hi I am Orel Enriquez and this presentation contains our discussion on the nervous system this slide shows us the two divisions of the nervous system CNS or the central nervous system and pns or the peripheral nervous system central consists of the brain and spinal cord peripheral consists of Al the nerves that extend outwards or distal to these spinal cords listed here are the functions of the nervous system first up is sensory input whether this would be physical input such as the cold or the heat or being punched in the face non-physical input such as hearing sounds or being presented with new information so next integrating or processing that information the brain would now decide what to do do with that information next is controlling the muscles and glands so this is applicable both for voluntary and involuntary muscles bra responsible is that voluntary muscles but for involuntary muscles as necessary or as needed next is maintaining homeostasis or balance so imbalance hormonal imbalance the brain would communicate with the endocrine system um imbalance with body temperature the brain would communicate with the integumentary muscular and cardiovascular system electrolyte imbalance um the brain will communicate with the kidneys so those are just a few examples of how the CN s would maintain homeostasis last one is establishing um and maintaining mental activity so part where our nervous system makes us nervous all right so um feeling different emotions is a product of mental activity so contrary to the popular saying that emotions come from the heart um no not really to simplify emotions are our response to stimuli that has been presented to us and that response is because a mental activity or processing of information happened in our brain the central nervous system is comprised of the brain and spinal cord and the peripheral nervous system includes all other um nerve tissues extending out of the CNS now what is the sensory division this conducts action potentials from sensory receptors in the CNS basically div which to receive sensory input next we have the motor division so this conducts Action potentials to organs like muscles and glands basically organs if needed so as the name implies no motor this is responsible for movement but wait there's more um next is the somatic nervous system this transmit Action potentials from the central nervous system to the skeletal muscles so um must specific specific specifically n system skeletal muscles sotic division cardiac and smooth muscles so who's the boss of the smooth and cardiac muscles it's the autonomic nervous system next is the anic nervous system when we say anic this is anything that has something to do with only the digestive tract this slide shows us kind of like an organizational chart for our nervous system showing the different divisions that we just talked about let's now talk about the cells of our nervous system neurons receive stimuli conduct Action potentials and send signals to the other neurons or the effector organs leader right so group work next are gal cells so gal cells these are the supportive cells present at both the Central and peripheral nervous system they don't conduct Action potentials they can't do the things that neurons would do but being the supportive PR that they are um they can enhance no they can enhance neuron function and um so gal cells are kind of like your supportive besy that um encourages you to do things let's now further discuss neurons specifically its parts so the cell body is kind of like the main component of neurons because this is where we would find the nucleus the dendrite is where the cytoplasm is and shape dendrites so they're not exactly round like the cytoplasm of most cells that we've talked about in the so cytoplasmic extensions that are capable of receiving and transmitting chemical signals and other information soes communicate all right so dendrites can receive info from other neurons and transmit that information to the cell body process neuron third component is the axon okay so the axon is a long tail like structure extending away from the cell body so send sensory signals central nervous system and also to send motor signals C Andor or Ora in this situation this illustration shows us the basic structure of AAL neuron so here's the cell body and then these short Branch like cytoplasmic extensions are the dendrit and then this long segment right here is the axon neurons also have different structural types multipolar neurons have many dendrites but just one Aon so Pho on the previous slide that's an example of a multipolar neuron so or majority neurons multipolar next bipolar neurons um as the name implies only have two processes or two extensions one dendrite and one axon so bipolar neurons can be found in some sensory organs like the eyes and nasal cavity there's also what are called pseudo unipolar neurons so they only have one structure extending away from the cell body so Isa process or extension but this one extension actually branches no actually branches into two so Direction branches um one extends to the central nervous system while the other extends to the peripheral this slide shows us illustrations on the three types of neurons so multipolar neurons are the most common extensions axon bipolar neurons um have only one dendrite and one axon and then the pseudo polar or pseudo holar neurons look like they only have one axon but actually this branches is into tube let's now talk about gal cells again they're the supporting cells of the Central and peripheral nervous system there are actually many different types of this first of are Astros sites and for the most part asites CNS all right so they can either stimulate or inhibit so either encourage the signaling activity of nearby neurons from the blood brain barrier the blood brain barrier is a highly selective semi-permeable border of endothelial tissues that control substances that could pass through um or from the blood circulation nervous system ases either stimulate or inhibit signal blood brain barrier the next supportive cell or epinal cells so they line the cavities or the hollow spaces of the brain that contains cerebrospinal fluid so cellu cerebrospinal fluid next are micral cells so micral cells work as if they're part of the immune system micral cells could get rid of bacteria and cell debris in um in case damage cells central nervous system next are oligo dender sites so they provide myeline to the axons of neurons in the CN s myeline is uh made up of proteins and fatty substances that forms a sheath or covering around the axons next are Schwan cells Swan cells also provide myeline but these ones um s peripheral nervous system word so again in comparison to oligodendrocytes no they also provide myeline oligodendrocytes CNS cells pns so same function different location this slide shows us an illustration on what those cells we just talked about would probably look like let's now talk about the myeline sheath these are structures that wrap around the axons of neurons if a neuron has an axon wrapped in myene sheet myelinated this implies the existence of neurons that are not myelinated okay neuronsin axon in the central nervous systemes serve to form myeline sheets but at the peripheral nervous system it's the Schwan cells that work to create the myeline sheet there may be spaces or gaps in the myene sheet and these are called the nodes of ranar so ions can diffuse in and out of the neurons through these nodes of ran aside from just being a physical insulation or covering sheath is to increase the speed and efficiency of action potentials passing through a a now what happens if neurons supposedly myelinated problems there's a disease of the myeline sheet that is known as multiple sclerosis and this leads to the loss of muscle function see the movement of muscles are also controlled by the action potentials being generated by neurons capability to control the function of muscles let's now talk about neurons that are naturally unmated neurons shape um this could usually be found in indentations of oligodendrocytes CNS orwan cells pns neuron observe we'll better understand this if we take a look at the illustration on the next slide here's a side by-side illustration of a myelinated axon in comparison to unmyelinated axons notice that if an axon is myelinated M and it's very well wrapped up in that myeline sheet in comparison to unmyelinated axant um there are multiples of them embedded in just one swan cell and they're not even fully covered as you can see in the exposed areas right here so those are the differences between a myelinated axon compared to an unmyelinated axon now the color of the nervous tissue depends on the amount of myelinated neurons in that specific area gray matter is composed of neurons where there's little amounts of melanin white matter is composed of bundles of axons with myeline sheets so gray matter less myeline white matter more myelin let's now talk about how nerve cells communicate here we use the term excitable um nerve cells that are previously resting have the capability to respond or react to stimulate so these reactions or changes becomes a way for nerve cells to commun communicate with one another for humans this is comparable to body language so if a person moves closer to you when you're talking it means that they're comfortable or they're paying attention to you if a person um slaps you in the face because of what you said it probably means that they're mad at you so nerve cells their responses or changes because of a stimuli is how they communicate with other cells now how fast are action potentials conducted from one cell to another as it says here um there is a great variation based on the diameter of the axon fibers so for those of you who already forgot their um geometry diameter it's the length of a line through the center that touches two points on the edge of the circle as you can see right here in this popup illustration so to simplify mediumsized axons conduct action potentials um much slower no 15 m per second larger axons have a higher conduction velocity or signals at 120 m/ second so medium diameter axons slower large diameter axons faster let's now talk about synapses or neuron neuronal synapses these are spaces where an axon of a neuron would interact with another neuron so axon would be called the preoptic terminal memane that would be called the synaptic terminal next term that we need to know are neurotransmitters so any chemical being released by one neuron through its axon at the preoptic terminal potic terminal neuron is known as a neurotransmitter again explanation neurotransmitters or chemicals released by neurons that could send signals to other neurons on this slide Focus um and that's acetyl choline and norepinephrine the most well-known examples of neurotransmitters are acetylcholine and nor epinephrine on this Slide N mention acetal Colin esteras it has the capability to break down acetal Coline so from this slide again acle choline esterase has the capability of um destroying the structure of acetal choline or breaking down acetal choline this slide shows us an illustration on where pre and post synaptic terminals are located neurs this slide talks about neuronal Pathways also known as converging this basically how neurons are arranged potic terminals neurons preap terminal and other stuff like that a converging pathway is when two or more neurons serve as a preoptic terminal and send signals to the same neuron having only one post syap terminaling paway only one neuron makes a preoptic terminal but it's sending a signal to multiple neurons with multiple post synaptic terminals this slide illustrates to us a converging versus a diverging pathway so converging diing per multiple neurons receive so the diverging pathway is kind of like me in our group chat anouncement so that's an example or that's a metaphor for the diverging pathway this ends part one of our discussion on the nervous system in this recording discussion to part two this presentation contains part two of our discussion on the nervous system in part one we focus mainly on neurons their structure or their microscopic anatomy and how they communicate with one another here in part two will'll look into the gross anatomy of the CNS and pns including their parts and their functions just a recap the nervous system is divided into the Central and peripheral um nervous system the central is physically composed of the brain and spinal cord while the peripheral is composed of all the other nerves extending um to the outside of the brain and spinal cord on this slide let's look at the gross anatomy of these spal cord Sim Magnum second lar vertebra spinal cord so this is protected by the vertebral column which is a component of the skeletal system capability to move our torso is thanks to the nerves on our spine now any damage to the spinal cord could lead to paralysis spinal cord inj affected areas of paralysis if for example a person damages um or obtains damage from their L1 then all the other areas below thaty all right if the damage occurs at a much higher location let's imagine at the third vertebral um or third cervical vertebra or n no then they wouldn't be able to move their shoulders their arms lower torso up to their legs now why is thatas get affected because the brain is located Superior to all these places so if you cut off the connection to the brain then brain to send action potentials or control the motor division of all these muscles below we've already talked about this in part one there is what is known as the gray matter and white matter the gray matter doesn't have a lot of myelin and as we can see right here the gray matter is located in the middle of the spinal cord in a butterfly shape or um letter H shape Arrangement you white m po it contains a lot of myeline and this is seen on the outer areas of the spinal cord based letter H shape gray matter different areas also houses neurons that serve different functions in the nervous system the posterior horns contains axons that communicate with interneurons anterior horns have somatic neurons lateral horns have autonomic neurons and in the middle is a central Canal filled with fluid so mamayo will further discuss what we mean by somatic autonomic as well as the purpose of the fluid in the middle this slide shows us where each of the horns are located and what types of neurons can be found in each horn let's now talk about reflexes reflex is an involuntary action all right so reflexes um this is something but this is a response to a stimulus that has been applied to the periphery and transmitted to the CNS so basically my stimulus receive and this was sent to the central nervous system reflexus allow a person to react to stimuli more quickly than is possible if conscious thought is involved so reaction time if you reflexes not involved instead of us still having to through um the the act of making a conscious decision to something all right so for reflexes no um we could kind of say that this is something that involuntarily happens or as mentioned in the first bullet this is an involuntary reaction we don't have to think about this it just happens as a response to stimuli a reflex arc is the neuronal pathway by which a reflex would occur and has five basic components so let's um take a look at those five steps on how a reflex arc would happen here are the five easy steps on how stimuli is processed to produce a reaction um but yeah that's how it is we call it the reflex arc and it's basically the steps on how stimulite is received and processed to make a reaction so number one a receptor would or sensory receptor would receive the stimuli number two a sensory neuron would process that information it and then pass it on to interneurons in the form of chemical signals or action potentials um number three interneurons would receive that information um number four um it is then sent to motor neurons which are mainly responsible for communicating with muscles until finally number five um it would reach the eector organs or the organ that needs to react to the stimulus okay so steps inter neurons then we would refer to that as the simplest reflex arcs here's an illustration on how reflex arcs would happen if sensory receptor would receive the stimuli a sensory neuron would process and send that to the inter neuron the inter neuron would then send it to a motor neuron um then this motor neuron would send that processed information to the affector organ and then the affector organ would react accordingly okay so it's interesting to note that but for the nervous system all these processes would happen in less than a second the stretch reflex is when the muscles contract in response to a stretching Force so stretch muscle that's why it's reacting that's the stretch reflex the kneejerk reflex is an example of a stretch reflex so basically um a medical professional would lightly hit a person's um patella or knee bone with a reflex Hammer which looks like this and then they would observe how the person would act next is the withdrawal reflex also called the flexor reflex it's to quickly remove a limb away from a painful or shocking stimulus so table you'll move your hand away you'll move your hand away even quicker all right so these are examples of withdrawal reflex you literally withdraw a body part away from from the source of stimulus this illustration shows us how a withdrawal reflex would work in relation to the reflex arc that we just talked about earlier let's now talk about the brain the brain is the most important organ in our body and that's according to the brain itself but um we'll get to that later now we'll understand why and how did the brain become so important the brain has four major regions the brain stem cerebellum dipylon and cerein let's first look into the brain stem it is divided into three components the medola oblongata Pon and midbrain the Medela oblongata is continuous with the spinal cord again the specific segment that connects the brain with the spinal cord is the medulla of longa so listed here are its functions this part of our brain controls our heart rate it could contract or dilate blood vessels it controls our breathing so we don't have to consciously think about it the Mida oblonga mostly controls things that should happen involuntarily like coughing sneezing keeping our B the pon is located above the medala and it is the bridge or connection between the cereum and cerebellum so the ponds also helps to control breathing it also helps us with things that we need to be able to do when we eat like um chewing salivation and swallowing and cere and cerebellum relay station or Communication Center for the cereum and cellion the midbrain is right above the ponds and it works to coordinate our eye movement it also helps with adjusting our pupil diameter so for example the iris of the pupils will close or become narrow so that less light would come in the iris of the pupils will open wider in an attempt to let more light in um certain emotions could also influence the movement of our Iris and pupils so the midbrain also has something to do with that um as we can see right here turning the head towards a noise is also the work of our midbrain so and you direct your attention to that no that's a combination of your midbrain doing its job and also this slide talks about the other components of the brain stem such as reticular formation so this one does not have a specific location rather it is scattered across the brain stem and listed here are its functions let's now look into the cerebellum the cerebellum is attached to the brain stem and the attaching structures are called cereb pedal the term cerebellum actually means little brain with how the cerebellum is shaped it has a cortex composed of gye suai and gray matter the cerebellum also works to control balance bra which also helps with balance the Meda ofata all right so listed here are the other functions of the cerebellum let's now move over to the dipylon so the dialon has three components the thalamus hypothalamus and epithalamus the thalamus is the largest part of the dianon the thalamus Works to regulate or control the sensory input spinal cord and brain stem papasa cereal cortex this is also the part of our brain responsible for moods so very acus the epithalamus is just right above the thalamus the epithalamus is what's responsible for our reaction to smell as it says right here it's for the emotional and viseral response to odors so and it reminds you of a place or a person or food or your childhood then that's your epithalamus working another example is something um that's a reaction that was also brought about by your epithalamus the epithalamus also um houses what is known as the pineal gland the pineal gland is a part of the endocrine system the hypothalamus is located below the soap arrangement we have the thalamus the largest part of the Dion Thalamus is the epithalamus hypothalamus so the hypothalamus mainly controls the pituitary gland further when we get into the endocrine system the structure that connects the um hypothalamus to the pituitary gland is known as the INF deul and listed here are its functions this slide shows us an illustration of all the structures that make up the dlon let's now talk about the cereum the cereum is the largest major segment of the brain and it is divided into the left and right hemisphere the space in between them is called the longitudinal fissures so this photo right here shows us the different loopes the cerebral cortex is at the surface of the cerebrum which is composed of gray matter again what is gray matter these are nervous tissue that has very little amounts of myelin uh this is the part of a brain that is responsible for thinking and communicating so cereal cortex um the cereum is also the part of our brain that helps us remember understand and make voluntary movement um I think for me personally very active cereal cinker understanding let us at the structures cereum the longitud fure divides it into the left and right hemispheres the G are folded areas or parts cve the suite are the shallow indentations or that go inward we would Now call those fisures so according to a publication from the research gate the number of soul soal pits in the left posterior inferior frontal sucus and the right posterior inferior temporal Solus was positively related to average IQ according to the psychologist um sir Rex Young from the University of New Mexico all of the wrinkles and convolutions on our brain allow more of that computational capacity to fit in so in other words and soul brain person the more wrinkles that they have in their brain no the more intelligent a person is so um with that information you could just say wow the left hemisphere of the brain controls the right side of the body the left side of of our brain has also been known to be the more analytical side capable of understanding and solving mathematical equations or M making sensible speech or learning a new language the right hemisphere controls the left side of the body and um this side helps us more on the things that require creativity like making music creating any art form or formulating abstract ideas but we got to understand though functions left and right hemisphere they would always be working together if for example you're making music where your left brain or um sorry your right brain would typically lead the way of course you still have to analyze which beat would be better to set the vibe of the song you'll have to analyze um the instrumental Arrangement and other technical stuff like that same with the left brain all right so for example I am trying to learn a new language a little bit of creativity might go into the process of how I would remember new words okay so the left and right hemisphere for the most part usually always works together the structure that connects the left and right hemisphere is called the Corpus eloss the frontal Lo of the brain controls voluntary M functions or you movement muscles that we have to consciously think about for them to happen all right so the frontal Lo also influences our mood and this is the site of aggression so something WRAL cortex um the parietal lobe is located at the top and it mainly Works to process sensory in input such as those that are listed right here the occipital Lo is located posteriorly or at the back of the brain and controls our vision or our eyes the temperal lobe um the temporal loes are at the sides and their function involves hearing smelling and memory this photo shows us a superior or top view of where each hemispheres and loes are located let's talk about speech first is sensory speech which is processed by the WX area this is located at the parietal loobe so WX area but this is where comprehension of the words we hear would happen so area um next is motor speech which is is processed by the brockus areas that's located at the frontal Lo this is where words are formulated so before we actually say them they were first pieced together at the broas area now how are disorders of the brain diagnosed with the help of the electro inogram or EEG doctors would be able to um monitor the electrical activities of the brain listed here are the different brain waves now now observed scientists using the electroen so alpha waves are produced by people when they are awake but also quiet beta waves are seen during intense mental activities delta waves are observed during deep sleep and theta waves are typically observed among the brains of children this slide shows a person having an EEG test let's now talk about memory the term working memory is when the brain stores information only for a very short period of Time person for the current task that they're doing so an activity is involved shortterm REM shortterm memory lasts a bit longer in comparison to working memory so an information is stored in the brain for a few days at maximum there are short-term memories that are eventually converted or that eventually become long-term memories brain information this happens by consolidation so when we say consolidation this is a gradual process where new connection and stronger synaptic connections are created or they're being formed in between neurons so longm declarative memory also known as explicit memory keeps information like names dates places and even emotional cues so generally declarative memory handles facts and feelings procedural memory also called reflexive memory involves uh motor skills like driving doing sports playing instruments so in other words muscle memory on this slide is what the lyic system does so the lyic system influences long-term declarative memory and also emotions and visceral responses to emotions plus motivation and mood so mostly the intangible things orus liic system lyic system this illustration shows us the physical or structural components of the lyic system let's now talk talk about the coverings of the brain and spinal cord called the menes um the outermost is the Duram mat and since first physical um line of defense of the brain and spinal cord this would also be the toughest layer the second layer is the arachnoid matter the space between the dura and arachnoid is called the sub Dura space so literally this is a space under the Duram matter the third layer in the menages is the patter which is directly attached or tightly bound on the surface of the brain and spinal cord so patter brain and spinal cord take note matter aroid so this is called the subid space located blood vessels that would Supply the needs of the brain and spinal cord these illustrations show us the location of all those menages and spaces the cerebral spinal fluid or CSF is a fluid that is um produced by epinal cells and this serves to provide um a fluid cushion to the central nervous system but directly directly umou or against the vertebral column and the skull components CNS so the brain and the spinal cord so menes fluid that surrounds the brain and spinal cord so that they have something to float on skeletal system that is surrounding them what talking about the autonomic nervous system it controls the involuntary squad or smooth muscles um cardiac muscles and glands so as it says here they are controlled unconsciously so or S they will just move as necessary thanks to our autonomic nervous system the autonomic nervous system is divided into two the sympathetic and parasympathetic division sympathetic division helps us with physical activities so a person decides to go running running naturally requires a KC muscles to work twice as hard so the sympathetic um autonomic division would handle that parasympathetic activates um totally involuntary functions like digestion or things that should happen even without the stimuli of physical activity the anic nervous system is composed of neurons located at the wall of the digestive tract so comp digestive tract when we start discussing the digestive system now um for the part of the anic nervous system it has different types of neurons the sensory neurons connect the digestive tract to the CNS the sympathetic and parasympathetic neurons would connect the CNS to the digestive tract so pabal Direction Sensory neurons and then of course the anic neurons are located everywhere else on the inter plexuses or the inic area this ends our discussion in both part one and part two of the nervous system for upcoming quizzes please see the recently posted schedule on our teams chat and for any questions related to this recorded discussion comment below Char you um again for questions related to this recorded discussion you may send me a direct message on the Microsoft teams chat all right so this has been Professor oel Enriquez thank you so much for listening