hello students today we're going to talk about the brain and the cranial nerves in chapter 14 just make sure throughout the video again emphasize these links for the animations but as far as the principal parts of the brain are concerned the largest mass of the brain is called the cerebrum the second largest mass of the brain is called the cerebellum there is an area called the brainstem which includes three separate parts the medulla oblongata the pons and something called the midbrain there's also the diencephalon which in the middle of the brain which is made up of the thalamus the hypothalamus and something called the epithalamus up here where we also have a gland called a pineal gland which we'll talk about the brain like the spinal cord that we covered in chapter 13 is protected by several structures the brain is as you well know surrounded by the cranial bones part of the cranium and in the skull there are connective tissue membranes that surround the brain as the same ones that surrounded the spinal cord the pia mater the arachnoid mater and the dura mater and then we're going to talk about cerebrospinal fluid and where it's made and where it it circulates in and around the brain so the meninges that surround the brain basically help protect the brain and you can see here in a frontal section of the brain through the cranial the cranium into the cranial cavity enlarged the dura mater is a tough dense outer layer of connective tissue that surrounds the brain and anchors it in the cranial cavity unlike the spinal cord the dura mater and the cranial cavity surrounding the brain is actually made up of two thick layers of connective tissue just deep to that is the arachnoid mater and the arachnoid mater is separated from the Pia mater which is outlined in this little red line that you see here separated from that with this space the space is called the subarachnoid space we then have little extensions of the arachnoid mater that go into what is referred to as dural sinuses this one happens to be what is called a superior sagittal sinus that runs along the top of the brain inside the cranium in the cranial cavity and these structures are involved in reabsorbing cerebrospinal fluid from the subarachnoid space back into venous blood so this will be the venous blood flow up here that will ultimately exit the brain to recirculate in the body there are some important extensions of the dura mater that we should be made aware of first there is something called the falx cerebri this is a connective tissue layer that separates the left and right cerebral hemispheres from one another if we look at a frontal section down here you can see the left and the right cerebral hemispheres a little bit up here and then they're separated from each other by the the falx cerebri the falx cerebellar separates the hemispheres of the cerebellum which is the second largest mass of the brain and then we have something called the tentorium cerebelli right here that helps separate the cerebrum from the cerebellum so these are connective tissue structures that extend from the dura mater that helps separate the parts of the brain from one another the brain tissue itself does not have blood flowing all through the neurons in the neuroglial and tissue in the brain there's something called the blood-brain barrier I think in Chapter 12 if you review that you'll notice one of the neuroglial cells called astrocytes their function was to produce what is called a blood-brain barrier so substances that are in the blood do not have direct access to the brain tissue the astrocytes forming the blood-brain barrier selects what types of substances can pass from the blood to the brain and this is more of a protective mechanism there are three main structures in the brain that do not have a blood-brain barrier will cover those shortly [Music] now since blood does not flow through the brain tissue all of the cells that form the brain tissue which are the neurons and neural glial cells have to get the oxygen and the glucose the ions and other important nutrients that they need to live from what is called cerebrospinal fluid so you can think of cerebrospinal fluid more like the blood for the central nervous system I hate saying it that way but you might understand it a little better that way so we have the blood flowing through our body for all the cells in the body but the brain and the spinal cord is serviced by this cerebrospinal fluid the cerebrospinal fluid is going to carry the nutrients to the neurons and the neuro glial cells and carry their waste products back away out of the brain in this case or in the spinal cord as well so the brain has cavities in it which are called ventricles here you see a transverse plane of the brain over here if we if we cut the brain in the transverse plane and look down into it you can see the middle of the cerebral hemispheres have this Abadie these cavities are referred to as ventricles and inside the ventricles we have special capillary beds that are associated with ependymal cells which is a neuroglial cell involved in a production of cerebrospinal fluid and they're located these choroid plexus e's are located in the ventricles so the choroid plexus contains a special capillaries surrounded by these ependymal cells and the ependymal cells have the job of filtering plasma from the blood and producing the fluid which we call cerebrospinal fluid so as these cells produce this fluid it flows inside of the ventricle so let's look at the direction in which cerebrospinal fluid flows through basically the central nervous system so the choroid plexus sees the blood the capital our blood capillaries with the ependymal cells are located in the ventricles the ones that we just saw from the last picture is called the lateral ventricles they're in each of the cerebral hemispheres here's a sagittal section through the brain so inside inside of here is the lateral ventricle for the left cerebral hemisphere and there would be one for the right as well there's also a third ventricle which surrounds something called the inter thalmic adhesion or in some books it's referred to as the intermediate mass of the thalamus that's a little cavity with with chloraloy plexus in it that's called the third ventricle and then down here is a fourth ventricle just anterior to the cerebellum and each one of these ventricles contains a choroid plexus that produces cerebrospinal fluid now the cerebrospinal fluid is going to flow from the lateral ventricles let me backtrack so here's a lateral ventricle the hole that is in each of the cerebral hemispheres so right at the anterior area of the lateral ventricle is something called the interventricular foramen or foramen a plural so from the lateral ventricles the cerebrospinal fluid flows through the interventricular foramen into the third ventricle from the third ventricle which surrounds the intermediate mass of the thalamus or 2n so that'll make adhesion will flow through what's called the cerebral aqueduct which is located on this picture right here so the cerebrospinal fluid comes out of the lateral ventricle through the foramen and to the third ventricle then it will flow down the cerebral aqueduct which is that the dorsal side of the midbrain which we'll get to in a minute and then into the fourth ventricle so here's the fourth ventricle from the fourth ventricle there's a couple of apertures or holes if you will that allow the cerebrospinal fluid to go into one of two places so from the fourth ventricle the CSF as it's called will go through lateral ventricles and what's called a median aperture I mean the lateral and median apertures through these apertures this CSF will flow into the subarachnoid space which surrounds the cerebellum it surrounds the cerebrum it even surrounds the outside of the midbrain the brainstem and the outside of the spinal cord but the spinal cord if you remember from chapter 13 is hollow there's a central canal down in the middle so cerebral spinal fluid can also enter the central canal so the CSF is actually circulating just on the outside of our brain and on the outside of the spinal cord in what's called the subarachnoid space and it also flows inside the ventricles of the brain itself as well as a central canal of the spinal cord now once the CSF circulates around the brain and the ventricles and around the spinal cord and whatnot and all the cells get the nutrients they need to live all of that used up CSF so to speak with waste products in it is reabsorbed back into a venous blood flow and what's called a dural sinus so this is venous blood flow up here this actually would be the superior sagittal sinus up here and it flows back into the blood via what's called an arachnoid villus or arachnoid villi plural in that way cerebral spinal fluid is always being produced from the choroid plexus circulates around the central nervous system and then it is reabsorbed back into the venous blood flow to go back out to the body so we can get rid of the waste products and then reoxygenate that blood so you just follow this flow chart to help you out with the direction in which CSF is flowing here's a system overview for the nervous system urge you to watch that animation and we're going to get into the parts of the brain so the first part of the brain that we're going to cover is called the brain stem it's actually composed of three sections and if we look on this picture this is an inferior view of the brain so it's like we're looking underneath it we have the medulla oblongata which is right here something called the pons and then an area called the midbrain so we're going to talk about each one of these in turn the medulla oblongata is continuous with the most superior portion of the spinal cord which was obviously covered in chapter 13 so extending from the spinal cord up to where the pons would be which would be right right above here that's called the medulla now the medulla contains a couple of things of interest here number one I'm going to talk about these pyramids these pyramids right here or what we call pyramidal tracts our tracks of motor neurons coming from the cerebral cortex and we still have to talk about that but these motor neurons come down from the cerebral cortex down through our brain ultimately to enter the spinal cord and they control skeletal muscle function but notice in the medulla a large number of the bands or tracks from the pyramidal tracts cross over each other from the left side of the brain to the right side of brain and vice versa there's a few that run down the same side of the brain from which they originate but about 85% of the axons cross over in the medulla at an area called the decussation of pyramids so this decussation of pyramids are crossing over here is of some interest because ultimately the right side of your cerebrum controls the left side of your body skeletal muscles and the left side of your cerebrum controls the right side of your body skeletal muscle so basically your right arm and leg is mainly controlled by the left cerebral hemisphere and vice versa which is of some interest there so we have the pyramidal tracts we also have the inferior Oliveri nuclei which are involved in particular reflexes that help coordinate muscle can scale to muscle contraction but overall there are special centers in the medulla that we get into in a little more detail in anp2 but located in the medulla oblongata are the Centers that regulate cardiac activity regulate respiratory activity is involved in vasoconstriction which is a decrease in vessel diameter swallowing coughing vomiting and sneezing and hiccuping reflexes are also all initiated from the medulla oblongata the pons is superior to the medulla it's a little bit larger than in medulla oblongata and it actually links various parts of the brain to each other it contains sensory neurons coming in and motor neurons coming out which they don't really show we'll talk about the reticular formation in a minute but it's a major relay area so is the medulla tracts coming in tracts coming out from the various parts of the brain that we have to talk about so the pons ultimately controls several different things but it's involved in skeletal muscle movement helping coordinate the information to and from the cerebrum to the cerebellum to allow a coordinated skeletal muscle action in our body and we'll talk about that coordination when we do the cerebellum in a minute but along with the medulla oblongata the pons also contains some centers that are involved in controlling respiration the midbrain is just superior to the pons it's actually made up of at the dorsal side of it something called the tectum which is the roof of the midbrain the roof of the midbrain contains four little nodules of nervous tissue those nodules collectively together are referred to as the corpora quadrigemina Quadra because there's four rounded elevations two of them are superior elevations and two of them are inferior so they're referred to as a superior colliculi and the inferior colliculi the superior colliculi are involved in the reflexes that process visual stimulation so reflex is associated with visual sensory input is controlled by the superior colliculi and the inferior colliculi regulate reflexes associated with auditory stimulation or when you're hearing something so for instance if someone comes up behind you and claps their hand real loud and you didn't know they were there you probably would turn around real quick that noise that you hear and the action of turning around is partly initiated by the inferior colliculi rather the superior colliculi would bring about reflexes similarly but would be associated with visual inputs so if you saw something that startled you you would react to it due to the superior colliculi and then we have this pineal gland that lies at the superior portion of the superior colliculi we're going to talk about that in a second so the midbrain itself contains some structures referred to as the cerebral peduncles you can't see them from this picture because this is the dorsal view of the picture the cerebral peduncles can be seen from the anterior view of the midbrain and they are shown here but this is in a transverse plane so if we were looking at it from a transverse plane these are called the cerebral peduncles the cerebral peduncles coordinate the movement or really the transmission of motor and sensory impulses back and forth to different parts of the brain and then we up and down the spinal to and from the spinal cord and then we talked about the core blood corpora quadrigemina already this is that name I was referring to with the four rounded elevations called a superior and the inferior colliculi so the midbrain conveys motor impulses from the cerebrum to the cerebellum and to the spinal cord as well as sending sensory information from the spinal cord to the thalamus which we have to talk about and regulates auditory and visual reflexes ultimately because of the corpora quadrigemina remember the superior colliculi are for visual reflexes and then the inferior colliculi are for auditory reflexes and we'll talk about the thalamus and what it does here in a second now the reticular formation which extends through most of the brainstem and obviously you can see here it's taking up some of the medulla the pons and into the midbrain the reticular formation is composed of neurons that transmit information to the cerebral cortex about sensory signals that you may be encountering so there's a sensory input to the cerebral cortex from the reticular formation it's also the part of our unconscious brain which I forgot to mention the brainstem is our unconscious brain as well as a cerebellum so the reticular formation is involved in helping you stay awake maintaining consciousness or in the morning when you are awakening from sleep the reason why you wake up is because of signals from the reticular formation so I put in throughout the PowerPoint these slides that show the parts of the brain with their functions so you need to make sure you go through where I have these and just review their functions as I'm not mentioning every single function what I want you to know will be in these particular locations on these slides the medulla oblongata the pons and the midbrain all make up what is called the brainstem so know those parts and their particular major functions the cerebellum is the second largest mass of the brain it located in the inferior and posterior part of your cranial cavity it is made up of two hemispheres there called the cerebellar hemispheres we have a left cerebellar hemisphere and a right cerebellar hemisphere and in between them is something called the vermis that separates them just deep to that is the foul cerebellar that I was mentioning before which helps separate partially the cerebellar hemispheres from one another now the cerebellum is are also part of our unconscious burning we don't have conscious control from our cerebellum some of its major roles involve skeletal muscle coordination the maintenance of muscle tone your posture and balance so ultimately we have signals that come from our cerebrum which I want to mention in a minute that directly control skeletal muscle contraction but information about those skeletal muscles contracting is rerouted to the cerebellum and the cerebellum runs a checklist if you will was the muscle that was contracting generating the appropriate reflex or not or do we need to make adjustments in muscle contraction in order to maintain posture and balance consider this if you're walking down the street and all of a sudden you didn't see a pothole and you step into it and you look down and you're already stepping into it you automatically have a reflex to adjust your muscles so that you don't fall now we know that doesn't always work but you will adjust muscle contraction to try to prevent you from falling because your intended muscle contraction was just a walk straight it wasn't to walk into a hole so our cerebellum is involved in that coordination if that makes sense to you the cerebellum also has white matter and gray matter as does the cerebrum which we'll talk about the white matter if we look this transverse mid-side I'm sorry midsagittal section of the cerebellum the white matter inside a cerebellum is referred to as the arbor VT the arbor VT is the white matter so that's all myelinated neuron parts and then the gray matter extends into the cerebellar cortex and the cerebellar cortex has all of these miniature folds in it and these miniature folds are referred to as folia so the the cerebellar cortex contains all of the gray matter which obviously is unmyelinated neuron cell parts the diencephalon is a box in the middle of our cerebral hemispheres it's made up of three things something called the thalamus below it is what we call the hypothalamus and then I know they don't show but right well they do show it right around the posterior to the superior portion of the thalamus is what's called the epithalamus and that is where the pineal gland is located so we have to talk about these three parts of what's called the diencephalon and again the diencephalon forms a box in the middle of our cerebral hemispheres so here's just a little graphic you don't have to identify anything on these pictures I used them just to show you where the structures are located but you see they projected to the surface of the cerebral Hemisphere this is a cerebrum we haven't talked about it yet and deep to in there is what we call the thalamus so here's a midsagittal view they took off the right cerebral hemisphere and there would be one of the loads of the thalamus with the inter thalmic adhesion or sometimes called the intermediate mass of the thalamus so here's what the thalamus looks like it's made of these two lobes or left lobe thalmic lobe and a right thalmic lobe that are interconnected by this inter thalmic adhesion or the intermediate mass of the thalamus the thalamus is superior to the midbrain and it serves as a major relay station for all sensory input all the sensations you can think about that that you would feel and even some unconsciously perceive sensations that we haven't talked about are processed through the thalamus except for olfaction or the sense of smell that's the only sensation that is not processed through our thalamus so the thalamus is a major relay station for our sensory inputs there are also some motor outputs that are important dealing with the autonomic nervous system that come from the thalamus and down to what's called the hypothalamus the hypothalamus are collections of nuclei down below the thalamus so here's a thalmic load this would be the left thalmic lobe embedded in this left cerebral hemisphere here's the intro Helmick adhesion or intermediate mass of the thalamus right here the hypothalamus has four major regions that's all involved in controlling reflexes that regulate almost all homeostatic conditions in our body so we're not going to go over all four of the major regions of the hypothalamus but we're going to learn what the hypothalamus does in general all right so before I show you that slide with the functions on it let's talk about the epithalamus the epithalamus live superior and just posterior to the thalamus so here's the thalmic globe the EPI thalamus is up at the top and extends downward a little bit to the posterior section of it the epithalamus contains the pineal gland which produces melatonin and you may have heard of that before you can buy melatonin as a supplement as a sleep aid so melatonin is a hormone it helps set our biological clock which is referred to as a circadian rhythms we talk a lot more about that in a and p2 but for now you just know that it basically is a hormone that globally sets our cycles of activity and our cycles of rest which is called our circadian rhythm that the Haven Ehrlich nucleus is also located in the epithalamus down here and is involved in the sense of smell which is olfaction now there are three important areas around the diencephalon that do not have a blood-brain barrier these three structures collectively together are referred to as the circumvent Rick Euler organs because they circle around the ventricles that around the diencephalon so the circumvent Rick Euler organs are around the diencephalon since they lack a blood-brain barrier they also are very important in monitoring chemical changes of the blood that can help initiate reflexes like respiratory reflexes cardiovascular reflexes to maintain homeostasis in our body so these organs are involved in both endocrine and nervous system reflexes and they include the hypothalamus itself the pineal gland and the pituitary gland so all three of these structures are involved in maintaining and regulating the reflexes in the body initiated by the endocrine system which is a system of hormones in the body and nervous system reflexes so here is a chart that shows the three portions of the diencephalon again review them for their functions and know that the diencephalon is made up of the thalamus hypothalamus and the epithalamus now let's get to the largest mass of the brain the cerebrum the cerebrum is composed of two cerebral hemispheres there is white matter and there is gray matter the gray matter of the cerebrum is located in what's referred to as the cerebral cortex contains a billions of neurons associated with the gray matter and the cerebrum can be divided in two certain regions and structures for instance the cerebrum has folds in it that project in and outward the folds are referred to as Jerry that's plural gyrus would be singular there are fissures or separations between parts of the brain that little areas that separate one gyrus from another one is referred to as a sulcus or Saul si plural and some of these can be identified on the brain now deep to the cerebral cortex is where the white matter is located the white matter are tracks of myelinated neurons that connect each part of the brain together and the brain to the spinal cord directly there's a deep connection between the cerebral hemispheres called the corpus callosum that connects the right and left cerebral hemispheres together if you look at this graphic you can see the gray matter on the outside of the cerebrum this is referred to as the cerebral cortex this actually makes up our conscious brain and we'll talk about that in a second we have fissure which separates the longitudinal fissure in this case that you see right here separates the left cerebral hemisphere from the right cerebral hemisphere the gyre er these folds that we see in the cerebral cortex and a little separation that goes down between each gyrus is called a sulcus the cerebrum itself is separated two lobes the frontal lobe appear the parietal lobes the occipital lobes and the temporal lobes which we can't see from this view because we're looking at a superior portion of the brain so here's here we see it much better the frontal lobe the parietal lobe occipital lobe and the temporal lobe so each lobe contains special sets of neurons which are involved with controlling different aspects of our body and we're gonna talk a little bit about that where you see things smell things tasting stuff like that we're gonna talk a little bit about the insula is deep to the cerebral cortex and each cerebral hemisphere they the artists of this picture kind of projected it outward so we can see it but it really is covered up by the frontal parietal and the temporal lobe here's a real picture of the brain a sagittal view of the massager overview of the brain white matter tracks right here the the gyri of the brain with a sulcus right here the this is the cerebral cortex where the gray matter is located this is where you think you learn you control things consciously all from you feel things all around the body this is where you feel and manipulate you learn all of that consciously this is our conscious brain the cerebral cortex now the basal nuclei are basically areas of gray matter that are embedded in each cerebral hemisphere they have multiple functions dealing with coordination some emotional aspects as well for various types of feeling but you see what where the white matter is located right here these darker areas are referred to as well these gray matter areas are referred to as some of them as the basal nuclei the limbic system is also embedded areas of gray matter you can see they have numerous names like the parahippocampal gyrus the amygdala these are two fairly important ones the olfactory bulb and tract you see here the corpus callosum contains tracks and the sync cingulate nucleus right here all of this just to make it as simple as possible some of these gray matter areas of the limbic system is what we call our emotional brain and this is where we register certain types of emotions so let's talk about the cerebrum a little bit more and we'll get back to the limbic system in a minute so the brain the cerebrum I should say the cerebral cortex is functionally organized to control specific inputs and outputs for instance there are sensory areas in each one of the cerebral Hemisphere one of the cerebral lobes that's involved in detecting particular type of stimulation for instance vision is in one place auditories and another one smell so forth and so on the motor areas are also located in the cerebral cortex involved in initiating reflexes that I'll mention here in a second and then excuse me association areas that allow us to make sense of sensory inputs for particular pieces of information so if you taste if you eat an apple and you didn't know you're eating an apple and it tasted like an apple you would picture an apple in your head there's an association area that allows us to make those connections so the association areas make connections so we can understand what is going on in our environment so you don't have to go and learn all of these areas of the cerebrum and what happens in them there's a couple of areas of importance here number one up here by the parietal lobes we have what's called a pre central gyrus and a post central gyrus this is the central sulcus in the middle and the precentral gyrus is referred to as our primary motor area the primary motor area is the area in that and of course the cortex of the gyrus is the area where we generate motor information to go out to the skeletal muscles in the body to allow them to contract so all of your skeletal muscle contraction that information comes from the primary motor area the post central gyrus is what is referred to as our primary somatosensory area so the primary somatosensory area is the area where we actually feel many types of sensations like if you stick your finger with a needle it hurts and you feel it you're gonna feel it in a primary somatosensory area for the some for your somato sensory inputs all right now the occipital lobe is where we have our primary visual cortex so you're actually seeing this power point at the back of your cerebrum at the occipital lobe the temporal lobe contains the primary auditory area and so we can hear we know we're hearing something from the primary auditory area in the temporal lobe and then we have what's called the Broca's speech area which is located in the lower parts of the the parietal lobe and just at the area of our frontal lobe the Broca's speech area is the area which allows us to actually form words so typically if someone has a stroke and it affects this area of the brain the Broca's speech area they can understand and you when you are speaking to them but they can't form words correctly to communicate back to you when this area is damaged alright so here are just some basic functions of the cerebrum just you know go over this is pretty generic but when I mentioned the limbic system earlier the limbic system basically registers and promotes reflexes for various types of emotion which include pleasure pain docility affection fear and anger these types of emotions are registered and reflexes associated with them or registered at the limbic system now I left this slide in here just so you could go and look at I don't know if you ever heard of somebody saying I'm right brained or left brained I'm not going to necessarily put this information on our test but I left it in here so you can go and review it because it is somewhat interesting about right brained individuals and what goes on in the right brain like music and artists have a well-developed right cerebral hemisphere the left brain individuals are more into logical and scientific and math and all of that so left brained individuals or right brained individuals that some people have the best of both worlds they have really developed areas in both the right and the left cerebral hemispheres so you just review that for your interest now the last thing that you're going to be covering in this chapter are the cranial nerves I know there's a lot of information on the cranial nerves but I just want to let you know that you need to know the 12 pair of cranial nerves by name and number and the numbers are Roman numerals there are 12 pair of cranial nerves right so I have a couple of these tables with the information that you need and you need to know if the cranial nerve has sensory neurons in it which means they have a sensory function and sensory neurons obviously carry information into the brain or if they have a motor function and a motor function obviously is where the neurons are carrying information or action potentials away from the brain and then some neurons have a mixed component where they have some neurons that are sensory and some neurons that are motor so some neurons are carrying information in and some are carrying information out so I want to know which ones are sensory which ones a motor and which ones are both and their principal function for instance the first cranial nerve is the olfactory nerve it's involved in the sensation of smell cranial nerve number two the optic nerve is involved in vision so forth and so on so I want you to know the functions from these tables so here are the first eight cranial nerves here are the nine through 12 with their name and their number so you again you need to know their name and number you're gonna have to know this for your lab if you're taking a lab anyway if it's a sensory or motor and what their principal function is now put in here a mnemonic which is in your book but you can look any number of mnemonics up to me remember the cranial nerves this one is ooo to touch and feel very green vegetables ah and the first letter on each one of those words is the first letter of the name of the cranial nerve one that I learned when I was in your place a long time ago is kind of silly but you know I still remember it to this day I thought the instructor was kinda silly with it but now see if I could remember it goes on old Olympus towering towering tops let me start over on old Olympus towering tops a fin view Germans viewing a hawk so I know that's kind of silly but you know what I still remember it so you can learn any number of mnemonics to learn the number and the name of the cranial nerve I just need you to learn the last things that are in the PowerPoint are links to go and look at animations so here's one for the overview of everything that we covered and then I have one for each one of the cranial nerves all the way down the cranial nerve number 12 so you whoops sorry about that so you can go and review those alright so if you have any questions email me and I will get back to you as soon as possible and good luck studying