welcome to manna-fest publishers welcome Lana's for today's biology lesson the topic is reception response and coordination in animals so the previous lesson we introduced irritability in animals we learnt about the nervous system we also talked about the endocrine system and the various parts that are involved so today we shall continue the same whereby we shall learn about the structure and function of the na cells so when you talk of the structure and function of the nerve cells it's worth mentioning that a nerve cell is the basic unit of a nervous system is the smallest unit of a nervous system and enough cell so Lunas a neuron is a specialized cell is a specialized cell modified for transmission of nerve impulses modified for transmission of nerve impulses which are electrical in nature so we can start by saying that enough cell also known as a neuron is the basic or is the smallest unit of a nervous system is the basic unit of a nervous system we can also say that a neuron which is also the same as than a cell is a cell modified for the transmission of electrical impulses that means electrical messages electrical impulses from one point to another from one point to another within the Nava system so just to recap a bit enough cell is also known as a neuron and it's the basic unit of a nervous system is the smallest unit of a nervous system and we have said that a neuron is a cell that is modified for the transmission of electrical impulses from one point to another within the nervous system so now we are going to look at the parts of an AR cell then our cell and we'll simplify it a bit that so we have a general structure of an arson is a general a general structure of a nerve cell which we are also calling a neuron it has a number of parts and we are going to label the parts there is the part that is here that looks like a head which is now the equivalent of a cell we refer to it as a cell body is now the equivalent of a cell which is the cell body and of course that cell body has a nucleus a cell body containing the nucleus then that cell body also has some extensions we call those extensions dendrites we refer to those extensions as dendrites then there is the main filament that projects from the cell body we refer to that as the axon then from the axon we have this part that surrounds the axon and we refer to it as the myelin sheath we shall look at it in more details then we have a certain cell here that is next to the myelin sheath we refer to it as the Schwann cell is the Schwann cell and then we also have at the end what we call the terminal dendrites the dendrites at the end the terminal dendrites yeah we have it like that I think we have labeled more or less all the parts that make the general structure of an ourselves now I want us to ask ourselves one question why is this nerve cell elongated why is it long why is it long it is elongated to enable transmission of nerve impulses that's why it's a long cell so that's what we are saying it is modified for the transmission of electrical impulses within the nervous system now we will look at now those various parts that constitute the nerve cell and of course their functions so parts of a nerve cell or parts of a neuron the first part that we shall start with is the cell body which is the equivalent of a cell the cell body and we can say that cell body contains the nucleus contains the nucleus that contains genetic material that contains genetic material so the genetic material is found within the nucleus the nucleus is found within the cell body now outside the nucleus we have the cytoplasm and that cytoplasm extends into the ad zone and when it extends into the axon we refer to it as the acts of plasm the cytoplasm located within the ad zone is called AXA plasm so let's first of all mention the axon and this is the main projection from the cell body is the main one is the main projection from the cell body number three number three there is this myelin sheath that surrounds the axon we have the myelin sheath and we can see that this is a fatty layer is a fatty layer or is a fatty sheath that insulates that insulates the axon it covers the ad zone it insulates the axon and propagates transmission of nerve impulses then number four we have the Schwann cell the Schwann cell Schwann cell is one word and this is the one that secrets the myelin sheath is the one that produces the myelin sheath it's the one that produces the fat layer the Schwann cell produces the fat layer that we are calling the myelin sheath and it has the Schwann cell it has membrane called newly lemma new dilemma is a membrane of the Schwann cell so if you are to label it in the diagram here this membrane of the show and sell the Schwann cell is the entire cell but now its membrane is referred to as the new dilemma then we have said that the Schwann cell is the one that secrets or produces the myelin sheath that insulates the axon the other part that we need to mention are the dendrites the dendrites these words are extensions that receive and transmit now impulses to other nerve cells to the adjacent nerve cells so basically those are the main parts of a neuron that we've gone through and now we started by saying that the neuron is the basic unit of a nervous system it's the smallest unit of a nervous system a neuron is a cell modified for the transmission of electrical impulses and I say that nerve impulses are electrical in nature they flow like electric current the way the current flows through a wire is the same way the nerve impulses flow along the nerve cells now the general structure of an CEL shows a cell that is having a cell body with an extension and that extension is what we are calling the axon the axon is the main projection from the cell body we've also said that the cell body is done that contains the nucleus and that nucleus contains genetic material then also we mentioned that in the axon there is a fluid that is known as axial plasm which is the equivalent of the cytoplasm of a cell then we've seen the myelin sheath this is the sheet that insulates the odds-on and also helps in the propagation of the nerve impulses we have seen the show and sell that secrets or that produces the myelin chip and it has a membrane called the new dilemma and then finally we have seen the dendrites that are extensions that receive and also transmit impulses to the adjacent to the next and neuron now this something that also is good to mention here that if you look at the way the myelin sheath is deposited it's not continuous it leaves some gaps it leaves some gaps here and that gap is known as node of ranvier so it's also good to mention that that the gaps that are there they are called the nodes of ranvier and they help to speed up they help to speed up the transmission so they speed up the transmission of nerve impulses so basically that is the structure and function of the nerve cell so we are going to have the assignment on the same so there are three questions in the assignments the first question name the basic unit of a nervous system number to draw a world away labeled diagram showing a neuron or a nerve cell a well labeled diagram then number three what is the role of a the myelin sheath we have seen it in the diagram there and number two nodes of ranvier nodes of ranvier we have seen them there at intervals so we are going to stop there see you next time [Music]