[Music] let us just start by looking at our our lesson plan now on our lesson plan today we have what is the nervous system which is what we are supposed to discuss today we are going to discuss what is the nervous system what is the nervous system made up of and then we're gonna discuss the central nervous system or the cns in abbreviation and then we're gonna discuss the brain and the structures of the brain and the functions of the structures of the brain and then we're going to look at the nervous tissue which is the three types of neurons and then we're going to look at the reflex arc and then we're going to look at the reflex action most people confuse the truth but i will just differentiate them because they're not the same and then we're going to look at the peripheral nervous system which is abbreviated as the pns and then we're going to look at the types of the receptors and last but not least we're going to look at a brief summary of the entire topic that we are going to discuss today now moving to our next slide as i told you guys we need to know what is the nervous system now the nervous system is a system that is responsible for processing and transmitting information throughout the body and it tells the body how to react to stimuli similarly which is the changes in the environment and then it coordinates the various or the different activities of the body for example working hearing and seeing and the human nervous system is actually divided into two sections or two parts we have the central nervous system the cns and we have the peripheral nervous system now we are going to start by looking at the central nervous system now the central nervous system is made up of the brain and the spinal cord only remember the central nervous system is made up of the the brain and the spinal cord now the brain is a particular structure which is protected by the bones of the cranium the cranium is the part of the skull and is surrounded by the three layers of the membrane three layers of membranes are what we call the meninges which therefore protection the brain is what is protected by the cranium and also by the three layers which we call the meninges and the brain consists of what we call the cortex which is the gray meta and then this chord text it consists of what we call the cell bodies and then we're gonna look at the medulla oblongata of the brain as well which consists of the nerve fibers or the exons and is called the white matter the brain is made up of two different components is made up of what we call the gray and the white metal now the spinal cord the spinal cord is protected by what we call the vertebral column on the vertebrae and is also protected by what we call the cerebrospinal fluid is which is a very important and a very special fluid it plays a very important rule and the nerves from the body parts enter the spinal cord as they do one pair of spinal nerves and the spinal cord is the pathway for all the impulses that are conducted or transmitted to and from the brain and also processes what the reflex actions and we have got what we call the sympathetic and the parasympathetic nerve impulses which are conducted which are conducted along the spinal cord to all organs you're gonna understand what i'm trying to explain here when you're looking at the diagram now let's just look at the brain remember our brain unfortunately i don't have that structure at this moment but i'm gonna describe the structure of the brain now the brain is made up of two hemispheres and these hemispheres they are separated by a particular structure which is what i'm going to actually discuss with you it's one of the parts of the brain now these hemispheres we have the right one and the left one now the right hemisphere controls the left part of the body and then the left hemisphere controls the right part of the body now before we move forward i want us to look at the click the three layers that surrounds the brain which we call the meninges we have the dura mater the arachnoid and the pair the pr matter what i call them the dab dap in order for me to remember them now these layers there as i'm labeling them here as i labeled sorry them here they followed like each other as they are here this is the outermost the outermost layer and then this one arachnoid is the in the middle layer and then this one is the innermost layer and then between the middle layer and the innermost layer which is the arachnoid and the pier mater we have got a very special fluid which plays a pivotal role which is called the cerebrospinal fluid now let us just look at this and the parts of the brain now the brain has a cerebrum which is this part here the biggest portion of the brain and then it has the corpus callosum the structure here and then it has the medulla oblongata which is this part here and then it has the hypothalamus which is the part here above the medulla but below the copper scalosa and then it has the patch here which is this part which is called the cerebellum now people confuse these two structures the cerebrum and the cerebellum there are two different structures guys they are not the same the cerebrum is the biggest portion of the brain but the cerebellum is smaller than the cerebrum and they have different functions as well now the cerebellum sort of the cerebrum the cerebrum it controls the voluntary actions whatever that you decide to do is controlled by this part here and also it receives and interprets sensations from the sense against like your eye like your ear like your nose it interprets what data or information and also it is the higher thought for it's a higher thought it's responsible for higher thought processes like thinking memory and so forth and then we have got this part here the corpus callosum since i discussed with you guys that the brain consists of two hemispheres the right and the left hemispheres now those two hemispheres that are connected by this part here which is the coppas colossum the copper's colossum its function is to connect the left and the right hemispheres of the brain and also it allows these two hemispheres to communicate with each other remember the rights the right hemisphere controls the left part of the board and the left hemisphere controls the right part of the body now looking at the structure here below the the copper scholar sample above the medulla oblongata is what we call the hypothalamus this structure what does it do it is a control center for hunger for test for sleep for body temperature and emotions this part here it controls it tells you that you are hungry you have to eat if you don't eat now you become hungry and then this patch is going to be stimulated to tell your body to to eat and also when you are tasty it does the same thing it tells your product to drink water it also tells your body to sleep when you are tired or when it's time for you to sleep and then also it controls the body temperature if the body temperature is above normal this pathway is stimulated and once it is stimulated the body temperature is decreased through some processes which we are going to just discuss when we do homeostasis and also it controls your emotions sadness anger frustrations and so forth they are controlled by this part and then now looking at the medulla oblongata the medulla oblongata it transmits impasses between the spinal cord and the brain you see it's between remember here we have uh the continuation of the spinal cord this medulla oblongata is in continuation with the spinal cord and here above it we have the brain so it transmits and passes from the spinal cord to the brain between the spinal cord and the brain and also it controls the actions involuntary actions such as such as heartbeat your heartbeat is not controlled by you it's controlled it's involuntary it's controlled by the medulla oblongata also breathing is not controlled by you you don't decide to breathe in and out your body decides on its own so this part controls that everything and then you've got the cerebellum this part here the cerebellum it coordinates all the voluntary movements such as running that is working so it coordinates all those movements the ones that you decide to do i can decide to run i decide to walk i decide to jump and all those things and then it controls muscle tension to maintain balance now moving forward we have what we call the nerve vs tissue and the nervous tissue consists of a complex system called neurons or nerve cells and those neurons are adapted to conduct or transmit and act to stimulate they transmit information and once that information is transmitted therefore we are going to respond or react to whatever change that occurs in the environment now the first neuron that we're going to look at or the first nervous tissue that we're going to look at is what we call the sensory neuron so these sensor neurons they are unipolar they've got one pole and some are bipolar which means they have two poles and then these sensor neurons they what they always conduct in pulses from the receptor what is the receptor receptor it is the structure that receives the stimuli it is the structure that is stimulated if maybe the change in the environment or case and then it transmitted those impulses from the receptor to the central nervous system which is the spinal cord in the brain for interpretation and then we've got the motor neurons the motor neurons they are multipolar they are multipolar meaning they've got more than two poles and then these neurons have many dendrites you're gonna see those then as when when we look at their structures now the multipolar neurons or the motor neurons they always carry what impulses away from the central nervous system which is the spinal cord in the brain now the difference between the central neurons and the motor neurons is that the center of neuron state always conduct and passes from the receptor to the cns the information is taken to the central nervous system which is the brain and the spinal cord but when it comes to the motor neurons the information is taken away now from the cns to the effect to the structure that is stimulated to remove to respond to the stimuli like your muscles now the connector neuron or the interneurons these ones they connect the node the sensory neurons to their motor neurons connects those sensory neurons to motor neurons in the spinal cord and the brain and also they transmit information as well but the main function is to connect the two the moto neuron and the sensory neuron now moving right along these are the structures that i was just discussing on our previous slides now we're just going to look at the two diagrams now you need to be able to know how to draw these structures because in an exam you might be asked to draw them and label them or they might draw them for you and then you will have to label them and give their function you might be asked like a few questions about them now here we have the motor neuron which is multipolar this part here is what we call the dendrites these parts here they're called the dendrites they take away the information from the cns the information is received by the brain right from the cns and then it goes down this structure here this is what we call the exon all these neurons they have exxon the structure called the exon which transmits an impulse from the cell body to the effect in the motor neurons now these exons they're actually malinated or they're they are covered by a certain sheath now that sheath is what we call the milling sheath now what does it do it insulates what destruction so that it does not lose any electrical impulses this part here now we have got this part here the spaces between these uh structures which cover the exon those spaces is what we call the nodes of renvia these parts here they are called the known of via and then this part here is the muscle and then this muscle is what we call the effector because it's the one that is stimulated to cause movement when maybe you're supposed to move your head away from a hot plate or from a hot surface and then now we have our sensory neuron our sensor neuron it transmits information from the receptor which is this part here maybe the finger tip and then now that information is convected into an impulse in this inside a neuron and then is taken to the cns for interpretation now we also have an exon here which is covered by what the myelin sheath and then this exon now it transmits information from the receptor to the cell body and then from the cell body it goes to the cns and then now we have another important neuron which is what we call the interneuron or the connector neural so this connector neuron it also has an axon but unfortunately the axon of the interneuron is not covered by the myelin sheath and then what you need to also know is that now when you look at the structure when to look at the motor neuron now on our motor neuron we have a cell body this part here is a cell body this part here it's very important it's the cell and then also here we have a cell body which is here this is our cell body here and then also the insulin has got a cell body which is very small it's here this is our cell body this is our support the cell body consists of a nucleus there as you can see they have a nucleus and so forth now you need also to understand how the impulses move along these um um structures now when the information comes now this is the receptor obviously the information is just is received therefore it's going to go down and comes here this is the control center and then it goes and goes it comes here this part is connected to the oh actually we have this diagram here let's just just look at the pathway of the impulses now the sensor neuron it has got them dendrites now this generally attached to the receptor or the structure that receives the estimated now when extremely is received it it goes through these one dendrites and then it goes to the exon which is covered by the mealing sheath for insulation to prevent an electrical loss now as the impulses they are moving or propagating they go to the cell body here which is a very important direction because it controls the processes that are okay here and then the impulse that comes from the cell body is taken away from the cell body by the exon and then it goes and goes and then it goes to the to the international this is the international number two number one is censoring which is similar number two is this insane neuron which connects the two now the information comes here it goes to the brain for interpretation and then it comes back and then it goes to the to the motor neuron now to the motor neuron it this part of the the cyanosynopsis the synaptic nerves of the interneuron they are attached to the dendrites of the motor neuron and then the information or the impulses that transmitted now from the cns they go to the dendrites and then the cell body which is the control center which contains the nucleus and then what happens is that it goes down the exit you see the direction here goes down here towards the effector which is the structure is going to be stimulated to respond to stimuli and then we are going to look at the reflex arc and the reflex action now what is the reflex action or what is the difference between the reflex action and the reflex the reflex arc now the reflex action is a quick automatic or involuntary action that involves the spinal cord and does not involve the brain it is an important function which is to protect the body from harm what happened this particular action it happens so quick and it's automatic which means it's not voluntary so it's not the one it's not you who decides on what to do it decides for you now the reflex act is actually the pathway along which the impulse are transmitted to bring about a response to stimulus during a reflex action this is the pathway this is an action this is what happens when maybe you receive a particular harmful change in the environment now i'm gonna describe what i mean by a particular dangerous or a harmful change in the environment now when you look at this structure you see this person there's a candle there and then there's fire there which produces heat now when you expose your fingertip to this fire what happens because this fire is very hard now this particular place now is called or this particular cycle is called the receptor because it receives the stimuli it receives the heat from the kindle which is in the environment now once the heat is is received the heat it goes into the into the sensitive neuron where it is converted into what an impulse and then that impulse is taken from the receptor it goes and goes right it goes through this part here the dosa um i forgot the dorsal horn is the dosal horn and then it goes it comes into this part is the spinal cord now as it comes to the spinal cord it comes and comes and comes and then interpretation occurs then the spinal cord and then the information is taken from the spinal cord into the interneuron from the interneuron into the motor neuron and then the answer muscle neuron transmit the impulses to the muscles here the effect then you will move your what your fingertip away from the heat because you are getting bent the information has been interpreted in the spinal cord and now your body is aware that you are getting wet bent therefore you need to protect yourself by removing what you feel a tip away from this heat that's it we are done the information goes through the spinal cord via the tonsil hole and then comes back via the it goes into the spinal cord via the dorsal horn and then it leaves the the the spinal cord via the uh the anterior horn the dorsal horn is also called the posterior horn this part here is called the anterior horn it leaves by the anterior horn and then it goes to your effector now what will happen you're going to pull over your fingertip or this finger and then you protect yourself from creating paint and what you need to also discuss this is the spinal cord now the spinal cord has two parts the gray meta which is inside and the white matter outside but in the brain is the opposite the white matter is inside and the gray meter is outside and then in the exam case you will be given this structure and it will be labeled like it's a this is a this is b this is c this is d this part here is d and then this is what e now they will ask for the pathway how is it moving you're going to have to say it starts from a the receptor it goes to b the sensor the neuron which transmits information into the spinal cord and then it goes to the c which is the internal interneuron or the condenser neuron from the conductor neuron it goes to the motor neuron and then from the motor neural it goes to the effect the structure which produces the reaction which responds to the change in this case you want to pull away your your your finger to protect yourself from getting bent that's it that's the pathway it's what the receptor the center neuron the and then from the interneuron to the motor neuron and to the effect that's it now let us look at the peripheral nervous system the peripheral nervous system is all the other nails that are on the periphery of your body they're not at the center of your the periphery of your body is the how can i put it yeah it's the periphery away from the center part of the board remember your your spinal cord and your brain the central part of your nervous system but now the periphery is made up of sensory cells that are that respond to stimuli these sensory cells are called what we call the receptors when the receptors are stimulated or triggered the stimulus is convected into a nerve impulse for estimating to be interpreted it must turn into a nerve impulse guys and then the living pulse is transmitted along the sensitive neurons to the central nervous system that's it the peripheral nervous system is consists of all the nails which they respond to stimuli and they receive the stimulant from the receptors and then we have got the autonomic nervous system now the peripheral nervous system is differentiated into the autonomic nervous system and the somatic nervous system but now what we're going to we're going to discuss is the autonomic nervous system which controls many vital activities in the body or in order to maintain homeostasis we are going to discuss homeostasis guys not now it's a chapter on its own now it consists of nerves which are connected to the hypothalamus of the central nervous system this system con functions involuntarily and automatically it's automatic it's autonomic guys which means automatic now it is subdivided into the sympathetic and the parasympathetic nervous systems that function antagonistically against each other if this other cause possible goes negative if the other one says black the other one says right that is what is meant by anything antagonistically now the sympathetic nerve stimulates organs to prepare the body for action and then the parasympathetic slows down the system and brings the body back to a state of rest now what you need to know is that the sympathetic nervous system is what we call the fights and flight effects is fight or flight is when you are scared or when you are frightened this sympathetic nervous system is stimulated and then it prepares your body for for action maybe in case you are frightened by a lion this sympathetic nervous system becomes stimulated sorry it becomes stimulated once it becomes stimulated you will start finding it prepares your organs for instance now in the sleep is going to prepare your muscles you're going to start running away from the liar and then the parasympathetic nervous system slows down and bring about that and bring the political to a state of rest each again in the body supply to witness from both systems and attempt the double innovation double meaning the body organ anybody again it is innovated by the parasympathetic and the sympathetic nerves to bring about change if one says yes the other one says no and the organs are stimulated a sympathetic part or inhibited by the parasympathetic part of the nervous autonomic nervous system now let's just look at the difference between sympathetic and parasympathetic how do they oppose how do they act antagonistically towards each other now we are looking at the organs and we're gonna look at the sympathetic nervous system what it does and what does the parasympathetic nervous system does the parasympathetic is what we call the rest and digest and the sympathetic part is what we call the flight of fights now the people of the eye when you know to remember this thing you need to give an example like when you are you see a lion coming towards you running towards you obviously a lion is a very dangerous animal you will start to be frightened once you start to get frightened what you do you start running now for you to be able to run to the to a safe area you must see that area therefore your people becomes dilated so that you see clearly okay but not because here you are resting and afraid of anything you're not running to whatever place your pupil is constricted okay so what you can do actually here you need to actually know what is the sympathetic happens the parasympathetic is the opposite of what the sympathetic does and when it comes to the sweat lens what is happening is that you in the stretch secretion is increased especially when it's hot you start sweating to cool your body down but now this one it does not it decreases with secretion for instance when it's cold you can't sweat a lot when it's cold because you're gonna lose so much heat and then you're gonna experience what you call low body temperature which is called hypothermia which is a very dangerous condition your body is supposed to be at a particular state it's supposed to be at a particular optimum temperature once the temperature decreases your body will not function properly and then now the heart rate when you are scared running away from the lion you your heart starts to beat faster why because you need more nutrients and more oxygen to be supplied to your muscles so that you're able to run you need more power to learn so what's going to apply power to your muscles is the nutrients and the oxygen but when you are resting you know the heartbeat just goes normally you don't need any energy because you are resting and you are digesting the food and also the small intestines now decrease peristalsis and blood flow now you can't digest food when you're running you can't eat while you're running that effect you can't so peristalsis is it's being decreased and blood supply is decreased in the small intestines but during parasympathetic nervous system your prosthesis is increased and the blood supply is increased remember guys parasympathetic is a rest and digest so when your digestion or kills peristalsis or cause therefore there must be intense peristalsis so processes has to be increased now the acid is to the skin they are constricted in the sympathetic part pales pale color skin color but they dilate normal skin color and then after this to the muscles they dilate to increase blood flow because which is true so that more nutrients and oxygen yeah they are supplied to your muscles these nutrients are important for production of what you call atp which we did in grade um i think 11 when you did cellular respiration and yeah yeah that's it but they constrict during digestion and rest so to decrease the blood flow less nutrients and oxygen means less atp when you're resting you don't need enough like too much energy guys you need to know just the sympathetic part this part it's the opposite that's how i used to to ace this now bladder it contracts etch to urinate that's why most people when they are scared they urinate but when you are digesting and just arresting it just relaxes sorry guys the blood it sorry yes it contracts so let's urinate but here it doesn't contract it relaxes and then the liver glucagon which is the stored glucose glucose is stored in the body in a form of glucagon so the sort of sort of guy sorry sorry we're going to discuss this one into the endocrine system this is actually a hormone yes which stimulates the release of glucose is sorry guys glycogen is the form of glucose stored in your liver for later use maybe you need energy in future so energy is stored in your body as glycogen and if maybe you don't have energy this glucagon is doing to stimulate what the release of glucose and then also insulin is released released to stimulate the storage of glucose i think guys i need to actually have a video whereby i'm going to explain this because it's really a very complicated chapter now moving right along we're going to look at the types of receptors now we have the entire receptors and these ones they respond to the stimuli from the outside part of the body and are found in the skin the nose the tongue and the eyes and the ears exterior they respond to the stimulus coming from the outside of the body extra efficient means outside receptors you know directions that receives what the stimuli and then you've got the photoreceptors which are sensitive to light stimuli for example the eye photo means but it means i'm light and then chemoreceptors chemo means chemical so this one is sensitive to chemicals such as the such a solution or a gas for example the tongue and the nose and then we've got mechanoreceptors which are sensitive to changes in pleasure such as sound touch sound gravitational stimuli for example the ear the skin the muscles and tendons and then we have got the internal receptors these ones that respond to chemical and physical changes inside the body to maintain homeostasis which is what we are going to discuss right now and then we have got the chemoreceptors here in the aortic arch and the corrupted series are stimulated by the incorrect ph levels of the blood maybe if your ph levels are decreased your your body starts to become very acidic so these receptors they are what they're stimulated and then thermoreceptors these ones are sensitive to heat and cold you know when it's very cold uh outside what happens is these thermal receptors they receive this this the stimuli and then once they receive the stimuli the information is transmitted via the sensory neurons and then it goes to your central nervous system for interpretation and so forth and then to bring about um a change or a response so that you do not and lose so that you do not um shake or shrive shiva because once it's cold is that shivering now what will happen is that uh your body won't release heat outside you want sweat you're gonna maintain the heat inside your body so that the temperature in the body stays at a moderate level gonna discuss that when you do homeostasis and then we've got osmo receptors just insisted to the changes in the osmotic pressure of the blood osmosis we're gonna do that as well i think you did this in grade 11 or 10 if i'm not mistaken i did osmosis and so forth and then you've got the viral receptors which are sensitive to changes in blood pressure they're located mainly in the aortic part now let us just look at our summary guys now the nervous system consists of two parts guides it consists of canvas the central nervous system which is the brain in the spinal cord and also consists of the peripheral nervous system which consists of the sensory pathways these are the names of the neurons the sensory pathways and the motor pathways remember these ones they receive the stimulify the receptors and then they convert the stimulant to an impulse and take it to the central nervous system for interpretation and then the motor one they respond to the changes in the environment now the motor pathways that consist of the somatic one part and the autonomic part this part is the voluntary part this part is the autonomic part this one you control it yourself this one do not control it it happens automatically and then you've got the sympathetic division and the parasympathetic division remember the sympathetic division is what we call the flight of fight and then this part is what we call the rest and digest i think i need to actually make a video of these two nervous types of nervous systems which are under the autonomic nervous system of the peripheral nervous system what you need to know at this moment is that the nervous system divides into two parts the peripheral and the central nervous system and the center divides into the brain in the spinal cord and the peripheral nervous system which is that the system of nerves is made up of the sensory nerves and the motor lens these ones that are systematically transmitted to the cns this one says transmittance and stimuli from the cns to the effector for response and then it is divided into somatic which is valencia within autonomic which is involuntary and then this autonomic is divided into the sympathetic division and the parasympathetic division i thank you so much guys for watching my video and i hope to see you on the next one thank you so much