operate and connect to the muscle glands and sensory receptors the pns as which are said is divided into two major parts somatic nervous system which is which controls the skeletal muscle and it is voluntary it is under your control the autonomic nervous system which is involuntary which is not under your control is related with the speed of your heart for example if you want your heart to stop right now it's not under your control so the beating of your heart you know how you breathe all of it is part of the autonomic nervous system so now the brain is actually made up of millions or billions of cells and these cells are called neurons now the central nervous system or the peripheral nervous system is made up of two kinds of cell one are call of primary cells which are the neurons as you can see it on the screen the other is it also has supporting cells which are known as Newdow glial cells ok so neurons we are going to start with neurons and then we are going to learn about the neuroglial cells so the neurons are the functional unit of the nervous system what it means is all the functions of the nervous system is done by this cell which is known as the neurons okay it has huge capacity to do action potential and we learn about actual percentage subsequently so basically any impulse transmission of impulse from one neuron to the next neuron to the third neuron is done through the neuron itself so it is able to transmit information and produce an effect and that is one of the major characteristic of electrical transmission is one of the characteristic of our neuron so if you look in here I have another picture in the next slide but if you look in here this is a neuron and in the center you can see there is a single prominent nucleus with a nucleolus and surrounding this structure there is purple colored structure which is called the missile bodies so what are the cell bodies missile bodies are rough endoplasmic reticulum okay in neurons this rough endoplasmic reticulum is called missile bodies think about the function of the rough endoplasmic reticulum you might have learned it in your high school you might have learned it in any other course what is a function of the rack rough endoplasmic reticulum the function of the rough endoplasmic reticulum is protein synthesis it is at the site of protein synthesis so these rough endoplasmic reticulum in the neuron is called the cell bodies and they are responsible for protein synthesis along with it there are neural filaments which are present in here which is basically give it a structure there are microtubules in the cell which also help in the formation of the structure of the cell body okay now I'm going to go over some basic information before we go proceed so the neuron in general is divided into three major parts okay number one the cell body that we just learned then it has two processes one is called dendrites and other is called axon so I want you to understand something is that if you consider this as a neuron suppose this is a neuron okay so this part in here is a cell body these are the processes and this is another process okay so this is the cell body where you can see all the rough endoplasmic reticulum the nucleolus and many other organelles that are present in the cell is present in the cell body similar to that but it has a you know processes that comes out and these processes that come out from the cell body are known as dendrites and there is usually there are many different kinds of neurons but usually the neuron that we are talking about is has one axon that comes out and this is like it looks exactly like this with a cell body with this processes and one axon that comes out of it so so these cell bodies are cell processes are called dendrites and axons okay I want you to understand this well because the function of all each of these parts are different okay the cell body that we just learned on the different organelles that are present the nucleus is present the rough endoplasmic reticulum is present remember it also has multi conned RIA for its powerhouse it has lysosomes it has all the organelle that is present in any other cell except for one which is called the centriole centriole is responsible for cell division and that is not present in neurons as a result neurons do not divide okay so this is a cell body but coming out from the cell bodies are dendrites okay so let's see so this will help us to understand it even better so if you see in here this is the Sun the center the cell body and these are the dendrites so these are these are the dendrites that are coming out and this is the axon okay so as I said if you look in here this cell body has all the organelles except for the Sentry all in it and this is the processing center it processes information the the other processes that are coming out these are the dendrites these actually receive information they take in information and the axon actually transmits the information that it it sends out information so for example if I go to you and talk to you on your ear so my mouth actually becomes the axon and your your actually becomes the dendrite why because your ear is receiving information and my mouth is delivering information so when it's the delivering information is done by the axon and the receiving end is the dendrites okay apart from that you can see da da let's go over the dendrites first you can see the dendrites have the dendrites have several branching right and these branching are called spines and they take in information and then if you go further down in the cell body you can see the nucleus nucleolus the cell body is called soma it is called very carrion and cell body so it has many names inside the cell body there are missile stains structure which are known as missile bodies there are micro filaments in these around in the cell body which gives the neuron a neuronal cell body and these microfilaments are very very important because the alignment they are in a particular alignment and when this alignment is in a disarray it can lead to many diseases and one of the disease which I'm pretty sure all of you know is alzheimers disease which leads to you know this array of the microfilament so the cell body in addition has mitochondria lysosome smooth endoplasmic reticulum all the organelles that are in this in any other cell is present in there I want you to in addition understand that the the point the point where the ads on comes out is called the axon okay it is very important to remember this region because it is called a trigger zone and when we learned about the action potential you will see the importance of this region this is the trigger zone which is called the action axon hillock and from there comes out the axon okay the axon is usually myelinated that means it is covered like a blanket around it is there is a blanket around it which is basically a lipid layer which is called the myelin sheet okay so these are the myelin sheet covering the the axon the myelin sheet is not continuous there are gaps in between them and these gaps are known as the nodes of ranvier and these and the axon further ends into the axonal terminal there are synaptic knobs you can see these small knobs these synaptic knobs are also very important because they carry synaptic vesicles what are these synaptic vesicles the synaptic circles are round structure which carry neurotransmitters which are required for nerve transmission so next few slides is going to be just a review of what we have learned right now so you can see we are talking about dendrites how it conducts or receives conducts impulse towards the cell body that it takes in information usually it's short it's highly branched and it is not myelinated is this unmyelinated so if these are the dendritic branching are also known as dendritic spines this is axon as I said that this comes out at a point from which it comes out is known as the axon hillock and it conducts the impulse away from the body it is covered by the myelin sheet as you can see it in here and these myelin sheets are made by a cell or I would say the Neo neuroglial cells which we will learn subsequently made these oligodendrocyte and those cells are called oligodendrocytes which we will learn later on and then these axon actually ends up into the synaptic knob they are also known as axonal ending on axonal norm and these swellings carry synaptic vesicle neurotransmitters which are important for Northern Pass okay so this picture actually it shows you how a neuron is sending a releasing neurotransmitter to another one in order to send the impulse from one neuron to the next so if you see this picture you'll understand it better one neuron is carrying an impulse and sending that impulse to the next neuron many many such neurons are involved in the entire process and this process by which it releases the neurotransmitter into the and the next neuron the process is basically called synapse and the the neuron that sends the or releases the neurotransmitter is known as the presynaptic neuron and the neuron that receives that and those neurotransmitters have receptors on the surface of it and these are neurotransmitter receptors present once the neurotransmitter is released these receptor take in the orchid the neurotransmitters get attached to these receptors and the process continues so there is a chain of events that take place in the postsynaptic neuron for the next neuron and the process goes on from one neuron to the next neuron and so on and I think we have a separate section which we will be learning more about synapse later on okay so the myelin sheath as I was saying these are the axons and it is wrapped by a lipid layer which is called the myelin sheet okay the myelin sheaths are made by the cell this is called oligodendrocytes and these oligodendrocytes are present in the CNS and there is another nerve cell which are known as the Swan cells which are present in the p NS which is responsible for making this myelin sheet in the peripheral nervous system neurons of the peripheral nervous system okay so as I said these are Swan cells of the pianist Swan cells that myelin ate and wrap the neurons of the pianist you can see there is these lipid layers are formed which are called the myelin sheet and together the entire thing is known as new which is very very important these mining sheets are responsible to increase the nerve transmission and without these because we do have unmyelinated neurons also in the nervous system but the transmission of impulse in those neurons is very very slow so how does the transfer take place in the axon so we have to understand that the axon I'm going to go back one one one slide so that I can make this point clear so if you look at here this is the cell body and this is the axon so information needs to travel from the axon from the axon to the synaptic terminal so when it moves from the cell body to the synaptic terminal it's known as anterograde when the information or any material or chemicals or any substance moves from the axonal end to the cell body it's known as retrograde ok so going back to the same slide that we were talking about so if you look at here there are two transmission that take place one is known as anterograde that is movement of from the cell body to the synaptic terminal and if this task is done by a protein which is known as heinessen okay so they have footlight structure they carry those neurotransmitters or proteins from the cell body that it's made and then travel to the axonal terminal this is the main way the transport usually take place from the cell body these proteins the neurotransmitters these chemicals are processed they are made and they travel from the cell body to the axonal terminal but there are there is a way sometimes from the adze terminal it goes back to the cell body and that is done by another protein which is known as that name there are some examples of it one is there are certain toxins certain bacteria or viruses that can move from the axonal terminal to the cell body where they can be either killed or they can you know accelerate so it depends upon on the infection functionally neurons can be divided into three major parts number one sensory neuron motor neurons and inter neurons sensory neuron are also known as afferent neuron they travel the transmitted information from the skin in the muscle joined organ sense organs visceral organs to the central nervous system so again when I say central nervous system I mean brain and spinal cord and then it is processed there in the brain and spinal cord it is processed there a very good example would be think of a situation when you are taking you want to mail some someone a card okay it's Christmastime or it can be any other occasion you want to send holiday greetings to your friends so you are taking some letters to be mailed to many different places of the country one may be Albany that may be Minnesota thought maybe Canada doesn't matter anywhere and there is another of one of your friends they are also springing in different types of letters to the main post office to be distributed to different places so once all these letters and cards come to the main problem Ain mail in a post office they process it they say okay X number of mail is going to Albany Y number of is going to maybe Detroit Z number of vans are going to San Francisco and you know different X number is again going to New York and they process it and then they they execute it it might be through a plane it can be through walking it can be through a truck they deliver it to different parts for its execution same thing in here these are sensory neurons these letters that you are bringing in are the sensory neuron where are you taking it you're taking it to the main office and that's where the brain and the spinal cord comes into the picture the processing that takes place is done by the inter neurons which are present in the brain and the spinal cord there are 90% of these neurons are inter neurons and once they have been sorted out then they are delivered back to the corresponding what are the effectors it goes to the houses where he wanted to send those letters so these are done by the motor neurons motor neurons send in information for its execution maybe you know for example you you want your must you want to pick up some some object the spitting of the last part is done by the motor neuron by the skeletal muscle so information gets in it gets processed and then it gets executed structurally and the neurons can be actually divided into four major parts ok first is a multipolar neuron and the one that we were just speaking about is multipolar where there is one a cell body several then rides and one axon that comes out ok so this is the multipolar and most of the neurons the CNS and pianist are multiple neurons bipolar neurons is one main dendrite there is one main dendrite and one main axon and the cell body is in the center ok it's found in the red in the year sensory organs it's found me unipolar neurons unipolar neurons is basically pseudo bipolar neurons that is the cell body basically of the bipolar when it's pushed to one side it basically looks like they will be polar neurons okay this is a very important kind because they use unipolar neuron on the sensory neuron in the CNS and see the pianist mainly pianist okay so if it will lower when we learn a spinal cord you will see how the cell bodies flock at one end so these unipolar neurons have a cell body at one end and then there is axons and the dendrites on one end so it looks very different but it is very similar to the bipolar neurons but the cell body is in the center and it basically pushes out the cell body if you look like a unipolar neuron axons onic apparently there is no axon or I would say it is very difficult to know which is an axon and which is a dendrite in this case okay so for different kinds of to be wrong based on their structure number one multipolar bipolar unipolar and an axon ik according to their function there are three different kind sensory neuron motor neurons and Association or inter neurons