 Welcome to today's lecture where we're going to be looking at chapter 23 of the nervous system So getting started with the basics when we talk about the nervous system We're talking about both the brain spinal cord and all the nerves that come out from that central portion Along with those we have the sense organs like our tongues nose ears eyes So our ability to smell taste hear see and feel and the way the nervous system is going to communicate Which we saw in the muscular system is going to be through these chemical messengers called neurotransmitters or neuro for nervous system and Transmitters are going to be the chemicals that are Communicating with the other either parts of the body or other neurons to transmit signals So then looking at the basic physiology There's going to be basically two major components and then the brain is going to be responsible for Figuring out what to do with them. So the first one we're going to look at is sensory input So when we talked about those five senses of the body, there's going to be specialized neurons all over that are going to Respond to the stimuli from within the environment. So as that stimuli Activates those nerves, we're going to send a signal up to the spinal cord and into the brain And once that information gets to the brain the brain is going to interpret what those signals could possibly mean So within that brain and spinal cord We're going to interpret that sensory information and this is what we're going to kind of call perception So what are we going to do now that we have this information and the brain is going to be the ultimate? Generator of our experience This information doesn't mean anything until it really gets to the brain and the brain decides How to respond and it's within that response that we're going to call motor output So we saw this with the muscular system where we move our skeletal muscles and that could be one response That's generated, but motor output can also have to do with what the glands or other organs of the body do as well So basically the motor output does everything that the body demands of it and then on top of these Initial three when we usually think about the brain, especially with humans or a higher order animals We're talking about higher mental functioning. So when we say cognition, that's basically our ability to think plan ahead See things in the future Our memory and our emotional response So there's going to be specific areas of the brain in which these processes occur and these areas of the brain are only going to be Available in certain species where lower order animals Their higher mental functioning is going to be diminished compared to something like a primates or humans So when we break the nervous system down then into different regions, we're going to have both a central and a peripheral So when we talk about the central nervous system, we're talking about the areas of the nervous system located in the center body So the brain here and then the spinal cord going all the way down the media Aspect of the body. So when we say the central nervous system, we're talking about the brain and spinal cord brain and spinal cord only And because it's so important if anything were to happen to the central nervous system There'd be severe diminishing function. So we're going to surround it by a protective bony structures like the skull or the vertebral column Again, the more we can protect the better because there is going to be other differences between the central and peripheral nervous system And one of the major ones that we'll see with some pathologies is when the central nervous system is damaged It doesn't have the ability to repair itself like a peripheral nerve does so when you see people with spinal cord injuries You generally don't see a lot of Recovery because the central nervous system doesn't have the capability to repair itself like other nerves of the body This is slowly changing as the research progresses But the general rule especially back in the day was any injury to the central nervous system is going to Be pretty absolute and doesn't feel very well So here we can see just the posterior aspect of the central nervous system And then going along with the central all the nerves that come out from that central spinal cord and brain We're going to term the peripheral nervous system again peripheral meaning out to the side the peripheral vision Is what you see out to the side same thing with our nervous system So everything that all the nerves emerging from that central nervous system will consider peripheral So they can either come directly out from the brain, which we'll call cranial nerves or they're going to come out from the Spinal column as well. So all these white fibers you see here are going to be what we consider the peripheral And it's within this peripheral nervous system that we can divide it up even into smaller Subdivisions the somatic nervous system and the autonomic nervous system. So let's take a look at both of those So if you remember when I said whenever you see the term somatic, soma is going to mean body So we're going to be talking about what's going on. So in this case The somatic nervous system is responsible for transmitting signals to the skeletal muscles So when we looked at that neuromuscular junction, we were talking about the somatic nervous system And the key thing I want you to know about this is that it's going to be mostly voluntary So when we choose to move our body or contract our skeletal muscles when we say it's voluntary It means that we have conscious control over what actions we perform So the exception is going to be with those reflexes like when we saw that patella reflex You hit the tendon with the hammer and you automatically kick. We didn't have to think about kicking So the reflexes are going to be the exception to that rule the somatic nervous system So as opposing the somatic nervous system, we're going to have an involuntary part of the peripheral nervous system called the autonomic nervous system And again, this is easy to remember because you can just think it's like an automatic part of the nervous system And this is going to be important for organs or parts of the body that we don't want to have to always consciously think about controlling So all their organs like our hearts and lungs, we don't have to think about every time they beat or every time we breathe in So the autonomic nervous system is going to control those functions for us So we're going to consider the parts of the an s mostly involuntary with the exception being breathing I can make myself breathe in and out voluntarily if I want to but if say I were to hold my breath and I'm Not taking any oxygen anymore The brain's going to take over make me pass out and then once you pass out from holding your breath The brain's going to take over and start breathing again for you So it's kind of a little fail safe to make sure you don't do anything too stupid And here in this picture you can kind of see some of the parts of the Autonomic nervous system if we zoom in a little bit Here you can see all these white fibers that are going around Are going to be part of the autonomic nervous system So you can see how they're wrapping around all the organs of the body the heart liver stomach General areas all part of the autonomic nervous system And then we're going to break the autonomic nervous system town into two more subdivisions The sympathetic and the parasympathetic and these are going to be very important for our massage therapy because our job as massage therapists Is try to get the body to calm down and it's going to be the autonomic nervous system That's responsible for our stress states So we're going to first look at the flight or flight system known as the sympathetic nervous system And this is going to control our energy expenditure. So usually you think of this as our stress response But what it really does it's going to Prime the body to get ready to expend energy to try to either run for its life or fight for its life So the stress hormones like adrenaline or noradrenaline or epinephrine and norepinephrine Are going to be a major component of this sympathetic nervous system And we're going to look at this much more closely when we talk about the endocrine system next chapter So I think a good example of this fight-or-flight response that I see Every month for the pride of the rest of my life is going to be the dreaded words Emplex I've seen this create more stress in my students than any other thing so far Yes, it's terrifying the terrible emblem And then counter to the sympathetic nervous system We're going to have the part of the a and s that's We call the parasympathetic and opposed to fight-or-flight. It's going to be the rest and digest So if the sympathetic nervous system was responsible for energy expenditure The parasympathetic is going to be responsible for building those stores of energy back up So it's going to control our energy conservation and as massage therapists. This is the part of the nervous system We're trying to engage we're trying to get the body to relax And I know you guys haven't had a lot of experience massaging each other too much But it's very common to hear say someone's stomach rumble during the middle of a massage And that's a good sign as a massage therapist because that lets you know that the body has engaged that parasympathetic system And they're now digesting and building back up their energy reserve. So that's where you want your clients to be And it's very easy to do So then taking a look at what the point of the autonomic nervous system is if we look at the parasympathetic Parasympathetic branch first we can see there's going to be a whole host of Things that that's going to do to the body So starting at the top the pupils will constrict Because it has to do with digesting you're going to see the whole digestive system starts to be engaged So that's going to be an increase in saliva production Your heart rate is going to reduce and relax your blood there bronchi and the respiratory system are going to constrict And your whole digestive system is going to be stimulated. So digestive organ activity goes up pancreas liver gall bladders are stimulated Bladder is going to constrict and you can Get stimulation of the genital area. So stimulation or erection of the genitals in a man or woman and as massage therapist It is possible for someone to become aroused on your table And it's important to realize it's not always an overt sexual thing It could just be a part of the parasympathetic response. So if that does happen You just have to kind of ignore it Unless there's other signs otherwise, but it is a possibility that it's just a responsive nervous system that they're relaxed Looking at the sympathetic nervous system then or the fight or flight We're going to have the opposing actions So this is going to help explain the stress response that we sometimes see in people So the pupils are going to dilate and when you think of fight or flight, you're thinking of that Gazelle trying to escape the lion on the serengeti What's their body have to do to try to get them to survive? So when we say their pupils dilate the larger your pupil is the more Light information you can take in so the more acute your vision is going to be So you want your pupils to dilate so you're more aware of your surroundings to be able to spot that lion because Digestion has nothing to do with survival in the moment. We're going to shut that entire system down So your mouth is going to get dry And you're not going to be able to swallow as easy Your lungs and respiratory system the bronchi are going to dilate So your body is preparing to expend a lot of energy and that means you're going to have to run long and for Very fast So if your bronchi dilate that means more oxygen and more air is going to be able to enter your system And that's going to help the fuel your muscles to escape Same thing with your heart rate is going to rise So you're going to be a better pump that oxygenated blood to the muscles to use them And again, all the digestive systems will shut down It's going to stimulate the adrenal the adrenal glands to release their stress hormones to keep this system going And somewhat stereotypically Your urinary bladder is going to relax and this means the sphincter You could just end up peeing on yourself. You see this a lot with animals if you scare them They're just going to like either pee in your hand or just pee right there So this is the same thing that's going to happen with humans If you stimulate that fight or spite stress response, you're going to have an initial urge to go to the bathroom Whether that's urinate or defecate So sometimes when I give out really Serious tests, you'll see some people go to the bathroom right beforehand And that's because their autonomic nervous systems kick in and they're extra nervous about the test Taking a little bit closer look at the brain then It's going to very roughly around three pounds three pounds in an adult But it's going to have very high energy demands. So even though it's only three pounds, which is about On average two percent of the adult body weight. It's going to use up to 20 of the body's energy So it's very high Demand because it's constantly functioning whether we're awake or sleeping The neurons within the brain are constantly working and all that All those action potentials all that firing It's going to take ATP. So it's going to need a lot of energy to function properly And because it's important we're going to surround it by a blood brain barrier And what a blood brain barrier is it's a semi-permeable membrane that's going to keep out many chemicals and pathogens So the worst thing that could happen would be is if we got a bacteria or virus within the central nervous system It would easily disrupt the functioning of the nervous system. That would not be good for survival So to kind of add an extra layer of protection We put this blood brain barrier So we can see the blood on the outside here brain on the inside here And there's this extra barrier that's going to help filter All the kind of solutes within the blood to prevent them from either coming in Or to double check them to make sure they're allowed in and this is going to be important Why it's so hard to treat certain diseases of the central nervous system because a lot of drugs that work in other parts of the bodies The molecules are going to be too large or not just right enough to fit to get through this blood brain barrier So there's kind of like a privileged site in the brain that a lot of drugs can't get into So that's part of the reason why drug discovery with neuroscience can be difficult Is getting drugs that can pass through this blood brain barrier Looking at the different regions of the brain then there's going to be four major ones that I expect you guys to know for the test So we're going to start with the outermost part called the cerebrum And this is the largest most superior portion of the brain and when we talked about that higher mental function This is what's going to all occur in that cerebrum. So typically when you see the brain like here all these folds and crevices and Ridges that stick out. This is the cerebrum that we're looking at in particular It's the cerebral cortex if you remember cortex means The part of an organ that's on the outside So the cerebral cortex is a thin gray layer covering the outside of the cerebrum and you're going to constantly see The reference to gray matter and white matter So when we talk about gray matter, we're talking about the cell bodies. So here we can see This gray matter on the outside of the cortex there And then opposing the gray matter is our white matter Here you can see in white and anytime you see white in the nervous system It means that we're looking at the axons in particular These are going to be axons that have a special fatty covering to them. So in the case Of this nervous system anytime you see white We're the tick talking about fatty tissue called myelin and that's going to help transmit signals At a better a faster pace And you'll also notice that there's this thick line going down the center of the brain And this is called the corpus callosum and this is what's going to connect both the right and left hemispheres of the brain A lot of times you'll see different things about Hemispheres Having different functions one way or the other. There's some truth to them. We'll go over just the kind of More Accepted ones but in general a lot of the popular science stuff you see about left and right hemispheres Isn't so much based in or grounded in well-known science But here we can kind of take a closer look at the corpus callosum This is from an image called defense Fused tensor imaging and this is looking at those white matter tracks So you can see all this white matter or all these axons And it's these axons that are going to go from left to right hemispheres And that allows the two hemispheres of the brains to communicate with each other When we finally meet back up I'm one of my favorite experiments to talk about and I'll show you guys some videos Is of the split brain patients where because it had terrible seizures. We didn't really have a treatment for them Especially back in the day. So one of them was to sever the corpus callosum And what this does is it stops the transmissions of those Signals that are causing the seizures, but the same times they these patients now can't communicate The two sides of their brain and it's basically having two functional different brains in the same person so Kind of on the surface, you don't always notice something different, but certain tests are going to really point out Uh What happens when the two parts of the brains can't communicate in some cases their right and left hands Don't want to cooperate and this is leads to something called alien hand syndrome Where say one hand is trying to button someone's shirt and the other one's going to be unbuttoned at the same time And this person's not going to have any control over that And we'll kind of look more into What that means overall So when we say the left hemisphere If you take anything away from the left hemisphere It's that it's going to be responsible for language So our ability to understand or to communicate is going to be based in certain areas of the left hemisphere So that's both receiving and expressing language As far and also know that the way that the brain works is it's going to control the contralateral side of the body So the left hemisphere is in charge of controlling signals to the right side of the body So when I raise my right hand, it's a signal from the left side of my hemisphere the left motor cortex But so then if I raise my left hand, that's a signal sent from my right hemisphere And the only thing I've been really comfortable saying about the right is that it's involved in spatial relationships so your ability to kind of Either read a map or navigate a three-dimensional environment seems to be located more in the right hemisphere And there's some other things associated between the right and left, but that's not really important for our class So in looking at the different parts of the cerebrum, we're going to be divided into lobes And you'll notice just looking at this picture here They're going to be named after the parts of the skull and what you're there found So when we talk about the frontal lobe Found beneath that frontal bone or the cranium This is going to be responsible for the cognition so our ability to reason and plan Um and our voluntary motor output so the motor cortex is going to be around here And when we talk about the ability to reason and plan, uh, this is the Basically the frontal lobe is going to be like the last part of the brain that kind of comes online So when they say that people Don't really mature until say the age of 25 What they're saying is that their frontal lobe hasn't fully formed all the connections yet So this is why you see in a young kids or teenagers Their ability to kind of think ahead and plan for the future and not do something irresponsible A lot of that is going to be because their frontal lobes haven't fully developed And they just haven't really thought through everything where someone say over the age of 25 Their ability to reason and plan Is more developed This is why also you see people with brain damage, uh, they kind of lose their impulse control Is what they'll call it The pridal lobe then, uh, you can think of sensory input sensory input is going to go all over the place But when we say sensory input, this is where you'll find that somatosensory cortex that we just learned about right in here The temporal lobe then has to do with hearing and language Uh, you can think of this because the temporal bone is right next to the ear This is where our auditory, uh, signals are going to come from so think hearing and language and sensory in the temporal lobe And lastly the occipital lobe behind the occipital bone This is where all our visual information is going to go So our eyes are up here in the front of the body But there's going to be nerves that run all the way back to this occipital lobe Uh, and it's going to be a rather large lobe. Uh, humans are very visual creatures as with most animals with eyes So we're going to develop, uh, devote a lot of brain real estate to our ability to see, uh, well Moving on then to the second part of the brain It's going to be called the diencephalon And this is going to be located deep in the center of the brain So everything above this is going to be the cerebrum here. Then we have our diencephalon And when we talk about the diencephalon, there's going to be certain structures associated with it For instance the thalamus. This is where all sensory information originally goes So as the information comes up through that spinal cord It's going to find its way into the thalamus And then it's going to be the thalamus's job to direct it to certain parts of the body Depending on what that sensory information is trying to Uh, communicate So say someone touches you on the shoulder, not only is it going to go to the soma sensory cortex It's also going to go to the emotional centers of the brain Uh, for instance, you know, is it your parents touching you on the shoulder to give you Congratulations and you feel good emotion. Is it a stranger grabbing your shoulder and you get scared? So this is how the body determines, you know, when you touch a shoulder, it's the same Sensory fibers are going to fire it no matter what Is happening whether No matter what's happening And it's going to be the brain that determines from all the other cues around you like the social cues The environmental cues and that's how you determine what kind of Sensory information or what kind of response you should develop It's also going to regulate consciousness sleep and alertness So some other kind of more basic functionings Along with the thalamus, then we have the hypothalamus and this is what's going to regulate that autonomic nervous system So the hypothalamus is very important Uh, controlling all the organs of the body So that's going to include things, uh, along with the circadian rhythm So when we wake up and fall asleep as well as your hunger thirst and body temperature Uh, we'll take a closer look at the hypothalamus when we talk about the endocrine system then And just to kind of flesh everything out We also have the pituitary which is going to work very closely with the hypothalamus And it's the pituitary's job to produce hormones So we're going to call the pituitary the master gland again We'll look at that more with the endocrine system And lastly we have the pineal gland that's going to produce melatonin Melatonin is going to be the hormone that helps regulate, uh, your sleep Third part of the brain is going to be the cerebellum It's the second largest part of the brain It's found at the base of the posterior part of the skull So beneath that occipital lobe we have this large cerebellum And frankly, um, we're still learning a lot about the cerebellum in general It's going to coordinate complex muscular movements things like bounce and posture Um, if you mess up your cerebellum You're not going to be able to kind of move easily But there's going to be a whole lot more that goes on there There's a lot of very densely connected neurons within the cerebellum Um, I forget the exact total, but it makes the it competes very closely with the amount of neurons in the rest of the brain So we're still not exactly sure what's going on Totally in the cerebellum for you guys think it has to do with balance and posture So cerebellum I'd like to think like ballerina bellum And then lastly we have the brainstem So the brainstem is going to be continuous with the spinal cord So this is going to act as like the connection between the spinal cord with the rest of the brain So when I asked about the spinal cord what I want you guys to know It's just being able to recognize the different parts that are within it So that's going to include the midbrain Pons and everyone's heard about the medulla emblongata So these are just all parts of this brainstem And what the brainstem's Important function is it's going to be for vital life function. So it's going to help control your heart rate Your breathing sleeping and eating So if you ever had any damage to the brainstem, you're looking at a very life-threatening situation Whereas if you damage the cerebrum or other parts up here, you'll have some fear deficits and certain specific mental functions But you might not Die from them. Whereas if you have any damage to the brainstem, you're looking at very serious issues That's about as much as the book gets into but I do think there are some other areas of the brain that are Rather important There's really no limit to the amount of interesting things in the brain But a couple of them that you'll see Within other readings probably that you might not be introduced to in the textbook One's going to be well in general It's going to be called the limbic system and parts of the limbic system that you see a lot are the hippocampus And what's important about the hippocampus is this is the area of the brain that's responsible for Creating long-term memories. So you're going to have an experience That experience is going to be encoded within your Neurons and sent to the hippocampus where the hippocampus is going to store them away To reference for future use We still now it's important to distinguish the hippocampus creates long-term memories But the memories aren't stored in the hippocampus We actually don't know where long-term memories are stored If we had to guess it's just going to be completely diffuse around the entire brain. It seems So it's still kind of an enigma of where all these memories are stored within the brain Along with the hippocampus in the limbic system is the amygdala And generally when you read about the amygdala, they're probably talking about your fear response But it's going to be a lot more than fear has to more do with emotional arousal. So In this case, just know amygdala has to do with emotions There's going to be certain patients that for various reasons are amygdala no longer functions. Sometimes it can calcify So it'll turn to stone and not work or they'll have it surgically taken out for a specific region and a lot of these patients one of the Kind of classic signs is that they no longer have a fear response. So for instance a lady with her amygdala taken out She was constantly being conned by con men because she didn't have that kind of internal sense that something wasn't right So then just like with every other part of the body, there's going to be connective tissue associated with it So when we talk about the connective tissue of the central nervous system, we're going to term that the meninges So the meninges of the central nervous system is the connective tissue that covers and surrounds The brain and spinal cord and what you need to know about the meninges is there's going to be three distinct layers of it So we're going to start the innermost and work out So the inner layer is called the pia mater And this is going to be very thin and delicate So here we can see our brain and just covering that brain is our pia mater Above the pia mater then we have the arachnoid mater. So this is our middle layer You know arachnoid is going to be what we call or term spider. So it resembles a spider web And within this sub arachnoid space, there's going to be a special fluid that we'll look at next That's going to help protect the brain And then on the outermost layer Another meninges is the dura mater and this is going to be very thick and dense So anytime we talk about connective tissue Generally what's on the outer side of an organ is going to be the thickest And that's because it serves as a protective function. So you want to have the protective layer on the very outside So that fluid I was talking about that helps protect the brain. It's going to be called cerebral spinal fluid So cerebral we're talking about the brain spinal we're talking about the spinal cord So you'll find this csf within the central nervous system And it's going to be a clear fluid within the ventricles that flows around that sub arachnoid space So when we say ventricles, if you ever look at an MRI or any type of like brain scan or an actual brain There's going to be these hollow dark areas in the center And this is going to be where we store the cerebral spinal fluid within these ventricles And there's about 100 to 150 milliliters So fair amount and it's going to surround everything and there's going to be three functions that I want you to know with csf So one it's going to supply nutrients to the central nervous system So because it's so metabolically active, we're going to have to support all that cellular work with some nutrients It's also going to remove the metabolic waste again anytime those cells are doing something. There's going to generate waste So it helps take that away And it's going to act as a shock absorber as well So if you kind of soak the entire brain in this pool of uh liquid when you kind of shake your head back and forth It's not just going to bang against hard bone It's going to slosh within this fluid to help kind of mediate the forces as you kind of whip your head around So it's a good shock absorber If you ever get a spinal tap, this is what they're going to put a needle within the central nervous system in the spinal canal They're going to take a sample of that cerebral spinal fluid out They'll make sure that there's no pathogens or anything within it So moving down from the brain to the spinal cord you can simply think of the spinal cord as just a bundle of nerves extending from the brain stem So it's going to exit the skull if you remember that large hole at the base of the skull It's called the foramen magnum and then the spinal cord is going to go all the way down to about l2 right here So it ends at l2, but then it's going to have a bundle of nerves that extend further down to the limbs So simply the spinal nerve is going to be known as like an information highway So it's what connects the peripheral nervous system to the central nervous system So all those peripheral nerves from the extremities in the trunk We're going to go to uh through their spinal nerves up to the spinal cord into the brain So what you need to know is that there's going to be 31 pairs of spinal nerves that stem from the spinal cord So you have 31 from starting from c1 all the way down to the bundle near the sacrum And when I talk about that bundle at the base of the spinal cord, this is going to be called the cauda equina So equina this is going to translate to horse tail So the bundle of nerves that kind of fan out is going to look like a horses tail if you look at them in isolation And that's going to be from l2 to l5 Zooming in at the spinal cord, then you'll recognize this again from the muscular system We can kind of divide How the peripheral nervous system enters and exits the spinal cord So when we look at the dorsal aspect of the spinal cord This is going to be responsible for the sensory input So there's spindle cells, golgi tendon organs that we looked at they're going to go through the dorsal part of the spinal cord And so we call this the sensory part and what you need to know is sometimes They're going to use the term afferent or an afferent neuron to signify that it's sensory So afferent means that it's going to somewhere In this case it's going from the peripheral nervous system to the central nervous system So the opposite of an afferent neuron then is going to be an efferent neuron Why they had to pick such similar sounding words Is just too bad, but when we talk about efferent neurons, we're talking about those motor neurons So these are going to be exiting the ventral or the anterior aspect of the nervous system And leaving to go out to the skeletal muscles So efferent means that you're going away from something in this case We're going away from the central nervous system out to the peripheral nervous system So then just to help again, this is going to be the front of the spinal cord here This is the dorsal aspect of the spinal cord so ventral root dorsal root So the best way to kind of remember which one's sensory, which one's motor is to think of the word same So s-a-m-e, s in the a stand for sensory afferent Or the second half of the word me, me stands for motor and efferent So it'll be easy to mix this up because the emblems might instead of saying the sensory nerve or the sensory neuron Those might say this afferent neuron and they're just going to want you to know that they're talking about sensory and not motor A couple other terms that you'll see This word ganglion, you don't see this too much. I'd be surprised if you see this on any Emplex question, but ganglion is just going to mean a cluster of cells So all these nerves that run out from the central nervous system to the peripheral nervous system They're going to be mostly axon. So the nerve at the tip of your toe It's going to be a long axon that goes all the way up to basically the spinal cord But like every cell we need a cell body. So all the cell bodies to these neurons are going to exist In this dorsal root ganglion and that just means a cluster of cell bodies For all those axons that go into the extremity from this nerve root So all the cell bodies are going to exist in this certain area right before the spinal cord So for the sensory ones, we call this the drg or the dorsal root ganglion They'll also be a ventral root ganglion somewhere Uh ramai, we saw ramai or ramus when we looked at the parts of the bones or the pelvis in particular But a ramus again, you're thinking of a branch of a tree or branching So ramai in the nervous system is branches of nerve roots. So here we have our Ventral nerve root and different parts of the ventral that stick out then are going to be called different ramai Don't worry about the specific names. It's just parts of the nerve root that go somewhere else And then lastly we have what we call a nerve plexus And a nerve plexus is going to be a network of closely intersecting spinal nerves So in some areas of the body, we're going to have to kind of smush some nerves close together To get them to go all to the same area. So you'll see this, uh, there's four plexus that you uh, It'll be good to know about So the first one is a cervical plexus and that's going to be from c1 to c5 Next further down from c6 to t1. We had the brachial plexus Brachial plexus, we'll talk about more when we do medical massage This is going to be a large group of nerves. Just let me zoom in here for a second Here we can see this large group of nerves and the brachial plexus Still figuring this thing out So these nerves that are all going to be what innovate through the shoulder down to the arm So they innovate the entire arm and what can happen sometimes is they'll pass underneath certain muscles or certain other structures of the anatomy And if they become impinged or irritated, uh, you'll end up with a certain neurological symptoms or neuropathy Uh, in the case you might get numbness in the hands or pain the shoulder thoracic region and that's going to be called Part of what we call thoracic outlet syndrome and there's going to be certain massage techniques that can help treat somebody that's suffering from Thoracic outlet looking down then we have our lumbar plexus So that's going to be l1 to l5 and the sacral plexus a lot of times you might just see this called the lumbaral sacral plexus But overall there's four total as you know So again the four plexus are going to be cervical thoracic lumbar and sacral and all it means is a bunch of nerves close together Here, uh, we're going to be talking about our dermatomes and myotomes and we've already introduced dermatomes when we talked about shingles or certain touch receptors And when we say dermatome, this is going to be the specific area of the body that those sensory spinal nerves innovate so like we said um Each of those 31 pairs of spinal roots or spinal nerves are going to uh Be responsible for a specific area of the body. So sciatica is a common Pathology that we're going to see and sciatica is generally going to be caused by irritation Of those lower lumbar roots So say if you have a herniated disc at l5 s1 the l5 nerve root is going to be irritated and there's going to be a rather general region that that l5 nerve Uh, send signals to so anywhere where you see this dark yellow. So l5 is going to be Sensing signals from the anterior part of the shin as well as the outside portion and the posterior part of the thigh This isn't really a great picture to show you the all the errors that l5 does but the idea is that Basically, if you had tingling in the hands in the arm, you know, it wouldn't be caused by A herniated disc in the low back those nerve roots simply don't communicate with that part of the body So it helps you kind of narrow down where the issue may be So it can be used as a diagnostic criteria for our doctors looking at these conditions And then with uh, along with dermatomes, there's also a myotome And this is going to be groups of skeletal muscles supplied by a specific motor Neuron or nerve You generally don't see a lot about myotomes Uh, I rarely read anything about dermatomes is going to be the one that you're going to get a question about Because when we talk about pain or chronic pain, uh, if it's caused by a nerve issue It's generally going to be found within a specific dermatome and that's going to be Helpful to know about you wouldn't have to know this entire map But if you were able to reference this depending on what your client is telling you Could serve you to help you better understand What what possibly be going on and again, you wouldn't diagnose them saying oh, you have a herniated disc here because of that We don't know that information, but uh bearing any Limited information you could kind of keep that in the back of your mind as far as how you would Go about with treatment protocols Next we have what we call cranial nerves and what's special about cranial nerves is that they emerge directly from the brain And what that means is that they're going to bypass the entire spinal cord So there's going to be 12 pairs in total Uh, and they're because they come out from the brain It means they're going to be responsible for areas around the brain And that's going to include the head face and one nerve in particular goes all the way down through the chest And they can be either sensory motor or both Um, I don't use the term but if it does both sensory and motor, they're just going to be simply called a mixed nerve I've seen that question on abnp. So a mixed nerve just means that there's both a sensory and a motor neuron within it I'm not real big on carrying A lot about cranial nerves It's kind of like an initiation into anatomy 101 that you memorize all the cranial nerves and what they do I'm not really sure that uh all the effort that goes into memorizing these cranial nerves is going to pay off At most you'll probably get one question on amblex about them if any so I'll introduce them. I'll ask a couple questions about the more important ones It's going to be important that you know that there's 12 of them and that you can at least Name all 12 and uh, which correct number that they are whether or not, you know, they're sensory or what they're responsible for That's going to be extra information where if you basically know everything else about anatomy And you want to still study more uh, go ahead and study more of the cranial nerves But i'm not going to really hammer down on making sure you guys know every piece of information about them And a lot of times you can use their name as kind of a clue of what they're responsible for So for instance cranial nerve number one is the olfactory nerve And if you don't already know we're going to learn soon that olfaction is just a fancy term for smell So the olfactory nerve is a sensory nerve that has to do with smell Again, you know it's sensory because of those five senses we talk about smells going to be one of them An optic nerve has to do with uh vision again You can pretty much guess when you see the term the prefix optic you're thinking eye and vision So cranial nerve number three is ocular motor and then ocular again You're thinking eye and motors right in the term. So, you know, this is a motor neuron So this is going to help uh, the visual system help I believe the eyes move even I don't know exactly what they do Trochlear again Cranial nerve number four is trochlear and it's a motor neuron that has to do motor nerve has to do with eyes again Because the eyes are so important. We're going to have multiple cranial nerves that are responsible for different functions cranial nerve number five is the trigeminal This is part of a sensory function within the facial area So you different parts of your face the feeling of it as well. It has some motor function for chewing muscles I might ask you about the trigeminal just because there is When you have chronic certain chronic Neuropathy of the face a lot of times the trigeminal nerve is part of it So if you get shingles sometimes it affects the trigeminal nerve Or I believe there's suicide headaches, which are really bad headaches that have to do with irritation of the trigeminal nerve as well So there's going to be some pain conditions that references cranial nerve number five Cranial nerve number six is the abdicens again eyes are important. So there's another motor nerve for that Cranial nerve number seven is facial. So again, this has to do with taste and some facial muscles the motor Cranial nerve number seven when we talk about Bell's palsy This is going to be an issue with cranial nerve number seven and people with Bell's palsy They're going to have a drooping of one side that that nerve affects So that's why the facial muscles are affected with Bell's palsy Cranial nerve number eight is the vestibulo vestibulo cochlear cranial nerve has to do with balance and hearing So the cochlear we're going to learn has to is within the ear And that's where we have our sense of balance as well as our ability here Cranial nerve number nine is the glasso farangial If you remember way back to medical prefixes anytime you see glasso You're thinking tongue. So in this case it has to do with taste and swallowing Farangial is the back of the throat Cranial nerve number 10 then is the vegas nerve and if you're ever going to see anything as massage there It's generally it's going to be about the vegas nerve Just because it has so many different functions because it affects so many different organs So it's both sensory and motor, but it can affect your ability to sweat your heart rate As well as your speech and breathing And then looking at the last two cranial nerves, we have cranial nerve number 11 the accessory nerve And this is going to innervate some of the upper back muscles like the trapezius And with cranial nerve number 12 being the hypoglossal again glasso you're thinking tongue So it has to do with your ability to move your tongue So as with anything in anatomy that you have to spend a lot of time memorizing Someone's come up with a mnemonic to kind of help you remember the order in which the cranial nerves are named So the mnemonic To touch and feel very groovy virgins at home and as with any good mnemonic It's going to be a little bit perverted because one thing about our brains is It's much better remembering things that are kind of Emotionally arousing or just emotionally memorable so hence the kind of Weird mnemonics that I kind of introduced to you guys But the idea is if you can remember this simple sentence You can remember the order of the cranial nerve. So if you were getting a question like What's this fifth cranial nerve has to do with The face you can see one two three four five You know the fifth one has to do It's going to at least begin with a t and with a multiple choice question There's only two cranial nerves that begin with t So now you have a 50 50 chance instead of just a complete random guess So that's why it's important to remember some kind of mnemonics Just so you can remember the first letters of each of those cranial nerves Moving on to reflexes then we already talked about reflexes when we talked about those proprioceptors But again a reflex is going to be an involuntary and predictable protective response to a stimuli So that can either be a muscular contraction like we saw or even a glandular secretion So there's going to be two kind of major Types of reflexes the first one's going to be a cranial or visceral reflex And because it's cranial it's going to be initiated by the brain. So this is going to be things like blinking Uh forming tears salivating or gagging. These are all cranial reflexes So here we have a nice little picture of a nasal pharyngeal swab Kind of made famous as this is the current coronavirus test So so far my wife's got two of these and every time I've heard someone who's gotten this A swab test is your eyes immediately start to water So that'd be an example of a cranial nerve reflex But it's kind of interesting to see this is just how far back Those nasal cavities go And then the one we already looked at it was the spinal or the somatic reflex And this is named after because it's going to be initiated at the spinal level Again, you have that sensory nerve going through Uh to the spinal cord and then it's going to send a motor signal out to the muscle to cause a Reflex so we looked at the quadriceps of the patella reflex But there's going to be multiple reflexes at all different parts of the body So doctors will do different ones at different joints It's just the knee is the easiest one to do I'm guessing for the most Obvious and if there was something wrong with either of these reflexes It would kind of give you a clue that something's going wrong At that level So we're going to briefly talk about the senses. Uh, this is going to be very brief overview We're not going to get too much into it just the basics and that's going to include the different types of sensory receptors So this is going to be straightforward multiple choice questions things like a chemo receptors are going to detect chemicals And we'll just go down and look at each of these in particular photo receptors Photo you're thinking light the thing receptors in the eye Thermo we said are going to detect temperatures nociceptors detect noxious stimuli a lot of sources and I wouldn't be surprised if emplex makes this kind of Mistake is they'll say nociceptors detect pain when we talk about pain later in the course It's important to know that all the sensory information from your nociceptors It isn't pain until the brain says it's pain. So it doesn't matter What's going on in the periphery the brain is going to be the ultimate determiner If something's painful or not So like the classic example is if you just scored a touchdown The Super Bowl and your whole team jumps on top of you and celebrating you're going to be firing these nociceptors off like crazy but You're not in a dangerous situation Your body doesn't care about any of that So it's not going to send a signal saying that you're in extreme pain Because it's thrilled that it just won't you just won the Super Bowl So again, it detects noxious stimuli not pain stimuli and when we say noxious, we're just talking about excessive temperature or potential tissue damage And then lastly is the mechanoreceptors, which we just saw in the skin system. So there's touch receptors that sends pressure and vibration So I'm looking very closely the chemoreceptors you're going to find on your tongue. So your taste buds As well as within the nose So chemoreceptors in your nose are going to be what sense smell and again that sense of smell We're going to call the olfaction So anytime you see the word olfactory like olfactory nerves or a factory tract We're talking about nerves associated with your sense of smell Here we have hearing. So how hearing works again Sound is just going to be vibrational waves that are transmitted through the air or some sort of medium So as those sound waves enter through our eardrum here We're going to be kind of channeled into the ear canal Where they're going to cause this eardrum known as the tympanic membrane to vibrate And it's this vibration of the eardrum that's going to cause these three little muscles here called ossicles The vibrations are going to be transmitted and amplified through these three small bones And this uh last bone here is going to kind of hit on This uh cochlea that's filled with a bunch of fluid So as you pound on this cochlea, you're going to cause the fluid in this co- As you pound on this cochlea you're going to cause the fluid in here To also vibrate and it's going to be the vibration within that fluid That stimulates these special hair cells within the Semi-circular canal and that's going to be what stimulates the auditory nerves to transmit hearing So it's just a propagation and kind of amplification of sound waves Until they finally get to the sensitive nerves deeper into the ear As far as what you find need to know Cochlea, I've seen questions Anytime you see COVID know that we're talking about hearing or the ear So we just saw that with the cranial nerves, but cochlea is going to mean snail shape So you can see this Kind of little organ here has that snail shape or snail shell shape figure When we talk about vision, um, I'm not going to ask a whole lot of questions on it But some more common kind of anatomical terms that you'll see is the cornea is going to be this outer lens So it's the outermost part of the eyeball. So when you hear people scratch the cornea That's because it's the part that's exposed to the outside environment Going inward then we have the iris is going to be a muscle and that's going to control how dilated or constricted your pupil is So as your pupil becomes more constricted, it's going to cause it to lessen up and when we say pupil, this is like the hole Within the eyeball that allows light to pass through it So the larger your pupil is the more light beams can enter into the eyeball But before it gets to the back of the eyeball, you again have this second lens here That's going to help focus light onto the back of the eyeball And the back of the eyeball is going to be called the retina And it's within the retina on the back of the eyeball where you'll find those photosensitive receptors So those photoreceptors are going to be very numerous on this back part of the eyeball called the retina And then once those photo cells on the retina are stimulated They're going to send a signal through this optic nerve back to the occipal lobe world process the visual stimuli So what's interesting if you kind of take a look at this picture here You'll notice this optic nerve because of its In the back of the eyeball, there's not going to be any photoreceptors in this particular area So each eyeball has a blind spot to it. So when we next meet in class I can give you a little experiment where you can notice your blind spot In each of your eyes, so you have to close one eyeball and your blind spot will become Noticeable with certain experiments And again here the way it all works the light photons are going to pass through the eyeball They're going to pass through the two lenses and because those lenses are curved in a specific shape They're going to cause those light rays to converge and to a pinpoint area on the back of the retina So when you get the light convergence at just the right spot, you'll have very clear vision If your lens or the front of your eyeball or your eyeball shapes oddly and it causes This reflection of light rays to not quite be perfect. That's when you're going to need certain glasses to help Bend those light rays So what you should know as far as the photoreceptors, there's going to be two major types There's going to be rods and cones So rods are going to be more on the peripheral part of the visual system. So they're good at detecting low light So seeing things at nighttime And again, they're more prominent in the peripheral so If you ever watch some of those survival shows If you're kind of stuck in the woods and low light setting What you can do is a kind of look out the sides of your eyes and you'll get a more clear picture of what to see Whereas cones are going to be more in the center of your visual field And they're going to detect bright lights and colors. So cones are responsible for color vision rods are for black and white vision So when you have certain types of color blindness There's going to be some cones that don't function properly And there's multiple types of color blindness and again, I can give you guys a test to see If you're a color blind or not And then we're going to briefly look at the kind of anatomy of the nerves and the neurons themselves I'm not going to spend a lot of time looking at the particulars of a nerve But what's important to realize is when we've talked about Neurons so far we've talked about a single cell And like axons and the dendrites and what they do but just like muscles These nerves are going to be put together and bundled together in a large compact Structure called this is what we call a nerve And it's going to be named directly or exactly the same as we name Muscle cells instead of calling them mysilm. We're just going to call it Neurium So if we start small we can see an individual nerve cells in neuron and it's surrounded by connective tissue called endonurium We're going to kind of group all those individual neurons together into a fascicle So that's the same as a muscle and it's going to be surrounded by connective tissue called perinurium And then all these fascicles are again grouped together And bundled into a fiber that we just call a nerve And this entire nerve is going to be surrounded by connective tissue called the epinurium So I understand you guys already know this about how muscles are named So as long as you remember it's neurium instead of mysilm. It's basically the exact same So i'm not going to retest you guys on that But the important thing is there's going to be many many neurons in each nerve So a large nerve the large nerve of the body is a sciatic nerve There's going to be many many many many many neurons within that sciatic nerve And they're going to branch out into different areas and innovate different things And this is how you can have both sensory and motor neurons within the same nerve Because there's many different tracks Here, you don't need to know any of these cells in particular All I want you to know is that neurons are going to function in isolation They're going to have a lot of support cells So cells that support neurons are called neuroglia Glia is going to I think Latin for glue And they originally thought these were just cells that kind of held the neurons together But we're really kind of discovering now that neuroglia have a lot of specialized functions that Can contribute to a lot of different things So neuroglia are kind of much more important than what they originally thought were just kind of like connected tissue And there's going to be different types found in different areas of nervous system M. Bleck specifically says you don't need to know anything about neuroglia So don't worry about any of this information. That's kind of just extra stuff When we talk about the anatomy of a neuron, we've already talked about the very basics and that includes the dendrites and axons So for dendrites, you should be thinking this is the part of the neuron that receives information So here we have a bunch of dendrites on our neuron and there's going to be connections to each of these dendrites From other cells. So they're receiving information from other neurons And then if you stimulate the cell it's going to send a signal down the axon So it's this axon that transmits any information. So dendrites receive axons transmit And then we'll look at the actual potential more again and Bleck says you don't need to know how actual potentials work I'll still explain it in another video But I won't ask about it on the test. It'll probably just be extra credit if I do But at the very start of the axon there's what we call the axon hillock And this is where an actual potential either Decides to begin or doesn't decide to begin So basically if you stimulate the axon hillock the entire axon will fire an actual potential So you can think of the hillock as kind of like the first domino in a string of dominoes If you knock down that axon hillock the the rest of the neuron is going to follow along and transmit the actual potential too And to help the speed of the actual potential There's going to be that fatty substance that covers the axon and this is called a myelin sheet And the whole point of myelin sheet is to speed up the conductance of that electrical signal And we'll get in the next video look at how myelin accomplishes this But the more myelin the faster it can go if there's no myelin The signal is going to be transmitted much more slowly And then you'll notice that the myelin isn't one Complete covering there's going to be sections without any myelin interspace between the Down the entire axon and this is going to help Kind of restrengthen the signal if it was just one sheet of myelin the signal would come become weaker and dissipate In this case, we can kind of stimulate those ion channels and kind of restrengthen the actual potential as it goes along So these gaps in myelin sheet are called nodes around da And as far as the different types of neurons, we also saw this in the muscular system Basically three major types. We have excitatory neurons where they're going to basically Signal from excitatory neurons going to tell the neuron it connects to to also Transmit actual potential Whereas an inhibitory neuron is going to tell the neuron It's sending signal to to not send the signal So i'll kind of give you guys a diagram in the next lecture of how these excitatory inhibitory neurons Kind of create what we call a network or a neural network of Signals and then we also have inner neurons and these are going to be much smaller neurons and their job is to help modulate so While it can be like an all or nothing with the actual potential We can make these cells more or less likely to fire and that's going to be the job of these inner neurons And when we look at these neural networks, we already saw these terms when two neurons connect We're going to call this a synapse. So synapse is simply the connection of two neurons And we can uh have different names for the two neurons that connect So the neuron that's sending the signal is called the pre synaptic The one before the synapse And the one that's receiving the signal is the post synaptic. So it's receiving the impulse You can see here that at the end of both of these neurons We kind of have like a growing out of the synaptic bulb or the the tip of the neurons So this outgrowth, uh, that kind of makes it a bulb shape. It's simply the synaptic bulb. So it's the end of a neuron And then as we showed there's a small space. So there are some neurons that they have direct connections So there's no synaptic cleft But the majority of neurons there's going to be this tiny space that allows for the neurotransmitters to float around And this allows us to help modulate the strength of the signal or weaken the strength of the signal So that again, it's called the synaptic cleft or the synaptic gap And we already saw the neurotransmitters is going to be that chemical messenger that's released by the neuron So the pre synaptic cell releases the neurotransmitter the post synaptic cell has receptors That are going to be sensitive to that neurotransmitter Then very briefly looking at what neurotransmitters are Again, they're going to be stored in these vesicles at the tips of the pre synaptic bulb And then the atrium potential what we saw is going to cause these to dock to the Cell membrane and be released into the synapse So what I want you to know about neurotransmitters the book has a whole list of the different ones and what they Are responsible for Again, Emplex says you don't need to know all that specific and it's not important for our case so much But what you should know is there's two major Ones that are involved in excitation and inhibitory function So in general glutamate is the most excitatory neurotransmitter So if we want to stimulate another neuron Glutamate is by far the most common neurotransmitter that we'll use Whereas if we want to inhibit another neuron that neuron is going to release GABA GABA is just A shortening of a much more complicated word The GABA is going to be inhibitory neuron Again, the book doesn't even have glutamate for some reason. I don't know how they've left that one out But these are the only two I really want you to know The more common ones that you hear about a lot are going to be like dopamine serotonin acetylcholine These are common, but they're in much less supply than either glutamate or GABA So you can think of these as kind of like the monetary neurotransmitters And the reason I don't expect you guys to really know about what they do Is the the function of a neurotransmitter doesn't really have to do with the neurotransmitter itself It has to do with The receptor on the neuron that it's receiving it so dopamine can be either excitatory or inhibitory depending on the neuron That we're talking about And that's everything. So the next class we're going to go over certain pathologies I don't like to get into neuro pathology too much because a lot of the ones we don't even really understand Exactly what's going on. So I'll give you a couple choice examples And I'll show you like a lot of times the pathology has to do with There's something wrong within the pathway So one of the neurons isn't working right and the signal is being messed up. So There's not a lot to talk about