 Welcome back to the lecture series in NPTEL on Bioelectricity. So, we have introduced the course in the first lecture and in the second lecture we went ahead and started with a graphical representation of the course, the way it will progress. So, in that process we started with the inanimate object or inanimate object from biological origin. We talked about how the thermal regulation is being done, we will be discussing it under the following heads like you know the system identification, the biological or bioelectrical phenomena and then we will be talking about the instrumentation needed and the advanced applications. So, in that process we have finished with the inanimate world what we will be dealing in the course, we talked about the insect world, we talked about the plant world. What we have not talked yet is about the animal bioelectricity, the world which is most explored among all these where there are lot of applications for biomedical perspective as well as for different form of prosthesis and everything. So, today we will start with the graphical representation of the animal electricity or animal bioelectricity what we will be dealing. So, once again let us coming back the way we started with the other ones. So, we will make four columns system identification. So, system identification will be our first column identification, bioelectrical phenomena, instrumentation, the advanced application. This we are all doing under the title of electrical. So, again following the same scheme of things. So, we will identify the system, we will talk about the phenomena, we talk about the instrumentation and then we will talk about the advance application. So, the first question which we will attempt to answer here is the origin of the bioelectrical phenomena. In other words the cellular electricity at the cellular level how electricity is being generated. So, that needs us to go in depth with the membrane structure of the membrane membrane potential and the flow of charges across the membrane which leads to the generation of electricity. So, start off with we will study about the membrane and please ensure to keep this chart in mind all the time membrane structure which leading to potential difference delta v charge transfer or charge transport across the membrane across the membrane and the kind of instrumentation. So, here there are few more things. So, whenever we talk about the membrane structure and the charge transport across the membrane but to realize that these are semi permeable membranes we are talking about and they regulate the flow of charges especially or exclusively these are ionic charges which are flowing and they are gated through the membranes using the smallest unit which helps in the gating that is the ion channels. So, we will be studying about the ion channels which is the smallest known entity which helps in or which regulates the flow of ion across a membrane. So, we will be talking about the membrane structure we will talk about the structure of the ion channels and within the ion channels we will talk about voltage gated ion channels I am just putting ion channels as I see and ligand gated ion channels I just got into the other columns do not worry. So, membrane is the most I should say the most primary level where the electrical impulses gets generated and from there it keeps on travelling through from one membrane to another to the third to the fourth likewise and the major techniques which have evolved in the study of membranes includes voltage clamp studies, current clamp studies, patch clamp studies, single channel current measurements. So, talking about the instrumentation out here we will talk about voltage clamp and I will come to the exact meaning of all those things voltage clamp, current clamp, patch clamp within the patch clamp we have whole cell recording we will talking about. So, that there is a whole classification which I will be coming to this whole electrochemical or electro physiological measurements extra cellular, intra cellular within intra cellular you have the whole series of patch clamp voltage clamp, current clamp whereas, in the extra cellular also you could have those thing, but using extra cellular electrodes. So, then we will be talking about extra cellular recordings which will include your micro this is just the sign of micro micro electrode array or field effect transistors FET ok. So, there is a. So, this section what you see the voltage clamp, current clamp, patch clamp, whole cell recording, extra cellular recording and by the way all these others fall under the most of them falls under the intra cellular recording. So, within the membrane structure we talk about the we will talk about the potential difference and most importantly we will have to talk about to start off with actually we will have to talk about the out here how membrane potential is actually generated this is the first and foremost question which we needed to answer and from there. So, now we have a potential difference this potential difference leads to a charge transport across the membrane and in this whole game of understanding the membrane structure and I should put it more correctly membrane structure and dynamics because there are other events which are taking place let me move on to the next slide where we will be talking about what are the other events which are involved in this process. So, we will be talking about the membrane. So, where we are with the membrane structure membrane dynamics we will be talking about Nernst equation and we will be talking about Goldman Hodgkin and Kurtz which is also called GHK equation which is nothing but extension of the Nernst equation. So, here we will be talking about the counter forces of diffusion and delta V the potential difference and the diffusion how that you know how these forces are regulating the or other we can say the charge mobilization. In other words what we want what we wanted to say or what I wanted to highlight here is that say for example, you have across the membrane something like this a positive charges negative charges. So, and this is the membrane essentially what we are trying to highlight will be trying to highlight here is that under the normal diffusion say for example, you have 100 molecules of NaCl sodium chloride on one side you have 10 molecules of sodium chloride of one another side and if you allow the free diffusion eventually what will happen 100 on this side 10 on this side 100 plus 10 makes it 110 110 divided by 2 which makes it 55 55 on both side there will be 55 5 molecules. But think of a situation where you have 100 12 molecules of NaCl. So, which dissociates into Na plus Cl minus charges on the other side also Na plus Cl minus charges and apart from it there are few other charge molecules and the membrane which is there is semi permeable it will not allow everything to pass through and how the membrane will balance itself across across it two sides that is what we will be talking about the dynamics part of the membrane and because that is those are the governing processes which regulates the flow of ions across a semi permeable membrane and here I can go back to the previous slide. So, whenever we talk about these kind of biological membrane essentially we are talking about semi permeable membrane. So, we will talk about the membrane dynamics and then we will talk about the once again with respect to individual cells will have to come and there will be talking about we will talk about the nerve cells which are excitable cells. So, in the body there are three kind of excitable cells nerve cells cardiac cells and few other cells on of course, the let us just see the excitable cells or electrically excitable cells of the body electrically excitable membranes or call it cells. So, membrane is covering the cells cells of the body. So, there are you have the nerve cell you have muscle mostly skeletal which is more pronounced you have other muscle which is within the muscle that we do like this. Now, I am doing it right cardiac and skeletal essentially we will be talking about nerve bioelectricity skeletal bioelectricity and cardiac bioelectricity. So, these are on the left most column if I had to talk about the identification of system. So, this is the broad identification of the system and mind it these system are all interlinked. So, for example, this nerve is regulating. So, there is an interaction that falls under the interface zone of this where we will be talking about nerve muscle junction and how to study that or say for example, if you pick this up the way nerve regulating cardiac muscle and in this situation we are talking about the skeletal muscle of course, cardiac muscle regulation. So, while we will start with the structure of the membrane that will be your generic structure where we will talk about this is how the membrane looks this is how the potential difference across has been maintained and these are the different smallest unit ion channels which are regulating and from that generic introduction we will move on to the specialized cell types which is nerve cells like all the three excitable cells muscle is called muscle the cardiac muscle. So, coming back to the previous slide where we were so where we actually started. So, within so second let me so this is this is the overall outline to start of it this thing and then we talk about the membrane dynamics what will be studying in the dynamics part and then we talk about the. So, in this classification what we are going to study in the nerve cells. So, within the nerve cells we will talk about the impulse propagation this is exceptional important then we will talk about the once again we will talk about the synaptic connections and in that whole process with the nerve system we will talk about memory and learning because these are some of the most important bioelectrical phenomena here we will talk about the spinal cord computation and injury then we will among these nerve cells we will talk about some of the special senses comes a special senses we will talk about the eyes the ears then nose and these have very straight for output whenever we talk about the eyes ears and nose because these are the organs which has opened up the say open up the scope for prosthesis because the first prosthesis which was done was the cochlear implant. So, from here we will move on to essentially to from here we will talk about that among the advanced application about cochlear implant which is an 8 electrode system then the eyes will talk about retinal prosthesis this is in the case of nose in human being that is not as a strong as the rodents it is more of a research interest of understanding what are the different orders and they have of course profound implication in perfume industry and all other places. So, they are more like a inspiration for odorant sensors. So, for the sensor devices and within this part spinal cord injury we will talk about among that advanced application we will talk about different electrode stimulation or and sorry spinal cord chip likewise then in the case of memory and learning this is one of the most challenging frontier where we will be talking about different B brain stimulation techniques different research which is currently going on to replace a part of the brain with a chip to you know handle situations of like Alzheimer's or some other neurodegenerative diseases or we will talk about how a brain can cross talk with a robot and all those kind of things. So, it will start with the stimulation it is one of the areas then implanting electrodes then this implanting brain chips these are the futuristic dream of mankind. So, what essentially transpire out of all these things is this that we have to understand the very basic fundamental ideas first specially in terms of if you go back to the previous slide you have to understand the membrane potential you have to understand the charge transport across the membrane we have to understand the dynamics of the ion channels and we have to understand the how the nurse equation Goldman Hodgkin cuts equation and other all other things are regulating the whole process, but then the next phase which is the most challenging phase of all this game is something if you look here. So, if you look very concentrated on this site like if you really look very carefully to this side this whole part is taking us to a different zone that is basically what we are talking about is you are implanting or you are introducing something inside your body in the form of electrode or in the form of a chip, but mostly at the form of electrode form of an electrode. So, that requires a different kind of expertise. So, we will just enumerate bit of it. So, that you appreciate that why these areas are so very challenging. So, what I will do I will try to do it more on a diagrammatic reaction. So, say for example, just think of it if this is your brain and this is the spinal cord moving now we are introducing an electrode into the system like this or say for example, or maybe a surface electrode like this. So, the very moments and these are I am just putting the sign as E minus as the electrode and this is of course, brain and the spinal cord. So, the very moment you are introducing something into the brain or into spinal cord you are introducing a foreign object into the system. And essentially how these individual cells are going to interact with that foreign object is the most fundamental challenging problem that falls under the field of cell electrode interface. This interface is extremely important because electrode this is the zone where look how diverse the field becomes this is the zone which needs your understanding of materials chemistry of the material. Then you have to understand the electro chemistry then you have to understand the which is the interface area out here that interaction which is the biocompatibility and then long term impact. So, this whole field of cell electrode interface is exceptionally challenging and that is where lies the catch what are the newer and newer electrode materials which mankind could develop which could help us in progressing into the field of man machine interface or neuro prosthesis and neuroelectric interface much more easily it should seem in very easily without any problem. So, that is the whole field in its own merit and that needs different kind of training to understand. So, this is one thing which will be highlighting as we will be talking about micro electrode areas will be talking about different electrode materials which are being used. So, that is the part where we will be talking about the whole instrumentation and everything. And talking about its implication if you look at it we have already talked about if you go back or out here once again so the brain stimulation implanting. So, these are all material things electrode stimulation spinal cord retinal prosthesis cochlear implant sensor devices. So, if you look at all of them they all need electrode materials. So, on one hand we are dealing with the biological system, but one other hand you need a deep in depth understanding of material science otherwise it is exceptionally challenging even to handle a single problem in this field. So, now what we will do we will talk about few more other areas. So, this zone talking about nerve muscle junction understanding nerve personal junction. So, this could have profound impact in understanding the field of robotics could we have a robot which make the moment of the arms. So, gently it could do like this it could walls through it could move through it could do like this all these different degree of freedom. This privilege we have because we are under the continuous control of the nervous system which helps us. So, this is the area the nerve muscle junction what I try to highlight out here has profound impact in future robotics future robots may use some of the algorithms what are being. So, basically first of all you have to understand we have to understand translate this algorithms of body. Body algorithms have to translated into for a machine algorithm to execute the job. So, this is how the understanding of nerve muscle junction could be of big help other than that there is another side of this whole field that is the case of patient with amputation. So, for example, a person has say amputated hand or amputated legs could we. So, say for example, here is a situation say for example, here is a human being this is an intact human being. Now, there is an amputation is gone now we can put an artificial artificial limb out here, but how this limb will cross talk with the brain what will be the signals which will be put here that all falls under understanding these algorithms how nerves are controlling the muscle could we have could we translate this in terms of some kind of electrical gadget here after understanding the algorithm or electrical interfacing could we do that for an amputation. So, these are some of the fundamental things which we needed to understand while we will be talking about the nerve muscle interaction from a very application oriented point of view. We will do the very little bit biology, but will be more concerned about how those signals could be translated in terms of a computer algorithm that we could design something which could execute if not to the level of efficiency of a normal human being, but you know to some degree. So, that the life of this individual becomes much more easier. So, that is one area we will be kind of highlighting here as an advance application while talking about this part the story nerve and cardiac muscle. So, these are some of the understanding which has profound impact in extra corporal devices for those of you who are not aware of extra corporal devices these are devices you have to check the spelling problem my spelling is wrong here these are the devices which are used outside the body. So, for example, somebody the best example is this somebody is having a kidney problem fine the kidney is unable to purify the blood. So, what they do they put an artificial kidney outside the body and they bypass the fluid which moves through that device and purifies the blood and put it back in your body. So, you pretty much carry the device with you or when you are lying down so it depending on how fast it has to be taken care. So, this extra corporal device devices are fairly prominent in before even we have a very ready prosthesis out there. So, this is one of the root. So, these nerve cardiac interaction could have such a scope apart from it understanding is could help us to develop the artificial heart which currently only of course only one company in the world which is doing. So, but there is lot of room lot of understanding apart from it is another area which is the most prominent area currently is the area of pacemakers once again where basically. So, the pacemaker pacemaker is nothing but the heart has a rhythm by which the electrical impulses are being transmitted from one part like from one side of the heart to the other end from one I should say from one corner to the other corner. So, that piece is set by the specific cells of the specific circuit within the heart and those are called pacemaker cells. So, say for example, for some reason another these pacemaker cells goes where they were bad they were not functioning. So, what to do how to bypass the problem the only way to bypass the problem is that you put a synthetic pacemaker on the surface of the skin out here which set the tone for the conduction to take place and there is a technical term though for it. So, basically heart is divided into two my two system which functions in complimenting each other one is called the conduction system which is basically the pacemaker system and other one is called the contraction system which actually executes all this you know the heartbeat and all those kind of things. So, if the conduction system goes bad how to you know ensure that we are doing fine. So, that is where comes the whole field of pacemaker and pacemaker implantation is a very common process currently, but there is lot of room for improvement of pacemaker because this is another thing which is very similar to what I drew for you is something like this. So, where you are putting electrode like this. So, here essentially what you are doing if this is your this is the heart with the four chambers. So, essentially what you are doing at the surface of the of the skin you are putting and stim something like this. So, this is essentially is the story of pacemakers which is nothing but signal generator. So, here the electrode is not really picking up signal it is generating signal at a certain frequency and a certain wavelength. So, that is the other area where there is enormous scope of understanding and apart from it the way these rhythms are moving across the heart the way these waves are moving out here the propagation of the wave. So, this propagation could be dealt in the field of e c g or e k g. So, we will talk more on this on c stand for cardio electrocardiogram electrocardiogram or k is for the German cardio. So, this is something which all of you must have seen that there is a kind of traces whenever you see a screen and that the based on that there are intervals like you know p e q r s t likewise you know. So, we will be talking about those electrocardiograms and all those electrocardiograms are being interpreted and what are their significance and how that helps the doctor to decide whether this individual needs a pacemaker or not. So, these are the things which we will be studying in the cardiac system. So, we have talked about so the way we started is go back. So, we talked about the we will be talking about the membrane structure and dynamics and how the potential is generated the potential difference leading to the charge transport across the membrane. We talked about the voltage gated ion channels we will talk about the ligand gated ion channels and in this whole section of techniques we will talk about all the major techniques will be dealing out here. As I told you that we have a section on the techniques yeah then we will be talking about the dynamics part where I highlighted that we will be talking mostly about nurse equation and how this is being govern the governing dynamics for this whole process. Then we will be talking about the nerve within the nerve cells we will talk about the nerve propagation synaptic connection learning and memory spinal cord computation and injury and the special senses which are exceptionally important for our survival the eyes ears and nose and simultaneous retinal processes cochlear implant and sensory devices respectively. From here we will talk about the electrically within this classification we have this nerve cells out here the skeletal muscle you have the cardiac and we will talk about individually and how those could be used for amputation patient amputi patients or in robotics and then we will talk about the electrode implant and specially within the cardiac and how the EKG traces could be used to understand the pacemaker whether the person needs a pacemaker or not. And here I highlighted that how this cell electrode interface demands your understanding of material its bio compatibility its long term impact and the electro chemistry of the material and in that same line there is something called corrosion there the fidelity of signal how long the signal there because the thing is that whenever the so to realize here in this diagram whenever this electrode is in sight. So, essentially what is happening if I redraw this situation it is like this. So, if I represent the cell by a green color like this you have the electrode as red color like this. So, this is your electrode and this is your cell. So, at this interface zone at this interface zone it is a very dynamic zone this is the zone where this cell what you see out here is secreting a lot of things and the surrounding fluid is acting with this electrode. And because of this gap first of all there is a gap you could see that there is a gap this gap influences the signal the fidelity of signal is one thing this gap is very good at doing part from it what happens over a period of time this cell is secreting as these arrows are showing the secretion these secretion could if you kind of make up slightly more bigger image of this will be like this that if this is the electrode over a period of time what you will see is out here will essentially see that there will be coating of something like this. And still the cell is out here and this gap may keep on increasing and that definitely reduce the fidelity of the signal what is reaching to the electrode. So, these are the some of the stuff what we are going to deal with in the cell electrode interface which is exclusively it is a very challenging area. And continuously there is research going on I will try to give you the feed of the different research which has been done apart from it we will talk about some of the. So, I told you that we will be talking about lot about the bio energy. So, what we will do this is one area which I have not really highlighted while showing the scheme of things. So, in the scheme of things I told you that you know you have these under the four columns in the graphical representation. So, we will talk about in that among the system of some of the ancient molecules some of the very ancient molecules profound biological and electrical potential. So, some of the molecules will be dealing here will be some of the semiconductor molecules like sulphides. So, we will talk about them we will pick up one different section something like we will talk about f e s 2 one of the major one will be talking about f e s 2 and we will talk about it is a solar cell potential. And the reason why I pick up f e s 2 because these are iron sulphur clusters are common in the membrane. They are pretty much integral part of the membrane and we will talk in depth about water the advancement which has been made because mind it among the first semiconductor material which were developed which was kind of discovered was galena which was nothing but lead sulphide. So, sulphide has remain very much integral part of our development. So, this is one section which will be separate out. So, here of course again under the same classification we will talk about system identification the phenomenon instrumentation what will be needing. So, that will remain pretty much the same instrumentation and advance application within the advance application is our this section which I actually did not this is the past part which will be the advance application. And phenomena is of course the light sensitive molecule and as we will move through this you will realize that why I picked up this particular molecule it has some very unique unique properties which is far better than the silicon based electronics what we are currently. So, much involved in it. So, this is the overall layout the first three classes what I told you that I will be introducing you to the into the course. So, these are the first one let me do let me just let me do your favor let me open up my first lecture. So, this is what I wanted to show you guys here. So, this is the introductory part of the module which I just now I finished the first three class two to three class what I devoted on introducing you to the whole subject. So, this is where all those three graphical representation and everything comes introduction graphical representation of the subject. Now we will move on to. So, this part is all taken care now now we will pick up one by one all this what you are seeing in section two section and every time I will come back I will just see how far I have reached in this whole scheme of things what you see in front view now the first three lectures are gone. So, now we move on to so we will make a call whether we are moving to section because as I have told you we can pick up this this this this anything at any point we can again come back. So, we will keep it very lucid very simple and my expectation is very clear here just your basic high school or whatsoever and we will stick there we will not go anywhere beyond it because the whole idea is to appreciate electricity across nature it is not about you know knowing high end equations out here or you know very intricate phenomena it is about first of all what it needed is that you have to love the subject you have to appreciate it and once you start loving the subject then you get in depth into it you like this part you will get into it. So, the whole philosophy of this course is appreciate it appreciate all over nature there are so many beautiful things which are happening is just you have to try to look at it. So, now I will end my module one where I basically introduce you to wide range of bioelectrical phenomena and now I will pick up one by one and I will expose you to the different events thanks a lot.