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0:00
assalamualaikum everybody i'm glad to be with you again in my youtube channel after one year of absence. The topic we are going to discuss in our next presentations is considered to be one of the most important topics in pharmacology because it deals with drugs acting on the central nervous system. The central nervous system as we know
0:31
is the most complex organization of matter Allah created in the universe,
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everything takes place in this system, thinking, feelings, learning, desire, movements, all functions either under conscious or unconscious control take place in the central nervous system. Therefore, I would like to share with you my fascination about the center nervous system.
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In order to start to know the sites and mechanism of action involved in the action of drugs acting on the nervous system, we have to be familiar with certain physiological facts about this system. Therefore this lecture will be a revision of the most important physiological facts about the central nervous system. So, let us start with bism Allah. The main goals of this lecture as I have said is to know the structures and terminology of the central nervous system
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this will include divisions of the central nervous system, we will discuss the different brain parts, especially the most important, we will discuss as well the functions of these parts,
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then we'll discuss the unit structure of the central nervous system,
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and the neuronal communication including stimulation and inhibition of the neurons of the central nervous system. So, let us start with the division of the nervous system.
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The nervous system as we know is divided mainly into two main parts the central nervous system, and the peripheral nervous system. The central nervous system, as we know, is composed of brain which is enclosed in the bony structure of the skull, and the spinal cord which is enclosed in the bony structure of the vertebral column. The peripheral nervous system as we have discussed before in our previous presentations, is composed of the autonomic nervous system
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both sympathetic and parasympathetic, and the somatic nervous system. Of course, as we have said we are concerned with drugs which act on the center nervous system. Therefore we will discuss in details the most important physiological facts about the brain.
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So, first we will discuss the major structures and functions of the brain.
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We all know that the brain is composed of three main parts,
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the first is known as the cerebral hemispheres, cerebral hemispheres, and the brain contains two cerebral hemispheres, one left cerebral hemispheres and one right cerebral hemispheres.
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Second part is the cerebellum, cerebellum. The third part is known as the brain stem, the brain stem, okay. So the brain is composed of three main parts that we'll discuss in a few minutes, the cerebral hemispheres, there are two cerebral and hemispheres, the cerebellum and the brain stem. The outer layer of the cerebral hemispheres is known as the cerebral cortex, the cerebral cortex. The cerebral cortex is formed from elevated ridges as you can see, elevated ridges,
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these elevated ridges are known as gyri, gyri, singular gyrus. Also as we can see there are grooves,
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these grooves they are known as sulci, sulci or singular sulcus, sulcus, okay. So, the outer layer of the cerebral hemispheres is known as cerebral cortex ,
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this cerebral cortex is divided into four different lobes as we can see by the different colors four different lobes. The first is known as the frontal lobe, frontal lobe. The frontal lobe is important in intellectual functions, like thinking, like cognition, like feelings, like behavior,
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As well the frontal lobe is involved in the control of all movement as we will see the frontal lobe is important for the control of all movement. Therefore, the frontal loop is very important for the survival of human beings. Another lobe is known as the parietal lobe, the parietal lobe, parietal loop. The parietal lobe as you can see and we'll see in a few minutes it is involved in sensations, all types of sensations whether it is touch, or pain, or burning, whatever it is,
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takes place in the parietal lobe. Also, the parietal lobe is concerned with speech,
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learning of languages, etc... okay. This is the second parietal lobe, the most important we should always remember that is it is involved with sensation. The third lobe is known as the occipital lobe, The occipital lobe usually is involved in color identification and also vision, so, the occipital lobe is important for vision and identification of different colors
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The fourth lobe is known as the temporal loop, this is the temporal lobe, temporal lobe. The temporal lobe is involved in hearing and as well it shares with the frontal lobe certain functions, like storage of memory, like feelings, like learning as we will see later, okay. Now, the most important that we should remember that the brain is composed of three major parts, cerebral hemispheres cerebellum and brainstem. The outer layer of the cerebral hemispheres is known
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as cerebral cortex, and this cerebral cortex of each hemisphere, as we have said there are two cerebral hemispheres, one right and one left. The outer layer is the cerebral cortex, and the cerebral cortex is divided into four main lobes, each has its own functions, okay. Now we'll talk about the cerebral cortex in more detail because we have to know certain important functions. In the cerebral cortex, this is the cerebral cortex, which we said is the outer layer of the
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cerebral hemispheres, it is known as the cortical area or cortical region, there is a central sulcus, central sulcus,
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divides the frontal lobe from the parietal, as we can see central sulcus, groove central groove, known as central sulcus, divides the frontal lobe from the parietal lobe.
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In front of this central sulcus there is the gyrus, known as precentral gyrus, precentral gyrus, precentral gyrus this one,
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is precentral gyrus. The precentral gyrus there the primary motor area, primary motor area, what does it mean primary motor area? it means that all motor activity is initiated in this area. In this area the body is presented differently, upside down, and the opposite, these all, we will not discuss now
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so in the precentral gyrus, there is the primary motor area. In front of this primary motor area, there is some areas associated with this area which controls motor activity and it is known as the premotor cortex, premotor cortex okay, so
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so there is the central sulcus, and this central sulcus divides the frontal lobe from the parietal lobe, and in the frontal lobe there is the motor area.
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Post central gyrus, in the postcentral gyrus, this one blue, postcentral gyrus this is known as primary somatosensory area, primary somatosensory area, this where all sensations take place the cortex, where all sensational takes place as you will see later, receives information from the different parts of the body, and the identification of the sensation
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takes place in this area. This sensory area in front of it, there is another sensory area which is associated with these primary somatosensory area, this is known as somatosensory association area, okay this is very important. So we expect that any damage in the motor area will result in defects in motor activity, or any damage in the sensory area or the somatosensory area will result in damage of sensations. we have to know that, okay.
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Now, maybe some of you will ask how these brain areas are connected to the different body organs? to the different body parts? We start with the motor area and the motor area is connected to different body regions through what's known as the pyrimidal and the extrapyramidal tracts, the pyramidal and extrapyramidal tracts, The pyramidal tract, as you will see later is concerned with the control of the course movements,
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all motor activity or activity of the skeletal muscle is done through the pyramidal tract
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The extrapyramidal tract is concerned with control of muscle tone, muscle tone tone of the muscle, the increase of activity in the extrapyramidal tract will result in muscle rigidity and vice versa. We will discuss that inshallah when we talk about parkinsonism, okay. Now, so the motor area it is connected to the periphery through the pyramidal and extrapyramidal tracts may be one of the most,
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of the very long neurons are the motor neurons that descend as you can see here, they descend from the motor area, this is the motor area of the cortex, of the cerebral cortex, and this is known as the upper motor neuron, and this will descend through the thalamus and down the medulla, where it will cross to the other side of the body and down the spinal cord to the anterior horn to the muscles. we will discuss that in sha Allah later in detail.
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Most important to remember is that primary motor area is responsible for all motor activities and it is connected to the different body organs through the pyramidal and extrapyramidal tracts. The pyramidal tract controls muscle activity, or course movements, while the extrapyramidal tract controls muscle tone and fine movement
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The sensory area. Of course, I might have to mention that the pyramidal tract is an efferent, efferent tract, efferent means they exit from the central nervous system. The sensory area, receive information, they receive information from the different parts of the body thorough afferent afferent input, afferent means the neurons that come from the periphery towards the central nervous system This is one example, this is an example of course there are hundreds of examples,
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you have the primary sensory area it is connected to different body organs through afferent sensory neurons, we'll discuss that later inshallah when we talk about analgesics, okay. This is an example of a muscle which is connected to the sensory area through sensory input or afferent neurons, okay. So, this is the most important we should remember about the cerebral cortex. There is a motor area that controls motor activity, and there is a sensory area that controls sensory activity.
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this information we will need them later when we talk about different groups of drugs InshAllah. So the second part is the cerebrum, the cerebrum. We have said that the cerebral cortex is the outer layer of the cerebral hemispheres is the cortical area, that cortical area underneath it there is the subcortical area, subcortical area,
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So the cerebrum is the cortical and subcortical structure of the cerebral hemispheres Okay, okay, now it's subcortical structures
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Now, in the subcortical area as well there are very important structures that we have to know
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we need them when we talk about the different groups of drugs. In subcortical area there are many structures like most important are three main structures, the basal ganglia, the hippocampus, the olfactory bulb or olfactory bulb. These three major major structures that I have to remember, okay. So that we can understand. The basal ganglia we need it when we will talk about parkinsonism, the hippocampus we needed when we talk about Alzheimer's disease and its treatment
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olfactory bulb as well we need it in the future. So what's the basal ganglia? The basal ganglia actually it is a complex group of neurons, as you can see all these red spots they are the nuclei of the basal ganglia. So the basal ganglia are groups of scattered neurons
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they are connected together in a certain way to control certain activities. Okay, especially with the muscle activity we will take we'll speak about later, okay now as you can see there are different nuclei in the basal ganglia the most famous is the the caudate nucleus, caudate nucleus as you can see this is very big nucleus ending with the amygdala, amygdala this is another nucleus it is not concerned with the basal ganglia. Also it contains other nuclei like nucleus accumbens
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nigrostriatal pathway, this is a structure of the caudate nucleus, caudate nucleus, okay So, this is the basal ganglia and the basal ganglia is important to us why? Because it controls muscle tone as we will see the extrapyramidal tract it controls muscle tone any defect in the basal ganglia will lead to a defect in movement as we will see later Okay, so the basal ganglia are different nuclei present in subcortical area and they control muscle tone
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we'll take it in details inshallah when we talk about parkinsonism. Now we have to be familiar with the term, okay. Also, they said that the basal ganglia with other structures in the subcortical area they are involved in learning, different types of learning, whether it is habitual learning or conditional learning, or whatever, okay what I should remember in a basal ganglia there are several nuclei present in subcortical region of the brain above the diencephalon as we
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will see and they are responsible for control of muscle tone and some types of learning. The second structure we should always remember is the hippocampus, the hippocampus, and the hippocampus as you can see, there are two of them one on the left side of the brain and one of the right side of the brain. Why we should remember hippocampus why ? we should remember the hippocampus why? because the the hippocampus is responsible for the conversion of short memory to long-term memory
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hippocampus therefore we will expect that any damage in the hippocampus will result in what's known as dementia, loss of memory, dementia, as it happens in Alzheimer's is in Alzheimers, a person does not remember a recent memory
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this recent memory is not stored into long-term memory he will not remember them, okay. So, this is the second subcortical structure we should always remember The olfactory bulb, I will not talk a lot about it it is concerned it is the olfactory bulb is present in the base of the brain above the nose the olfactory bulb above the nose, we would expect therefore that it is involved in sense of smell.
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of course, some smells will provoke happy memories, and some will provoke bad memories but all this takes place in the olfactory bulb okay This is the second structure cerebrum. We talked about the cerebral cortex and the structures of the cerebrum which is telencephalon.
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The third structure we are going to talk about is the diencephalon, diencephalon, the diencephalon, it is a subcortical area which lies immediately above the brainstem
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the diencephalon is the lowest part of the cerebral hemispheres, the cerebral hemispheres this one, it is formed from three important structures that I should remember, the thalamus, thalamus, the epithalamus and the hypothalamus. I should remember as you can see, this is the thalamus, this is the epithalamus, and this is the hypothalamus each one of them is very important for me to discuss sites of action of drugs inshallah in the future.
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For the thalamus all sensory or motor function which comes from the periphery, sensory which comes from the periphery, while the motor which goes from the cortex to the periphery it passes through the thalamus, it passes through the thalamus, so that's why thalamus is considered to be a relay station, they call it a relaying station as you will see later inshallah. A lower sensory neuron will end up in the thalamus,
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and the upper sensory neuron will start from the thalamus to the sensory area
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All we have to know now is that the thalamus is a relaying station for all incoming sensory or outcoming motor activity from the cerebral cortex, Okay. Second about the thalamus, as we can see in a few minutes, it is involved as well in consciousness with sleep and alertness through the reticular activating system. We will talk about that in a few minutes, okay. So, the thalamus is important for certain functions as a relay station
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any damage of the thalamus means that all sensory input to the cortex will not be there i.e. lost
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as well. the thalamus is evolved in the maintaining of consciousness as we'll see.
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Epithalamus I should always remember that it is the pineal gland, the pineal gland which is present
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and the lower subcortical area above the brainstem. The pineal gland secretes melatonin
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that regulates what's known as biological clock, the day-night cycle, biological clock.
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The most important organ I should never forget it's the hypothalamus, this is a very important organ Why? because the hypothalamus controls many of the endocrine functions of the body
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The hypothalamus is divided into 3 main parts, anterior region of the hypohalamus which is very important as we can see
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it is connected to the pituitary gland, pituitary gland called master endocrine gland this is known as the master endocrine gland, this controls all the endocrine functions of the body as we will see later, very small sits just beneath the base of the brain This pituitary gland is connected to the hypothalamus as you will see in a few minutes, okay. So, the anterior region of the hypothalamus controls
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the pituitary gland in the secretion of many hormones like corticotropin-releasing hormone, like a thyrotropin releasing hormone, like growth hormone-releasing hormone, and oxytocin and vasopressin. All these hormones, they control the activity of the pituitary gland. Of course oxytocin
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vasopressin are connected and secreted from the posterior pituitary gland into the general circulation We'll discuss that inshallah when we'll talk about an endocrine system. Therefore, the anterior region of the hypothalamus is very important because it secretes a lot of hormones which controls the pituitary gland activity.
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The middle region of the hypothalamus usually middle region this part, middle region it controls the appetite, there is the satiety centers if the satiety centers are not there people will feel always hungry, satiety center will say stop I have my enough, therefore the control of appetite is through the satiety center, as well growth hormone is synthesized in this area growth hormone is responsible for growth of different body tissue is synthesis in the middle region of the hypothalamus
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The last which is the posterior region of the hypothalamus there is the temperature regulating centers, temperature regulating centers, temperature regulating centers manages body temperature, temperature regulating center, so if any defect in this area will affect the body temperature. Of course, this is done through the autonomic nervous system So, the temperature regulating center is present in the posterior region, okay.
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So, the hypothalamus is very important we should never forget the hypothalamus because it controls endocrine functions, as well, it controls body temperature and and appetite. As we can see the hypothalamus, Insha Allah will discuss it later, this is the hypothalamus it is connected to the pituitary gland through neuronal connection and through blood supply connection. I will not go into details
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because we will deal with it in detail when we talk about the endocrine system drugs acting on the endocrine system
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So, the hypothalamus controls all the endocrine organs they are under the control of the hypothalamus okay. Now, this is the diencephalon as I have told you, diencephalon which is formed from the thalamus, and from the epithalamus and the hypothalamus. So, we talked about the cortical area, subcortical area, and diencephalon. Now we'll talk about another subcortical region that lies in the diencephalon region known as the limbic system, the limbic
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system, the limbic system. The limbic system like the basal ganglia, we should always remember why? because as you can see it has very important functions. The limbic system as we can see it is formed from different nuclei, as you can see, it is formed from the hypothalamus which we already talked about, it is formed from the hippocampus, olfactory bulb which we talked about, from the cingulate gyrus. cingulate gyrus. the septum, the amygdala nucleus, and from the mammillary body
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It is enough to know that the limbic system is composed from different structures, subcortical structures wherewith this limbic system they said that they are important in the regulation of behavior, regulation of behavior is done through the limbic system. General behaviors look like mood, emotions and as well response of body to stress. Of course, the response of body to stress is done through the hypothalamus.
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The hypothalamus as I have said controls endocrine function, and the hypothalamus when the body is exposed to stress whatever it is, the hypothalamus will be activated and the hypothalamus will release and when the body is exposed to stress the hypothalamus will release the corticotropin releasing hormone, and corticotropin-releasing hormone will act on the pituitary gland to
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release ACTH, then ACTH will act on the adrenal cortex to release cortisone, and cortisone levels will be increased. The most important to remember that limbic system is composed of different structures including the hypothalamus, hippocampus, olfactory bulb, amygdala and they are involved in the regulation of behavior. Also a limbic system, it is involved in learning and cognition, especially by smell through the olfactory bulb okay.
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As well in the conversion of the short-term memory of smell and to long-term memories it is involved in memories as well, through the hippocampus, okay. So, this is the limbic system we should always remember. Therefore if there is a disturbance in the limbic system, we expect that the behavior of the person will be changed Okay. Now this all about the cerebral hemispheres, the cerebral hemispheres. The next will be the brain stem, brain stem, the second brain stem
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as we said the brain is composed from three major parts, cerebral hemispheres we talked about them
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and the brain stem and the cerebellum. So the brain stem lies just below the diencephalon this is the diencephalon which we just talked about it, this is the diencephalon. This is the brain stem, this is the brainstem enlarged. The brainstem is composed from three main parts or anatomically it is divided into three main parts, the midbrain, Pons and medulla. Midbrain, pons and medulla. The most important I should always remember is the medulla
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as you will see later. Now, the first part is the midbrain as you see it is this part, is associated with alertness with arousal through the reticular activating system as you will see later
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also, it acts as a relay station between the messages which come from the cortex and goes to the cerebellum, as we will see later inshallah the cerebellum is concerned with the fine control of movement okay posture and etc this is done through the motor area the motor area sends its information to the cerebellum through the pons The pons acts as a relay station will relay messages between the cortex cerebral cortex the motor area and the cerebellum
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and the cerebellum, this is very important function. As well the pons is the origin of many cranial nerves cranial nerves, origin of many cranial nerves like trigeminal nerve, like facial nerve, etc Okay. The third most important part I should always remember is the medulla oblongata is the lower part of the brain which connects the brain to the spinal cord, this is the spinal cord, beginning of the spinal cord, medulla connects the brain to the spinal cord this is one.
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The medulla Oblongata I should always remember it controls the vital functions, what is known as vital functions, like functions of the cardiovascular system, for many of the functions of cardiovascular system they are done in the medulla like for example vasomotor center which we talked about it when we talked about the autonomic nervous system, vasomotor center are centers which control the diameter of the blood vessels, okay
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vasomotor center through sympathetic or parasympathetic nervous system of course. Also, there are cardiac centers, cardiac acceleratory centre or cardiac cardioinhibitory centers, as well respiratory centers are present in the medulla. All these are vital centers, vital centers which lives depends on them there is no consciousness
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If we inhibit the medulla cardiovascular function will be inhibited and respiratory centers will be inhibited, okay. That is very very important when we talk about the general anesthetics, okay. So this is the brainstem what we should remember about the brainstem, most important that the medulla contains vital centers necessary for life, okay. This is the second part,. The first part we talked about was the cerebral hemispheres,
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the second part was the brain stem. The system we are going to talk about is known as the reticular activating system, reticular activating system. The reticular means it is a network activating
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will activate the brain how this is done what is the reticular activating system reticular activating system it is a network of neurons, group of neurons that pass up the brain, pass up the brain stem, pass up the brainstem to the diencephalon and then from the diencephalon to the cortex, to the higher cortical area, to the higher cortical area okay. This system receives sensory information either from the periphery in the form of touch or pain for example or temperature
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and this sensor will pass through the reticular activating system, also, it receives auditory stimulation from the ears, auditory stimulation it receives stimulation from the ears, or it receives stimulation from the eyes, visual stimulation. All these stimulations will go up to the cortex. So what's the function of the reticular activating system? The function is to maintain alertness or wakefulness...
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a person cannot sleep, correct, okay now this is the most important. The reticular activating system main function is to keep the person alert and awake. Of course, if we depress this system a person will go into sleep and maybe unconsciousness for some drugs as you will see later they cause inhibition of the reticular activating system, a person will become less alert less aware and he might lose consciousness, okay.
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This is the first function. The second function which is important as well, this
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reticular activating system will act as a filtration system, filtration what does it mean, it means that many information will reach the system and most important information can pass to the central nervous system to the higher cortical area
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in
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So only the important information that the body needs can pass through the reticular activating system to the higher cortical area, okay. So, this is the second part of the brain which is the brainstem and it's associated reticular activating system
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So, the reticular activating systems they are networkers of neuron that pass up the brainstem to the diencephalon up to the cortex where it receives information from the peripheral efferent sensory input either visual-auditory, touch, pain, temperature etc Its main function is to filter out information from external sources and focus on one particular fact .
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and maintenance arousal and alertness. okay, and this is the reticular activating system and by this, we finish talking about the most important facts about the brainstem. The third part of the brain is the cerebellum, the cerebellum. Cerebellum I will not talk much about it.
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This is the cerebellum, the third part. It is concerned with motor movement cerebellum and coordination and motor learning, the sense of the body position, to know body posture up or down, sense of body position. The balance and equilibrium takes place in the cerebellum. The fine movements coordination, coordination of fine movement takes place in the cerebellum. We expect that any defect in the cerebellum will
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result in motor defect, motor defect, okay. So, this is the third part the cerebellum. Some drugs like alcohol for example produces ataxia, why it produces ataxia? becuase it inhibits the cerebellum activity so the motor coordination of movement will be lost, okay So, this is very briefly the brain, very briefly in the brain The second part of our presentation will be about cell types of the central nervous system
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Actually, there are two types of cells in the nervous system. One is known as the glial cell
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and the other are the neurons, okay. Neurons or nerve cells, so we have nerve cells and glial cells If we talk about the neuron or the nerve cell, usually most of neurons they look the same, Usually, it is formed from cell body this cell body usually contains the nucleus of the of the neuron, and there are branches known as dendrites dendrites, dendrites. These dendrites are the site of interaction with another
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neuron as we will see later, okay, Dendrites, dendrites, one of these dendrites is large enough to form what's known as an axon, an axon, this axon usually terminates in a nerve terminal, in a nerve terminal, and the nerve terminals as we will see later, are the site of storage of neurotransmitters These usually nerve terminals they synapse with another either cell body or neuron, or whatever, or another dendrites in a form of a synapse, this is the synapses, synapses
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Synapse is the space between a nerve terminal and another dendrites or another nerve terminal okay, so this is the nerve cell, this is the nerve cell. Ependymal cells, Ependymal cells this is glial cell, as I have said there are three different types of glial cells this is a glial cell glial cell. Usually, this is the essentials to form or for the formation of the epithelial cells,
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these will lead to formation of epithelial cells which covers the brain cavity, the ventricular cavities of the brain's ventricles. It will cover the cavity of the brain and it protects the brain
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from any insult, okay. The second type of glial cell is known as oligodendrocyte oligodendrocyte is responsible for the formation of the myelin sheath, for the formation of the myelin sheath. The myelin sheath is very important because the myelin sheath will make the conduction through the axon faster as you will see inshallah later when we talk about local anesthetic. you have to know that myelin sheath is produced by oligodendrocyte, okay.
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The third type of cells in the nervous system is known as astrocytes, astrocytes it is also a glial cell glial cell, it is also a glial cell. So in the center nervous system it is either types of cells, in the center nervous they are either nerve cell or a glial cell which might be one of the three
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astrocytes is one of them. The astrocytes is very important because it is concerned with the metabolism which takes place in the neurons or in the central nervous system in general, also it regulates blood flow through the central nervous system and
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most recently they said that astrocytes as well they have their own communication, they act as neurons, they communicate information from one side to another in the central nervous system.
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So these are the type of cells present in the nervous system they are either nerve cells or glial cells and each has its own function. So what are the types of nerve cells in CNS? what are the types of neurons in the central nervous system. Actually there are three types three different types, depending on the functions. The first type is known as sensory neuron
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and as you can see sensory neuron there is cell body, from the cell body branches the axon,
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one right and one left axon, and each will end up with nerve terminals, nerve terminals, usually the sensory cell, the sensory neuron will receive information from one of dendrites and this information will be transmitted to the next dendrites at the end of the cell body, so this is the sensory neuron In sensory neurons usually, a cell body contains two dendrites that branches to form axon. The other type is known as relay neuron, relay neuron. Usually a relay neuron
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is between a sensory neuron and the motor neuron, a sensory neuron and motor neuron called relay neuron Relay neuron as you can see, there is a cell body with dendrites there is an axon but there is no myelin sheath over the axon, there is no myelin sheath Usually, the axon is short, it is not long as it is in a sensory neuron or motor neuron. The third is the motor neuron, A typical motor neuron which is formed from cell body with dendrites one of them will
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form the axon and the axon usually terminates in a nerve terminal. So, these are the different types of neurons. of the neurons which we will see when we talk about drugs acting on the central nervous system Lastly, last thing I will not explain in details because I have done already in a previous presentation that I will give you its address, is the cell communication. How cells are communicated
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together in the central nervous system? As I have said that a neuron communicates with another neuron through a synapse, so usually activity from one neuron is transmitted to the other neuron through the synapse, through the synapse, what happens in the synapse? If we enlarge this area, the synapse if we enlarge it, we find that the synapse is formed from a nerve ending of the first neuron, this is the nerve ending of the first neuron and
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dendrites or the cell body of the other neuron, of the receiving neuron, okay.
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So, in the nerve terminal of the first neuron usually there is a neurotransmitter, a chemical messenger known as neurotransmitter, this neurotransmitter is sensitized and stored in a special storage vesicle in the nerve terminal. When excitation arrives at the nerve terminal, it will lead to the opening of calcium channel, calcium rush in causing exocytosis, a process known as exocytosis, which is the release of the neurotransmitter. This is the
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neurotransmitter molecules. Once these neurotransmitter molecules are released they either act on postsynaptic receptors, or presynaptic receptors, okay.
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So, the neurotransmitter after it is released it will act either on presynaptic receptor which are known as autoreceptors present on the nerve terminal we talked about that in a previous presentation, or act on postsynaptic receptors
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on the other neuron as we have said before. There are three different types of receptors. There are receptors which are linked to ion channels, there are receptors which are linked to G-protein, and there are receptors which are linked to enzyme, enzyme-linked receptor. The details you will find it in this presentation https://www.youtube.com/watch?v=oziRxuiZDrQ&list=PLScGD5JPgadK44N_hdRYctrWKo3yJl8tD&index=6&t=1831s the link of which I will give in comments
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So, the details of this how this happens? how the activation takes place through the activation of the ion channels or G-protein or enzyme and what will be the net result, okay.
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Usually, in the central nervous system most of receptors are linked to ion channels, they are linked to ion channel therefore once the neurotransmitter is released it will open certain ion channels, As we know ions are either positively charged or negatively charged, for example if the neurotransmitter will open positively charged ion channels, like sodium, in this case debolarization or excitation will take place and this is known as excitatory
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postsynaptic potential, excitatory postsynaptic potential. In excitatory postsynaptic potential neurotransmitter will open sodium channel, and sodium channel will cause excitation or debolarization of postsynaptic membrane. The details of this I have covered before in previous presentation please refer to it instead of repeating the same information again. This is very interesting lecture and it will talk about the basics of a neural transmission, okay.
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Opposite, if the ion channels are negatively charged ions like chloride, chloride will enter the cell producing hyperpolarization of the postsynaptic membrane and this hyperpolarization will result in inhibitory postsynaptic potential. This is how communication takes place in the central nervous system. I would recommend you to go back to this lecture in order to know the details of these communication. this is very important lecture okay.
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So, by this I have finished talking about the most important terminology and physiological
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background that we need in our next presentations, okay. So in summary we talked about structure and function of the brain including the brain parts, we talked about cerebral cortex how it is divided into four lobs, what's the primary motor area, and what's primary sensory area, we talked about the cerebrum how it is formed from the cortical and subcortical structure and we talked about subcortical areas like the basal ganglia, like the hippocampus, like olfactory bulb. We talked about
57:33
diencephalon, how it is divided into thalamus, epithalamus, and the hypothalamus and what are the importance of each of them. We talked about brainstem, the mid-brain and pons and medulla. And we talked about the reticular activating system and the limbic system and it's involvement in behavior, okay. We talked as well about types of cell in the center nervous system, whether they are neurons or glial cells, and what are the different types of glial cells. We talked about
58:08
how they are communicated. Our next lecture will be about non-specific CNS depressants and this will include the general anesthetics. So hope to see you in my next presentation
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