0:00 You are about to start your second year of high school and you want to review all the acquired knowledge in science to start strongly in the school year I put in your hands the comprehensive video that will lead you, God willing, towards a successful start, so welcome to the Al- Khafa’a family In the name of God, the Most Gracious, the Most Merciful, and prayers and peace be upon our master and beloved, pray for the beloved Mustafa Welcome to the Al-Khafa’a army, second year high school students from all the states of Algeria In this video, God willing, we will conduct an intelligent review of the most important prior acquisitions in the science subject from the first year of high school, which will be a strong foundation for the second year of high school
0:45 Certainly, the journey of a thousand miles begins with a step Regarding the acquisitions in the science subject from the first year of high school, you have two units: nervous system control on the one hand, and hormonal control. We will need them, God willing, in the journey of the second year of high school. Certainly, there are new lessons. When we say prior acquisitions, we mean The basics from the first year of secondary school and these acquisitions in the science subject are for the experimental sciences branch because the mathematics branch there will definitely be new things. We are going to do, God willing, a smart review so that we see the most important
1:32 basics that we saw in nervous control previously as well as hormonal control because the second year of secondary school is a transitional stage between the first and third years. This means that you are preparing yourself for the baccalaureate certificate, so take it as a rule because the second year of secondary school is what? The transitional stage in which your studies must be good, especially in the science subject, because the science subject here definitely contains a lot of information that you must focus on from the second year of high school towards the baccalaureate, God willing. The first station we are going to see is what? Reminder of the gains about neural communication We are going to see all the basics of
2:19 neural communication We are going to go through the following points: The nervous system: What is a nerve cell and its types? The nerve fiber The spinal cord The nerve Walherian transformation experiments Also the reflex arc Resting potential Action potential We are going to see these basics in detail because we need them a lot in the second year of high school As for hormonal control, we are going to see what the concept of hormone and endocrine gland is The menstrual cycle in females Also the subclinical pituitary complex What do we mean by the pituitary gland Also the stages of the menstrual cycle in females Many details and we definitely need this unit in the second year of high school What I advise you to do is focus and
3:06 accurate observation because we are going to establish, God willing, a base from which we can launch strongly for the second year of high school and our goal is the baccalaureate certificate So with God’s blessing we begin a new happiness The first thing we begin with the gradual progression of the organism The gradual progression of the organism’s membership If An organism consisting of several systems. The system consists of several organs. The organ consists of several tissues. The tissue consists of a group of cells. The cell consists of a group of organelles. Organelles consist of a group of
3:53 molecules and finally, atoms. Atoms are the simplest thing. Now, an organism, for example, a human being. If the system has many systems, for example, the reproductive system, the circulatory system. For example, here is the nervous system. If we focus a lot on the nervous system, it consists of two parts: the central nervous system and the peripheral nervous system. This central nervous system contains the brain and the spinal cord. We know that the brain consists of the cerebrum, cerebellum, and spinal cord. We find this inside the
4:38 spinal column. As for the peripheral nervous system, it consists of cranial nerves, meaning that they come out of the brain, and spinal nerves that come out of the spinal cord. Notice with me this drawing. We also discussed it. So, this is the brain. It contains the cerebrum, cerebellum, and this is the spinal cord. So, this in blue is the central nervous system. This is also what comes out of The spinal cord and what comes out of the brain we call nerves. What comes out of the brain we call cranial nerves and they are 12 pairs, meaning spinal nerves, meaning they come out of the
5:24 spinal cord and they are estimated at 31 pairs on the right side and the left side. Don’t forget that the nervous system, God Almighty, what is the importance of this nervous system? It is voluntary movements, also sensation, conscious sensation, and so on. It has many, many roles. Also, the nervous system is connected to other organs, for example, the muscles are connected here in order to contribute to their movement and so on. So here, this nervous system is definitely made up of organs, for example, the brain. These are organs, and organs contain tissues inside, meaning they contain a group of cells. For example, here, the tissue
6:10 contains a cell. So, I wonder, isn’t it a single building block of the nervous system? We call the cell a nerve cell. Notice with me, if we say a nerve cell, you can call it a neuron, we can call it a nerve cell, if you wish, a nerve cell or a neuron. You notice what we are doing in Gradual system If we saw the components of the nervous system, we reached the cell. This nerve cell is drawn in the following form. Notice with me, the drawing is very important because it is the basis. We make the title. If we have a
6:58 cell body, notice with me. We also have here dendritic processes. Notice this drawing. You must know it. It is very important. If we have a nerve fiber, we will explain everything in detail. We have terminal branches. We will write the data. Notice with me, this is the entire neuron, which is the nerve cell. Where does the neuron form? This one in a star-shaped shape, we call it a cell body. If this one is in a star-shaped shape, we call it a
7:46 cell body. It consists of a nucleus. So, this is a nucleus, this is a substance, this is a membrane. Don’t forget it because it is a cell, and the cell has a nucleus, a membrane, a substance. We also have here these extra appendages. We call these appendages, dendritic processes, similar to trees. They are called dendritic processes. If the cell body has dendritic processes coming out of it, these dendritic processes are short. These are extensions that we call Cytoplasmic elongations, that is,
8:33 look at the elongation. Notice that from the cytoplasm, this membrane has elongated, short elongations. That is, the dendritic processes are what we write here. Dendritic processes are cytoplasmic elongations, or are they elongations of the cytoplasmic membrane short. What do you mean? So these dendritic processes, this is the second elongation. So, to come and explain more, the membrane elongates, elongates short extensions that form for us the dendritic processes. And this is the cell body, and this is the
9:19 entire cytoplasmic membrane. Notice with me this that I drew. This is the entire cytoplasmic membrane, right up to the end. And this is for the entire interior. So, now the cell body produces short extensions known as dendritic processes. You save them, and one long elongation is known as the cylindrical axis. That is, these long ones, we call them a cylindrical axis. So, this long one is a cylindrical axis. [Music] If the cell body has
10:06 short extensions, we call them dendritic processes, and this long one, we call it a cylindrical axis. Now, let’s elaborate more. This cylindrical axis wraps, that is, you find on it. Additions, notice with me what we find in it, the myelin sheath, this myelin sheath is a fatty insulating substance. This is what I drew in blue, this is the myelin sheath deposits. Notice with me, if this is what we call the myelin sheath, the
10:54 myelin substance, the myelin sheath, the myelin sheath covers the axis with interruptions, meaning you find it with interruptions every time it is cut, so this is the myelin sheath, what is above the myelin sheath, the Schwann sheath, if you find it like this, the Schwann sheath, here is the Schwann sheath, it is a cell with a nucleus, in this way, if you have the myelin sheath covering the axis, then the Schwann sheath, so this is the one in black, the
11:43 Schwann sheath, which contains a nucleus, Schwann is a cell, now you see interruptions, meaning the myelin sheath has interruptions, these interruptions are called Ranvier constriction, Ranvier constriction, in reference to the scientist who discovered if this is a axis It is covered by the myelin sheath, and there are spaces, there are gaps that we call Ramphian constrictions, Raphian constriction, which rises above the myelin sheath, Schwann's constriction, and the axon ends with terminal branches. If these are the ones at the end, we call them terminal
12:29 branches, this is the level from the one that came from the axon, the myelin sheath, Ranvier constrictions, Schwann's sheath, they end with terminal branches, we return and call it a nerve fiber. If here, it returns to us now, this is complete. Call it a nerve fiber. Did you notice? Look, if a cell body plus a nerve fiber plus a nerve fiber that ends with terminal branches, it gives us a nerve cell. If this is what we call a schematic drawing,
13:15 if an explanatory schematic drawing of a nerve cell or a neuron, it explains the structure of the nerve cell. What does it mean? What is a nerve cell? It is a cell body from which dendritic processes emerge, a nerve fiber that ends with terminal branches. What does it mean? If we were to do it like this, this is complete. A nerve fiber. Where is the nerve fiber formed? A cylindrical axon, which contains the monster. This is Topped by myelin sheathing deposits in it What are the interruptions? Interruptions we call it Rafie strangulation Topped by myelin sheathing If these are the components of the
14:02 nerve cell, it is preserved in the drawing and with its components because it can extend the data to other things. With Okasha’s books, the joy of the baccalaureate is complete. Good luck and success to all baccalaureate students, God willing. Okasha Library is more than just a publishing house. Now, we have types of this nerve cell. If the nerve cell, we go to its types. Notice with me if the types of the nerve cell in addition to these types of the nerve cell, the nerve, we will discuss it. If a
14:48 unipolar nerve cell, unipolar, we will explain it. A bipolar nerve cell, a multipolar nerve cell, what does that mean? See with me if we draw this star-shaped, the star-shaped one that I drew for you a little while ago. Notice with me this cell, this cell, why did they say it is multipolar because several extensions come out of it. Extension, extension, extension, extension Multipolar means how many from one pole 2 3 4 and so on if several poles come out of it then here it is multipolar there is the asterism in this
15:38 form you find this in the spinal cord and there is the pyramidal pyramid we find it in the brain these are just additions additional information in the form of a pyramid in the form of a star and this in the form of a pyramid it has several extensions meaning it is multipolar let's go to the bipolar bipolar this is how you find it this is the cell body the body the cell body two extensions come out of it the cell body two extensions come out of it notice with me the dipole a pair of poles a bipolar you find this here in the retina unipolar how is it notice with me this
16:26 is the cell body this is the cell body one extension only comes out of it a unique one here one extension comes out of the cell body we called it unipolar one unique pole so this is a unipolar nerve cell if you find this in the spinal ganglion these are the types of nerve cells now The cell that you are going to find a lot is the multipolar cell, this astrocyte that I drew for you, this is the one that we work with a lot, so you have seen this one and also the unipolar one, meaning these are the ones that we are going to study and you are going to meet with them a lot, this cell and this one, meaning we are going to see them a lot in the lessons now,
17:16 now if we go to the structure of the nerve fiber, if we do the nerve fiber only and its components, then this is its drawing, you have a cylindrical axis, the myelin sheath, that it is closed from the top and from the bottom like this, because the nerve fiber, if this is its cylindrical axis, if the first layer, the first layer is the myelin sheath, the second layer is the Schwann sheath, we call this a longitudinal section like this lengthwise, this is a longitudinal section, let us make the nerve fiber a cross section, meaning how is the cross section imagined with me, this is a nerve fiber, here it is with the components, we make a cross section for it, if in the
18:02 cross section like this we will see a circle Notice with me, if it is a cross section of a nerve fiber, you see a circle. If the first circle is a cylindrical axis, your job is to see it like this. When we cut it, we see if the first circle is a cylindrical axis above it. What is above it? What is this that I colored? The myelin sheath. If this is the second layer, the myelin sheath, it is an insulating material. Above it is also the Schwann sheath. If there is a
18:48 Schwann sheath, you will notice that this is a cross section. That is, when we come to see this crosswise, if here we see the first circle, a cylindrical axis. Like this, behind it we see the second circle, which is the myelin sheath. Behind it, the third circle is the Schwann sheath. So this is a cross section of a nerve fiber. Like this, the nerve fiber. Let us give you more information. There is a nerve fiber that is fused and there is a nerve fiber that is not fused. Notice with me, if you need additional information, you also have the nerve fiber. We
19:35 drew it this way: a cylindrical axis above it. Myelination Myelination is also between them Ranvier constrictions and then the Schwarz sheath which is in it is the nucleus of the sheath. So this we call a nerve fiber, a denervated nerve fiber, why did we call it denervated because it contains the myelin sheath. There is also a nerve fiber in this way, you will find it consists of a cylindrical axon only. We call this an
20:22 unmyelinated nerve fiber, meaning it does not contain the myelin sheath. If there are denervated nerve fibers and there are unmyelinated nerve fibers, this is due to the transmission of the nerve message, meaning the nerve message in this nerve fiber that does not have the myelin sheath is transmitted very slowly, but this nerve message here is transmitted quickly by jumping. So we will get to know this later in the nerve message. Now that we have learned about the nerve cell, the nerve fiber which is one of the components of the nerve cell, meaning the nerve cell consists of a
21:07 cell body, a cell body plus a nerve fiber that ends with terminal branches, the axon, we will get to know On what is the spinal cord that belongs to the central nervous system? The spinal cord, what are its components? If you must focus on it well, we will draw it with you so that you also get used to drawing it. Notice with me the spinal cord. If we draw it this way, it is very wonderful. This is the spinal cord and it is simple and it concerns you in
21:54 many details. If we also have here, we will explain all the details now. This is the spinal cord. Notice with me this is it. This is it. This is it. The spinal cord is composed of central gray matter, this is in the shape of the letter H. Central gray matter in the shape of the letter H. This is the reticular canal. This is gray matter. If central gray matter
22:39 in the shape of the letter H, you put white matter in it, peripheral white matter. This is the spinal cord. I mean, where does the spinal cord come from? It consists of central gray matter and peripheral white matter. Where do we find this spinal cord? Where can we find this? Here you find it inside the spinal column. Glory be to God. There is a cord called the spinal cord inside the spinal column because the spinal column is made up of vertebrae. Notice that inside these vertebrae, the spinal cord is inside them. This spinal cord, when they look at it, what they find is a
23:27 gray substance and a white substance. This is the spinal cord. You will tell me, teacher, and these that are coming out of it, what is this spinal cord? If this is the spinal cord, what comes out of it? So here are the spinal nerves. That is, here the spinal cord comes out. They are spinal nerves, a spinal nerve, and among them is the spinal nerve that I drew for you before. I told you spinal nerves, that is, they come out of the spinal cord from the right side and the left side. This is the spinal cord, and what comes out of it are spinal nerves, a nerve on the right and a nerve on the left in
24:15 each direction. That is, in each region, a spinal nerve comes out from the right and from the left. Now this is the nerve. This is a spinal nerve, and you cannot call it spinal, that is, it comes out of the spinal cord. This spinal nerve has two main parts in it. Anterior root and posterior root. So this is this piece like this. This is an anterior root and this is the Verrier root, a posterior root. The spinal cord forward, which comes here, is an anterior root and from it is a posterior root, this is forward. Notice
25:01 with me, if we go to a human, imagine yourself in the front. The spinal cord, the root in the front, we call it the ventral root. That is, from the ventral side, in the front is the abdomen and in the back is the back. If we start to say the dorsal posterior root, the anterior ventral root. Okay, how do you differentiate between the anterior root and the posterior root of the spinal nerve? There is a Dupartite spinal nerve. It has a posterior root and an anterior root. How do you differentiate them? There is what is known as the spinal ganglion. This spinal ganglion is what distinguishes the posterior root here. A spinal ganglion.
25:51 That is, differentiate between the anterior root and the posterior root with the ganglion. This is not what it was. If this cord and this nerve have two roots, anterior and posterior. Notice with me here this drawing. In the data, we also say this is in the gray matter. We call this one an anterior horn and this one a posterior horn because it is a Verrier anterior horn, horn. Notice with me this is a root, an anterior root, a posterior root, and this is the entire spinal nerve. This is a spinal ganglion. We call this a schematic drawing. This is an explanatory schematic drawing that shows a cross-section, not a longitudinal one. This is a cross-section of the spinal cord, if you pay attention to it. This is with regard to the spinal cord. In the
26:38 spinal cord, we found the following: in the gray matter, we found cell bodies, and in the white matter, we found myelinated nerve fibers, meaning they contain myelin sheaths. Notice with me how I represented it to you: a circle, a cylindrical axis, above which is myelin sheath. A circle, a cylindrical axis, above which is myelin sheath. If we found in the gray matter what, cell bodies, and we found
27:39 in the white matter, myelin sheaths. Did you see how I drew it for you? So this first circle is a cylindrical axis, above which is myelin sheaths, and we found myelin sheaths. So this is with regard to what we found in the gray matter and the white matter. I will explain more and come back to this information. Leave it. When we return to it now we will remind you of one experiment, an experiment, an experiment of impossibility, an experiment of impossibility, what does it mean, impossibility, impossibility means disappearance, it goes away, it is done, it has become transformed, it has disappeared, this experiment is the amoeba experiment, there is a scientist, the animal amoeba is gone, this is a living being, it is the
28:24 amoeba animal, it consists of a single cell, this cell contains the nucleus, what did the scientist do? He cut if he cut, he cut the animal into two parts, a part that contains the nucleus, the nucleus, and a part free of the nucleus, after a period of time, he noticed the following results, the part that was free of the nucleus disappeared, transformed, disappeared, but the part that contains the nucleus remained and was renewed if it was renewed, that is, it is not as it was, so what did we conclude from this experiment, he
29:13 concluded that the part that if he concluded that the part that contains the nucleus is renewed, it is renewed, focus on the word is renewed, that is, Julius Corto, we divided it, right, come back, or else it does not contain the nucleus, it is not renewed, they called it the experiments of impossibility, students Second secondary school, enjoy studying science with a strawberry flavor now. Get rid of all obstacles with confidence. The silver series. Everything you need in one book. Detailed lessons and
29:59 various exercises will give you the cornerstone for excellence in the baccalaureate, whatever your level. Your journey to excellence starts from here. Prepared by Professor Ben Kharif and Professor Katfi Sharif in cooperation with the Okasha team. Order it from the library near you in all states of Algeria. Okasha Library is more than just a publishing house. With Okasha books, the joy of the baccalaureate is complete. We also discussed this experiment. This experiment, if the transformation and renewal are at the level of the nerve fiber, if they go to the nerve fiber, they cut it. Look with me at the nerve fiber, which forms a
30:45 cylindrical axis. Myelination. If this is myelination, and the one above in the rose is Schwann’s myelination. If they cut the nerve fiber, then part of it is transformed and dies, and part is renewed. Yes, now as long as this part is renewed, this part, which is the nerve fiber, is connected to its nucleus. So here it has been proven that The cell body in the spinal cord, of course, is connected to the nerve fiber. That is, if we go here, we find a slope.
31:33 If this cell body is connected to the nerve fiber, it forms what is known as the nerve cell. Here, we have proven that the nerve cell is, in fact, a cell body plus a nerve fiber. That is, if they were to cut here, if they were to cut here, like this. If the cut were to be made here, where is the part that will become inextricable? What will die? Where is the part that is dependent on the nucleus? It will be renewed, and what you find free of the
32:20 nucleus will disappear. Here, this is it. This is the nerve cell. If the cell body, see where I drew it, and the nerve fiber extends, extends, extends. Here, if we were to draw this body again, this nerve cell, if this extension is a cylindrical axis, it is elongated. Then, if the myelin sheath is above it, notice with me. Then, of course, after that, myelin sheath. What did you notice? This is not This means that this is the cell, the nerve cell.
33:07 You notice that the cell body is here and the nerve fiber is an extension. Look where the nerve fiber is located. Guess with me a little bit. Where is it in the nerve? Yes, there, professor. The nerve is made up of a nerve fiber. What do you want this nerve cell to be? A cell body, a long nerve fiber. Where is the nerve fiber? Where did we find it? We also found it in the spinal nerve. So, the nerve is a nerve, from which the nerve is made up? There are cell bodies. No, professor, from which it is made up. The nerve is made up of nerve fibers. You see that this is a nerve fiber. If we cover the spinal cord, we should not forget it. And cover the streets. If the nerve is made up of nerve fibers,
33:55 is it made up of a single nerve fiber? So, let’s get to know that in the structure. If we go to the nerve structure section, what is the nerve made up of? Notice with me this drawing. You find it a lot, and we discussed it. It is an explanatory schematic drawing of a cross-section of the nerve. This is the drawing. Pay attention to it. If you notice with me, you will tell me, professor, this nerve. You made a cross section of it and look with me, this nerve that is in the spinal cord, make a cross section of it, we will see it as a circle, you see it like this, a circle if we see it as a circle, it consists of the nerve
34:43 sheath, the first layer is the nerve sheath, cover the nerve sheath, below the nerve sheath there are bundles of nerve fibers, notice with me, we will try to draw here in this way, so this first is the nerve sheath, this is the nerve sheath, inside inside there are bundles, bundle, bundle, bundle, bundle, this is similar to a cable, this one is for the triceps, the cable thread, this one is for the triceps, it looks a lot like it, so this is a bundle,
35:30 this is a bundle, this is the second bundle, bundle, bundle, what is this bundle made of? Inside there is work, bundles, bundles, what is it? Inside there are nerve fibers, fiber, fiber, fiber, nerve fiber, nerve fiber, nerve fiber, nerve fiber, each circle is a nerve fiber, each circle is a nerve fiber. So this circle is a nerve fiber, you will tell me, teacher, my brother We said that the nerve fiber consists of a cylindrical axon, a myelin sheath, and a Schwann sheath. Why are you drawing a circle in it? Because I see it in a cross section like this. In width, this means that we see it in the form of circles: a cylindrical axon, a myelin sheath, and a Schwann sheath. I didn’t explain to you if we
36:18 continue here. If we see it in a cross section, don’t forget that if each circle is a nerve fiber, then each bundle consists of a group of nerve fibers. This second bundle contains a group of nerve fibers. The important thing is that you draw circles and only the other details do not concern you. So here also is a group of nerve fibers. You noticed a group of nerve fibers and you continue. The nerve consists of the nerve sheath. Inside it are bundles of fibers. Each bundle contains nerve fibers. Here also, the interior gathers, gathers, gathers on those bundles, connective tissue. So this
37:04 tissue means a group of connective cells that hold them together. That is, those bundles are bound together by connective tissue. Each bundle with a bundle, connective tissue like this. There are also blood vessels. So here there are blood vessels, so this is a blood vessel because it is impossible that blood does not come to it so that it remains nourished, if this is not this, we call it a drawing, so the title is an explanatory diagram of the structure or a cross-section of the nerve, it is important and very important, so this nerve, okay, if you
37:51 commit, you will see how, if a hemogram or other, meaning this nerve, when we make a cross-section of it like this, this is the light, we saw in it the following: a group of fibers, you will tell me, teacher, but here you drew one fiber, here is one fiber, why is there only one nerve cell, there are many nerve cells, imagine this, another nerve cell, it also has a fiber, this is another nerve cell, another nerve cell, it has a fiber, these fibers, each group of fibers in a bundle and so on, meaning out of the billions of nerve cells, you do not have only one nerve cell, so to see the wisdom of God Almighty, notice with me this drawing, look here if
38:37 this nerve cell These dendritic processes, notice with me the cylindrical axon, this axon or this cylindrical axon is covered by the myelin sheath, then after the myelin sheath there is a sheath, what did you notice, and the Schwann sheath here, and this nerve fiber that extends from the cell body enters the nerve, it forms the nerve. So this is the nerve, did you notice this? So, see the components, how we made them, these components, how did it make them for you? So, the axon, the sheath, the myelin sheath, the constrictions, and the terminal branches, like this, so that the picture is clear. Now,
39:24 let us detail more. So, if this nerve cell extends to you in this way, look at the nerve cell, here it is. Let us divide it. Understand each part of it, where exactly it is located. Notice with me the cell body, where we found it. It is located in the gray matter. So, this cell body is located in the gray matter of the spinal cord. Okay, if it is the gray matter, let us go after the cell body, from which a nerve fiber emerges. The nerve fiber, this is its first part. This extends into the white matter of the spinal cord, did you notice?
40:11 Then, after that, a part of it It extends in what in the nerve, I mean like this, these are pools, and we are going to divide it, here is the gray matter, and after that the white matter, and after that the nerve and the final branches are found in the organ that it innervates. This is what it was, now this cell body, why is it originally, I mean, glory be to the greatness of the Creator, why is it the gray matter or the white matter, why is its color white? This white matter, why is it white in color?
40:58 Because here there is the myelin sheath, this myelin sheath gives it no color, the color of the myelin sheath. So here the myelin sheath is what gives it its white color, this is no color, the color of it. We call it white matter. Look, because here this part that contains the myelin sheath is in the white matter, and after that also in the nerve there is the myelin sheath and above it the myelin sheath, because here they definitely have different roles. So this cell is a multipolar cell, meaning several extensions emerge from it, which are these dendritic extensions, and this is the nerve fiber with books Akasha The joy is complete and the highest average comes and the ululations of the successful person come, God willing Akasha Library is more than just a publishing house
41:44 Let us now get to know what the reflex arc is, I mean the reflex arc you discussed in the fourth year of middle school, which is an involuntary action, an involuntary action, for example, when you touch something with a high temperature, if you immediately withdraw your hand, then in the reflex arc there is a sensory receptor, that sensory receptor, if the result of the stimulus is effective, as a result, for example, the temperature, then a nerve message will be generated, a sensory nerve message,
42:31 if a sensory nerve message, and we get to know the nerve message, who transmits it, a sensory nerve fiber transmits it, the sensory nerve fiber to the nerve center, which is the spinal cord, because we have things, we have the brain, the brain is the center of voluntary movements and conscious sensations, while the spinal cord enters into the brain, place in involuntary actions. We agree on this in voluntary movements, and this spinal cord is in the
43:18 involuntary, so the nerve center then converts if it reaches it A sensory message is transformed if it is transformed and processed it is transformed into a motor nerve message. If it is sensory, it becomes motor if the nervous center, the spinal cord, processes it. So here we call it a motor nerve fiber, a motor nerve fiber because it will transmit the motor message. Here, here is the sensory receptor, here is the executing organ, for example, withdrawing the hand. So these are the elements
44:05 that intervene in the reflex arc. Why did they call it a reflex arc? You have noticed that it comes in the form of an arc. You have noticed that it is a reflex arc, an involuntary action. If you have this, it receives a sensory receptor, for example, there are sensory receptors in the skin that receive this, for example, that stimulus, etc. Then a sensory nerve message is generated. Who transmits it? The sensory nerve fiber. Then after that, it goes to the nervous center. Then after that, the motor nerve fiber transmits it. Then the response here, for example, withdrawing the hand. So this reflex arc, if we go to this, what do we apply it to? On the spinal cord, we use this spinal cord and apply it. Look with me, we are trying to draw it
44:52 here. If you notice that here the message is transferred, for example, here the stimulus in the organ transfers the message in the posterior root. The posterior transmits the sensory message. This posterior transmits the sensory message because we learned about this in the experiments of the Omagenti. That is, the results of the piece that is this. Look with me with me here. They knew, that is, they knew where the cell bodies of the sensory and motor nerve message are located. These experiments are what proved to us this drawing that I am making. So here, this is a unipolar nerve. Yes, this is a
45:43 unipolar nerve that we studied previously. I told you that there are types of nerve cells. There are multipolar, there are unipolar. These are the ones that we will focus on. So, this nerve cell, this is a unipolar neuron, this transfers here in the nerve fiber. Look at the nerve fiber. This is a nerve fiber. Did you notice that it transfers the sensory nerve message in this direction? The afferent then passes it to the spinal cord. The spinal cord processes the message and then transmits it. It does not convert it into a motor message. If it is from us, it will become motor and from us, sensory. If the motor nerve message is transmitted via the motor fiber like this, and the
46:30 response occurs. This is the reflex arc that I drew here only. If you do not care much, then you will get into more details. Just care about this point, that there is a sensory nerve message in the afferent direction and a motor nerve message in the afferent direction. So, this is with regard to the transmission of the nerve message. Focus a lot on the nerve cells. Now, we said that there is transmission of the nerve message, transmission of the nerve message in the sensory fiber and transmission of the nerve message in the motor fiber. You see a motor fiber. I mean, this spinal nerve has sensory fibers and motor fibers. We called it a
47:15 mixed nerve. Now, what is the meaning of a nerve message? What is a nerve message anyway? So let's move to another element, which is the nerve message. What is the nerve message? You know what it is. You'll tell me, professor, what is it? There are those who tell me in this way, what is it? What is the nerve message? It tells you the work. But before we get into that, we must first go back to the nerve fiber. So this is the nerve fiber. It has a
48:02 cylindrical axon, above it is the myelin sheath. This is an electrical insulator. The myelin sheath has constrictions. Here, there is a Ravenous constriction, a Ravenous constriction, and after that, a sheath. What if it has a Schwann nucleus? This is the nerve fiber. Now, we will focus on the nerve fiber with its cylindrical axon only. Focus with me here. I mean, the experiments. We will focus a lot on this nerve fiber that has nothing but a cylindrical axon. This is a normal, unsheathed nerve fiber. I mean, there is no myelin sheath, it is just a normal constriction. Focus on what is
48:48 here. This has a cylindrical axon. Now, the scientists went to do something. They went to research the properties of the nerve fiber, properties. What are the properties of a nerve fiber if we find one that has a resting potential? If we are going to study now the resting potential, what is the resting potential? Scientists went to the nerve fiber and used a nerve fiber from a squid, a marine animal. They studied the properties of this nerve fiber and found the following. If they went and used an oscilloscope, if the
49:37 cathode oscilloscope, we call it an oscilloscope. If this is a cathode oscilloscope, notice with me, here it is. You also study it in physics. What does this cathode oscilloscope have? It has two electrodes, meaning this device will be connected to the computer so that the results will appear here and they will conduct experiments. If we draw this device in this way, we are only concerned with this circuit, which is what appears on the computer screen. Two electrodes come out of it. This is one electrode, for example, and this is two electrodes. Remember, “
50:28 Shh” means the word “head” but it means “pole, head, pole.” We do not call it “electrode.” Two electrodes, two electrodes, mean this device. What do you care about? It does not matter to you. This is a complete detail. You only care about this circuit. “Shh” we will record on it, which is the screen, and you care about what comes out of it. Two electrodes, a pair of threads. These electrodes, if the scientists did what they did, they connected this nerve fiber to the device, the oscilloscope device. This is an oscilloscope. So what did they notice? If they noticed with me that there was one electrode and
51:13 both electrodes were on the surface, they put them on the surface of the nerve fiber and recorded zero millivolts on the screen, meaning a line. They recorded a line at zero millivolts, “ Shh.” Its meaning is millivolts. Here they are going to measure the potential. We will explain later what it means. The potential. If we find zero millivolts, now they did the opposite. They put the two electrodes now, both of them inside, both of them inside. So they recorded the same thing, a line at zero millivolts. So here they knew that whether the surface or the
52:02 inside they had the same signal, meaning the surface and the inside, for example, if we were to measure on the surface, we would find one signal because there was no difference in the signal. But when we put them in a pair inside, we also found that there was no difference in the signal, meaning they had the same signal. Now they did the following experiment, which proved to them that there was potential. They put an electrode inside, meaning they put an electrode inside and planted it inside, and an electrode on the surface. They recorded one line, but at minus 70 millivolts, they found that what was there was minus 70 millivolts, meaning the line came at the bottom.
52:47 Here they discovered that the surface of the nerve fiber is positive, meaning that it is always positive on the surface, but on the inside it is negative. And here they said the fiber The membrane of the nerve fiber is polarized. Its meaning is polarized. It has two poles. It has a positive signal and a negative signal. It has two poles, a positive pole and a negative pole. The surface is positive and the inside is negative. This means that in the cell here the signal is negative, but on the surface the signal is positive.
53:33 And later, God willing, in the baccalaureate exam, you will learn that there are ions that are responsible for this signal. The important thing is that this is a resting potential. If we come from here and you find it like this at minus 70 millivolts, we call it a resting potential. So, when we tell you a resting potential, it means that the nerve fiber did not receive any stimulation. If in the absence of stimulation, the nerve fiber is at rest, it can go away. We decrease the potential. When we decrease its signal, the potential difference, meaning the voltage, we found it to be approximately minus 70 millivolts, minus
54:19 70 65. So, when we decrease it between the inside and the outside, we find a difference. For example, as we say between average 19 and average 10, there is a difference. There are nine like this. If they go to measure between the surface and the inside, they will measure and find the difference between them. That is, the difference in the signal between them is minus 70 millivolts. Now, this is rest at minus 70 millivolts because we put one on the surface and one on the inside. Now, teacher, this is what we call the one at zero millivolts. Zero. This is the second resting potential. That is, only here are the poles. Did we put them in pairs on the surface or did we put them in pairs on the inside? That is, the nerve fiber is resting, but you are concerned here with the fact that
55:06 this resting potential is estimated at minus 70 millivolts, and that the nerve fiber is polarized, its surface is positive and its inside is negative. Here, we discovered this with the cathode oscilloscope. We call it the potential difference, that is, a difference in the signal. There are more details, but you should pay attention to what follows. There is a difference in the signal. The surface is positive and the inside is negative. All the materials for all levels in the Akasha educational project. Notice with me here this drawing. So, this is his cathode oscilloscope. What is the path of the two poles, Mim and Aim, where is Q1 and Q2
55:52 here? This is the screen on which the graphics appear. If we put both poles on the same surface, this means that we record zero. This indicates that this one is positive and this one is positive. This means that it will remain at zero. Zero line. If we put them in a pair inside, we also record at zero. This means here because the inside is negative. But if we put Q on the surface and stop inside, then here we will record minus 70 millivolts. So there is a difference in potential between the surface and the inside. If we say that the nerve fiber is characterized by being polarized, its
56:42 surface is positive and its inside is negative. Now we move on to the action potential part. If this nerve fiber is in a state of rest and it is in a state of rest, its surface is positive and its inside is negative. Its surface is positive and its inside is negative. If it has a resting potential in the absence of stimulation, what do you think about stimulating it? If we go to the nerve fiber and give it a stimulation, what does this stimulation mean? We must give it an active stimulation, meaning we stimulate it, for example, by hitting it, for example, an electrical stimulation, etc. If this stimulation It will affect this nerve fiber. This nerve fiber was originally in a state of spiritual latency. Now, when the assignment and test come, you must serve. If the assignment and test are like an alert, if you start
57:28 studying, you start reading, you start memorizing. Yes, if the nerve fiber is in a state of resting potential and then returns to an action potential, this action potential is the result of effective alert. Everything you need in the methodology of natural and life sciences for all secondary school students. The silver series in the methodology from A to Z, prepared by Professor Katif Sharif Zeina in cooperation with the Okasha team. Order it now from the library near you. Okasha Library is more than just a publishing house. With Okasha books, the joy of the baccalaureate is complete. Now, the nerve fiber here, when we alert it
58:14 at first, is in a state of rest. If we make a recording here in the oscilloscope device, it is in a state of rest at minus 70 millivolts. This is a state of rest if one conductor is on the surface and the other is inside. And don’t forget that they are connected to the device. So this is connected to the device, if there is a resting potential, now we will make an alert to make an alert, the nerve fiber changes, as when you come to the assignment, it changes, the following will be recorded, suddenly we record a wave to make what for it, an active alert to make an active alert,
59:02 suddenly the wave is woven, did you see this wave, this is like this, call it a wave, a wave of depolarization, you know, we explain the wave of depolarization, a wave, what are the sea waves, a wave of depolarization, and what we call the action potential, clear your face from us when you find this wave, either call it a wave of depolarization, or call it the action potential, a positive action potential, this here, a positive action potential, so this is the action potential, how did it arise, what happened to the nerve fiber, teacher, brother, the surface was positive and the inside was negative, what happened to it, oh, its polarization changed, we changed its state, an
59:50 electrical state, see, it had an electrical state, what happened, it had an electrical state, it had a positive surface and the inside was negative, it had a positive electrical state, negative Suddenly, in order to make an active stimulus, the electrical state changes. To say it changes, its position changes. This means that after the active stimulus, the inside becomes positive and the surface becomes negative. This is what it means. The polarity changed. The surface was positive and the inside negative, but with the active stimulus, the opposite occurs. The surface becomes negative and the inside positive. If the polarity is reversed, if the disappearance is present, the disappearance of the polarization changes. This means the polarization changed, meaning that the surface is negative and
1:00:39 the inside positive. If it changes, what changes? In the electrical case, see how this was before the stimulus and this during the stimulus. Did you see the signal change? Did it change? The surface is negative and the inside is positive? So, did we notice this change? We noticed the change in the drawing. If it is a wave of depolarization, but this wave remains complete. It does not disappear. I mean, a wave comes and is held back. You do not review the assignment. And when you complete the assignment, it becomes a little troposphere. Like this, this means this change. After a while, the surface becomes positive again
1:01:26 and the inside becomes negative. Tell us what the action potential is. Let us know together what the action potential is. It is a sudden change in the electrical state of the nerve fiber membrane. A sudden change in the electrical state of the nerve fiber membrane. And soon the sudden change disappears. This change is temporary, meaning a little bit like this, and the nerve fiber returns. It did
1:02:12 not return to a state of rest before the stimulus. It was rest. During the stimulus, it was work. After the stimulus, it becomes rest. I mean, it returns to a state of rest. I do not have this drawing. Look at the beginning, the nerve fiber. The polarization of the surface is positive and the inside is negative. Suddenly, upon stimulation, the polarization reverses and the disappearance changes. The surface becomes negative and the inside becomes positive. Suddenly, it returns to being as it was. Then, the nerve message is spread and it is going. If the message is transmitted, what is the message originally? It changes in the signal. That is, when you see an action potential, this is an action potential. It has changed and returned to being as it was. It has
1:02:59 changed and returned to being as it was, so the nerve message is transmitted. Also, notice this drawing. If you see the nerve fiber in its normal state, its surface is positive and the inside is negative, you have a resting potential. That is, here, when you find at minus 70 millivolts, know that there is a current on the surface and a current on the inside, so that there will be a difference in the signal, because if there are two in the same place, there will be no difference, it will be zero. So here, and also after that, an action potential will be recorded. When, during active stimulation, notice with me. We will see the parts of the action potential. So, this is the stimulation signal. The alert signal
1:03:46 means that when we do the active alert, we record it in the membrane potential device. We measure the membrane potential in millivolts. If it is at minus 70 millivolts, then here you have a potential at the beginning. It was a potential, then after that the alert signal. Then there is a part. We call this depolarization. So the first part of the action potential from here, we call it depolarization. It reaches, you can say, about plus 30 millivolts, plus 30, 35, depending on what is important for
1:04:33 you to follow in the exercise. If it reaches about plus 30 millivolts, then after that, the repolarization. After that, we do this. We divide it again. See with me. We divide it. First, the repolarization, and after the part from here, we call it hyperpolarization. After that, the return to the resting state. We return to the parts of the action potential with you. First, the depolarization. This is the alert signal. Depolarization. Repolarization. Hyperpolarization. Return to the resting state. And in Baccalaureate, God
1:05:19 willing, you will learn more details about this. What is the action potential? It means the signal has changed. In this sense, see, the signal was the surface was positive and the inside was negative. When we applied the active stimulation, this part or the surface was negative and the inside was positive, meaning the polarization reversed and changed, but it quickly returned to what it was. It returned to the surface being positive and the inside being negative. It is normal for it to return to its resting potential state. The definition of resting potential is the electrical state of a membrane in the absence of any stimulation. That is, when you measure the membrane of a nerve fiber without any stimulation, you find between the surface and the inside its value is minus 70 millivolts. The
1:06:04 action potential is a sudden change. You see a signal that has changed, a sudden, temporary change. That is, it returns to being as it was temporarily for the electrical state. That is, the electrical state. If the resting potential is, we say the surface is positive and the inside is negative, this is an electrical state. When we measure between the surface and the inside, we find it estimated at minus 70 millivolts. That is, the difference between them is minus 70 millivolts between the surface and the inside. We make an effective warning so that the membrane does not change again and begins to memorize his lessons in order to follow the test and assignment. The one for memorizing his lessons means an action potential. You understand that. This is an action potential, which is a sudden change, meaning a little bit like this and it changes. A sudden change in the state of the electrical state. What it
1:06:55 means is the electrical state. What was positive becomes negative and what was negative becomes positive. A sudden change in the electrical state, meaning the signal, but the fiber quickly returns to its natural state, meaning that the surface becomes positive and the inside becomes negative. This means that here it is always a human being and it must return to what it was. We agreed now that we will move on to the law of all first thing for the nerve fiber and focus with me well on this because it is very important. This element is very important. For the first time in Algeria, the book that will make a difference in your study of mathematics in the second year of secondary school. A book explained in detail, page by page, in the
1:07:42 easiest ways, for free on the channel of Professor Nour El-Din. The second edition of the Silver Series book. Everything you need in one book. Study with complete comfort and confidence and be one of The outstanding students in all the states of Algeria, prepared by Professor Nour El Din in cooperation with the Okasha team. Order it from the library near you. Okasha Library is more than just a publishing house. With Okasha books, the joy of the baccalaureate is complete. The first thing we have is the nerve fiber. Here is the nerve fiber. Its surface is positive. Inside is negative. Positive. Positive. Negative. Positive. Negative. This is the second positive. From us, the surface of this nerve fiber. Suddenly, we stimulated it. We stimulated it with one
1:08:32 intensity. This means that here we stimulated it with one intensity, meaning with a value. So it remained in a state of rest, minus 70 millivolts. It did not change or remain in a state of rest. We increased it by giving it two stimulations with a greater intensity, meaning we increased the force. We increased the strength of the stimulation, so it also remained in a state of rest. But in stimulation three, we increased the intensity. We raised it a lot, so an action potential was recorded. In stimulation four, we increased the intensity, meaning we made it stronger. For example, if we stimulated it with five
1:09:20 here, we stimulated it with 10 here. We gave him a strong warning, for example, you review your lessons, review two lessons or five lessons, there is someone who reviews 10 lessons, there is someone who reviews 15 lessons, and here we made a warning of 20, meaning the intensity of the warning every time we increase the warning. When we made a warning of five, there was rest. When we made a warning of 10, there was rest. When we made a strong warning of 15, there was rest. When we made a strong warning of 20, we recorded two communiques. Oh, here, teacher, there is something new. Why did the nerve fiber not respond to warning one and
1:10:06 warning two? You will tell me because the warning, because the warning is ineffective. What does it mean? Ineffective, it does nothing. I review two lessons. I do not get 20. I do not do anything. I do not do anything in them. If the warning is ineffective, I do not do anything. It does not change the state of the nerve fiber. Leave it as it is, one communal rest, one communal rest. Remind yourself, but I do not respond to the mark. I do not give you 20. So this warning Ineffective now, see for me from us and go to alert three and alert four, the intensity of the alert has increased, the alert here is an effective alert if you know what it is, an effective
1:10:53 alert if the nerve fiber responds, then the effective alert if the nerve fiber responds, meaning if it changes, it is effective, if it does not change, it is not effective, if the alert intensity is alert 15 and alert intensity 20, these are effective alerts and these are ineffective alerts now we will ask you about the alert intensity, alert 15 and alert intensity 20, which is alert three and alert four, is it or why did the amplitude remain the same, meaning the working potential reached 30 and dropped again? Here it reached 30 and dropped again, meaning the amplitude is Shh, meaning the amplitude is this rise, we
1:11:40 call it the amplitude, the amplitude of the working potential, the amplitude here means it is estimated at about 100 millivolts, the amplitude means the rise here we recorded up to 30 and here the amplitude itself did not change, meaning you never find the working potential very large, meaning you never find, for example, a potential For example, if you work in this way, you will find that the working potential reaches up to plus 30 millivolts, and you will find another working potential in this way that reaches up to, for example, plus 60 millivolts. It is impossible, impossible, to find a fixed working potential,
1:12:28 its amplitude does not change, meaning it reaches 30 and then stops. As you know, there is a mark of 20 over 20. Did you not find someone who exceeded 20 over 20? This means that the amplitude is fixed, meaning it reaches plus 30 and stops. It was not above it, and the one who works harder will get 20 over 20, and the one who works harder will get 20 over 20. So, the all-or-nothing law, what does it mean? The ineffective stimulation does not serve the nerve fiber, it does not respond. Also, the amplitude of the working potential is fixed, no matter how much the intensity of the stimulation increases. So, no matter how much we see it, note that no matter how much the intensity of the stimulation increases, the amplitude of the
1:13:15 working potential is fixed, no matter how much the amplitude increases, it is fixed. Do you understand? Like the mark of 20, it was not above the 20 Law of all first, something responds or does not respond, so it will be an effective stimulus that responds, ineffective, or unresponsive, and the amplitude of the action potential is constant, no matter how much the intensity of the stimulus increases. We focus a lot on the increase of this number. See, if it increases, it was one unique potential or two communal pairs, and if we increase the intensity of another one, they increase again, we have three communal pairs, and it is going, meaning that the more we increase the intensity of the stimulus, the one that increases increases, the number of action communal pairs increases. For example, here, the
1:14:03 intensity of this intensity, we record one more intensity potential, we record two communal pairs, the largest intensity, we record three communal pairs. If the one that increases increases, the number of potentials increases, the action potentials, and the amplitude is constant. You see in the amplitude that it is constant and does not change, but the number of action communal pairs increases with the increase in the intensity of the stimulus. When you increase the intensity of the stimulus, the amplitude remains constant and the number of action potentials increases. This is so that you know the difference, meaning that whenever one says the stimulus, the frequency will increase. So, we call it the frequency of action potentials. Did you hear me?
1:14:53 This is one, two, or two potentials, they are called Frequency of two frequencies, a pair, this is one, two, three, three frequencies, if three, what are the repetitions, repetition, how many times was the action potential repeated? It was repeated a pair of times because the intensity of the stimulus is very strong. It was repeated three times because it is very strong. So this is what we call frequencies. So when we come to draw for you like this, we say frequencies [music] action potentials. What do we mean by frequency? We mean by it frequency repetitions, three, four. We say four frequencies,
1:15:39 meaning four, four repetitions, four frequencies. For you, this is the work. This was not so that we can increase it for you like this. Two frequencies for you, the work. This is the nerve message. This was not what it meant. The nerve message, how do you read it? When we give the stimulus to the nerve fiber, you read it by frequencies. So when we come to give a stimulus here, an active stimulus. So here, what are we going to record in the device? We are going to record, for example, two frequencies. Action decompositions mean that here the nerve message was positive, negative, becomes negative, positive, and it continues to be transmitted along the nerve fiber. How do we read it? How do you see the
1:16:25 nerve message? See it, the message. Nerve encoding, you read what it means, it encodes, so we read it, how do we see it encoded by the frequency of action potentials, so we read it, we see it by the frequency of the action potential, so how do you know that there is a transmission of the message, how do you know it by this potential? If you find a potential, say there is action. If you do not find one, tell me it is rest. So this is the nerve message, this nerve message is encoded by the frequencies of the action potentials. The more the intensity of the stimulus increases, you will find an increase. This is the transmission of the nerve message.
1:17:11 All materials for all levels in the Akasha educational project. Notice with me here in this drawing, it does this for you. Its meaning is intensity. See, if the intensity was very small, the nerve fiber did not respond. A larger intensity did not respond. A larger intensity did not respond. A larger intensity responded. A larger intensity responded. A larger intensity responded. A larger intensity responded. But here you find two frequencies. Here, for example, you find three frequencies, meaning that the more the intensity of the stimulus increases, the number of action potentials increases, but the amplitude is constant. The amplitude always remains constant here. This is Amount What is the amount of stimulation We will ask you,
1:18:00 notice with me, look here if this intensity is five, the fiber did not respond, it remained at rest, intensity 10, the fiber did not respond, go to intensity three, when we did 15, it responded, when we did 20, it responded, with what capacity, with two frequencies, does it mean the frequencies increased, where is the stimulation threshold, look at the threshold, the stimulation threshold is the lowest value at which the nerve fiber responds, go here and where it is, the lowest intensity at which the nerve fiber responded, this is intensity
1:18:47 15, here it did not respond, here it responded, the lowest value is the stimulation three out of three, and the lion goes and responds, the smallest thing is the stimulation threshold of 15, and the one in the nerve goes and responds normally, here we call it the stimulation threshold, second secondary students, enjoy now studying the science subject with a strawberry flavor, get rid of all obstacles with confidence, the silver series, everything you need in one book, detailed lessons and varied exercises that will give you the cornerstone for excellence in the baccalaureate Whatever your level is, your journey to excellence starts here. Prepared by Professor Ben
1:19:35 Khrif and Professor Katfi Sharif in cooperation with the Okasha team. Order it from the library near you in all the states of Algeria. Okasha Library is more
…
