hey class welcome to the nervous system lecture in this portion we will talk a bit about the background of the nervous system but mostly its how its the nervous system organized that we'll discuss so jump right in the nervous system it actually works together with the endocrine system to control and adjust the activity of all the other systems and the nervous system does this relatively quickly by firing these action potentials these electrochemical signals throughout the body this happened fairly immediately the endocrine system takes slower to respond we've talked about the different ways that hormones are released for example by monitoring fluids or through a neural stimulation but a lot of it is through hormonal control of hormone release so it's this cascading effect so it takes time to release the hormone that's going to cause the release of the other hormone that then has to circulate in the blood to reach the organ with the receptors and a very different way of controlling your body systems but they do work together so for organizing the nervous system I have this drawing that we're gonna walk through pretty slowly because it is crucial to understanding everything that we do for the whole rest of the unit so if we're gonna draw the nervous system organization I'm just taking screenshots from an old drawing but we would start by thinking about the brain and spinal cord most people know the nervous system contains these two objects and they do make up the entirety of the central nervous system they're responsible for integrating and processing information so what I mean by that is when information arrives let's say from your eye on the photoreceptors on the back of your retina that an information comes in but it needs to be processed meaning you might know that the information crosses to the other side of your brain of your head and it's upside down and the brain needs to kind of make sense of that flip it around but also it will integrate that information with other parts of your brain so usually I pick someone in the class and I say okay so here's so-and-so and I can see what I see a kind of a dark blob and then like these shapes and kind of round things here and a triangle here and you know that that's what the photoreceptors tell my brain but that's not gonna do me any good I want to know like who is this person based on these features do I know them do I like them do I need to tell them something oh I remember that they didn't take the test you know am I am I scared of them are they acting socially normal like their facial expression does it show interest or boredom or frustration so all of that relies on this integration piece of the central nervous system that's kind of where I think all the interesting stuff is in integration everything else that we're gonna do on this drawing is the peripheral nervous system so yeah get to know get ready to learn a lot about the peripheral nervous system see these lines here they're kind of indicating okay everything down here will draws the P and s starting with the fact that if the brain and spinal cord are going to integrate and process information information must arrive at the CNS so the nerves that carry sensory information that arrives at the CNS are a afferent or afferent nerves information arriving starts with a often maybe not always often the the CNS will decide have some response based on this sensation that's arriving so when there's an effect that happens these efferent or efferent nerves send out motor commands let's do a real quick obvious example if the sensation that's arriving on these a forint arriving nerves is that you've just touched a hot stove the efferent nerves will send a command to your skeletal muscle to pull your hand back before it gets severely burn so sensations arrived motor commands exits of course there are many different types of sensations for example special senses special senses is those are anything where there's a unique like instrument or organ to capture this sensory information meaning the eye is the only thing that captures sight after is visual information only the tongue does taste only the nose does smell only the ear does hearing as well as in the inner ear is balanced so these all have a special mechanism or organ that captures the sensation so those are all special senses so all that information arrives at the CNS through these a foreign nerves what about touch though what about touching the hot stove and pulling away all right here's my little drawing of touch that is a somatic sense you may recall soma means any one any one means body like the soma is going to be the cell body of the neuron so soma means body so these somatic senses come more like from the body not these special parts of the body like the eye so touch this lightning bolt into a sad face is pain there's temperature and even here with these arrows pointing to a muscle and to the elbow joint here we're talking about like how much are your muscle is currently contracted or what position are your joints in that information actually arrives at your central nervous system constantly and in fact if you were to I don't know be floating in space or something with your eyes closed you would still know if your your arms your you had flexed your elbow or if your elbows were fully extended you could tell that because that information goes to your brain so what's you did all these special organs we did quote unquote the rest of the body but we didn't get into any of those internal organs heart the lungs uterus and penis for reproduction here's a stomach with some intestines so these are all visceral senses because your viscera are your organs you might recall that from the visceral layer of the serous membrane from unit one you might know about it from Jurassic Park first movie when they talk about raptors eviscerating someone so removal of the organs is the serration so anytime you see viscera or a visceral response is like something from deep within you that means organs so that's all the sensory information that will arrive through these nerves into the CNS now let's talk more about what might your brain and spinal cord decide to do with that information it might decide to have some somatic response now you see we're reusing this word somatic and in fact we can make a whole new chart that group this stuff a little bit differently kind of smooshed these two somatic areas together but let's just think about this as a motor response in which muscles are controlled skeletal muscle specifically so this would be the hand pulling off the stove you could say this could even be like okay your body temperature is starting to drop so you just use your skeletal muscle to go get a sweater this doesn't have to be all reflex actions but what about the other types of muscle well final chapter here is that the CNS can also have some kind of motor or efferent response not just through skeletal muscle but through two other divisions which are autonomically controlled when you see Otto that means self automatic is like a self shifting car right automatic whatever so this is basically doesn't mean automatic but make sure you say autonomic spell autonomic but these are these automatic responses it's not voluntarily controlled it's all involuntary and you have two divisions sympathetic and parasympathetic sympathetic you've probably heard of before because you've likely heard of the fight-or-flight response we'll talk more about this later we have a whole chapter on the autonomic nervous system but for now we'll just simplify it let's say you are in the fight or flight of your life right like people always say like getting chased by a saber-toothed tiger - think about how this is evolved so you're getting chased by the saber-toothed tiger what kind of things do you not want going on at that moment you don't want like an erection or sperm being made or planning your next ovulation you don't want to be worried about digestion or the rate of blood filtration that's happening in your kidneys so this kind of stuff you're gonna shut down but you'll increase things like respiration rate so you start to breathe faster you need more oxygen because oxygen helps make the skeletal muscle do its thing you need to get a little muscle to either fight or run away but if you have more oxygen you also have to get it to your cells so you'll increase your heart rate your heart rate will go up your heart will beat faster to help move this oxygenated blood to where it needs to get your basal metabolic rate will in you need these cells to take this oxygen that's being moved through your blood to these organs and like grab the oxygen out of there use it to convert glucose into ATP the ATP will power your skeletal muscle it's all kind of the same goal here and there's other stuff that needs to happen like release sugar into the bloodstream if you want to make ATP mostly we've talked about getting oxygen but you also need that sugar so the liver will release sugar into the bloodstream so those are mostly related everything we talked about there but also your pupils will dilate you want to be able to maybe see a tiny bit better in that moment that you're fighting or fleeing you will sweat your erector pili muscles will stand up blood will be redirected for more superficial areas like in your skin - the organs that need it mostly like heart and diaphragm and your skeletal muscle so we can go on and on and we will during a and s chapter the autonomic nervous system but for now you know just kind of pick a few of these that make sense to you and start to use those to understand what the sympathetic portion of the autonomic messages are and then last there is a parasympathetic portion of the nervous system these are these efferent responses that are doing usually the opposite of everything we just said so who's going to tell your heart to slow back down your respiration rate to decrease your BMR to go back to normal who's gonna tell your sweat glands to stop making so much sweat your erector pili to chill out and your pupils to go back to normal all that stuff is going to be signaled through the parasympathetic nervous system sometimes called the rest and digest branch or feed and breed all just like cutesy little sayings to try to help remember the major functions of this branch of the nervous system the one last thing want to say is that all these portions or divisions or subdivisions or segments or categories none of those words really matter what matters is things like autonomic somatic special senses visceral senses whether you want to say that visceral senses are a branch of the afferent division or they're a section or a chunk or a category or a subdivision doesn't matter yeah so you might hear me use those interchangeably at times but you know don't worry about using that specific terminology just know like yeah these are all related to each other and keep in mind that often the simplest way to do this is just say all of this is the sympathetic nervous system this is the parasympathetic nervous system this is the autonomic nervous system the somatic nervous system is includes this sensory system includes all of this so there's lots of different words out there to kind of capture your meaning and as we practice this it will become more clear so next we'll jump into the neural tissue and start to look at neurons and glial cells see you then