Chapter 10 Muscle Tissue Part3

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Chapter 10 Muscle Tissue Part3

here in this this idea of a motor unit so a motor unit is where a single motor neuron attaches to a particular number of muscle fibers or muscle cells right so where if one motor neuron attaches to many muscle fibers or muscle cells simultaneously that it’s going to lead to a stronger contraction if one motor neuron only attaches to one muscle cell or muscle fiber it’s gonna be a much weaker contraction we call these motor units it’s the idea of recruitment so that your your nervous system when you want to control a muscle you don’t that and activate the entire muscle all at once because that wouldn’t make a lot of sense right like would you want to contract with full force the entirety of your muscle for everything you ever do no exactly like what if you’re gonna I don’t know like write notes or something or type on your computer you wouldn’t want to use all the potential muscle force just the type or right no it’s right see there’s need to be a way to control like fine motor movements and gross and and more strong motor movements right this idea of a motor unit so if a motor unit is where one neuron or motor neuron attaches to any given numbers of muscle fibers that we call it the motor unit so large motor units are gonna be where you have one motor neuron attaching to many muscle fibers so when that one motor neurons active you’re gonna activate lots of muscle fibers which things you which means you’re gonna get a stronger contraction so you’d use larger motor units to like you know weight lift and stuff small motor units I found the only example that wasn’t serious yeah you’d use smaller motor units which is where one neuron attaches to just a few muscle fibers or cells and it’s gonna produce a weaker contraction you guys imagine a circumstance where you might want to use like a small motor unit like that yeah putting a thread through a needle right the things a lot of lights are sort of fine motor control and you want to just have nice little tiny contractions to get that thread right through the needle right otherwise if you use the full forcing your muscles like you never to get that through gonna be like Hulk like just frustrating like uh so once that motor neuron is active it will always lead to a contraction in a muscle cell we call this at all or none principle ok so if you if you activate a motor neuron it will lead to a muscle contraction so what we’re seeing here you guys it’s different motor units we got the blue and red ones so we have one red motor neuron here you can see that this axon branches out attaches to multiple muscle cells whereas the blue motor neuron here branches and only attaches to you know two muscle cells so which one which motor neuron do you guys think would produce the most force yeah the red motor units right it’s a larger motor unit and then would produce less force would be the blue one it’s a smaller motor unit because it attaches to less muscle cells and it turns out you actually recruit the smaller motor units first so when you go to like use a muscle you’d start with the small motor units and then you work your way up to the large ones and it makes sense right you wouldn’t want to start with the with the large ones and then work your way to the small ones because that means like if you’re gonna like grab a grab a coffee cup or something you’d start with the full force of your muscle yeah and then it would get weak and then you can go like okay that would be a very effective to like drink coffee yeah so you start with the smaller motor units first and you work your way up to larger ones make sense so this there’s also an idea of muscle tone the physiological mechanism of muscle tone is different than what you guys hear about muscle tone you know on TV or something you hear about muscle tone like muscles being toned or like you’d feel like well study you like devices to make your muscle tone right like oh you so tone your muscle okay now that forget that okay it’s that has nothing to do with this mechanism so the physiological mechanism muscle tone is where muscle cells are always a little bit active they’re never fully relaxed they’re always a little bit active there’s a slightly contracted keeps the muscle cells healthy they always being like a slight state of contraction it also prepares them and keeps them ready for a mouse muscle contraction when it needs occur okay so muscle tone is actually have feedback mechanism where the tension of a muscle cell is measured by neurons and then that actually goes to the spinal cord and then actually can activate another motor neuron that can excite the muscle cell to contract and it’s a cut at this constant or steady state of contraction that your muscle cells undergo even when you think they’re relaxed like if I have

you guys like point to a muscle in your body and even if you think it was relaxed I’m not currently contracting it’s actually still slightly a little contracted that’s muscle tone and so what a kippah muscle cells healthy ready to contract okay now there’s two different types of muscle contraction we have isometric and isotonic ISO means the same what you guys think of metric what does that bring to mind yeah distance exactly and then tonic means tone like a steady state of something right so isometric means your muscles contracting but not changing length you have to have an example like an isometric contraction where it’s contracting but you’re not changing the length of that muscle all right so we were seeing here guys she’s able to pick it up but if her muscles not changing length then we call that isometric but if your muscle is contracting and it’s shortening we call that isotonic specifically con centric good you know what about if she went back down and put it back down to resting position eccentric but it’s silk isotonic good now there’s also different types of muscle fibers within muscle not all muscle cells are the same we got slow oxidative fast oxidative and fast glycolytic fibers so oxidative phosphorylation is where your cells can use oxygen to help generate ATP right glycolysis is a form of anaerobic respiration where our cells just make ATP in the absence of oxygen okay so if it’s an oxidative type of fiber it means it’s relying heavily on an oxygen supply if it’s glycolytic it means it’s not relying that heavily on oxygen and it said relying on just ADP production in the absence of oxygen okay name I wonder why have different types of fibers well you use your muscles differently not all the month not all the muscles in your body you’re gonna use the same way right like some muscles need to be really fast you need to have like really powerful bursts of quick energy right other muscles need to be more like endurance type of muscles right like postural muscles need to be able to endure the length of an entire day of sitting upright or standing right so those would be more of the oxidative variety because they can produce a moderate amount of ATP over a long period of time okay really quick bursts of energy where you can’t really supply oxygen to your muscle tissue that would be more like the glycolytic fiber right because you don’t need oxygen here right you’re just producing ATP really quickly in the absence of oxygen so what types of muscles do you think will be well-suited for for fast glycolytic fibers yeah leg muscles especially if you’re a sprinter like we trained yourself to Sprint’s you know really quickly you know for a short period of time you’re gonna find much more fast glycolytic fibers there or if you’re a long-distance runner oxidative slow or fast oxidative right but the ox at least the oxidative variety because over if your long-distance runner then you can you know keep up with your ventilation and you can inhale oxygen and help to make ATP over a long period of time those are oxidative fibers now if you have a glycolytic type of cell and muscle do these cells need a whole lot of blood supply if they’re not relying on oxygen no right because it’s a blood that brings in the action so you gonna find less blood vessels and glycolic fibers you also find less myoglobin myoglobin is going what gives meat that kind of brownish reddish color and so would you find a lot of myoglobin if an if it holds oxygen would you find a lot of myoglobin and glycolic fibers no so glycolytic fibers are the white meat because white meat is what lacks myoglobin and by not having my own globin the tissue looks white red meat or dark meat has like myoglobin which is involved in storing oxygen and that’s more found in these oxidative fibers so where do you find like white meat on an animal of some sort v ya chest like do ya thing like a bird right like chicken breasts is white meat well what our chickens use their breast muscle for flapping their wings right and they can do really quick bursts to get away from a further or something right so they have quick bursts of energy they can flap away but then see like black oh it’s the fast glycolytic fibers why are they white they don’t myoglobin and so that has less myoglobin so it makes it look more white and then where do you find like red meat or dark meat you mean like on the actual leg itself I was thinking more like the trunk area you have a lot of these oxygen fibers because they’re better for endurance things like

postural support that makes sense now what’s interesting you guys is that these fibers can change type depending on how you use them so if you if you change the way you use a muscle you can change your fiber type so like what it’s say let’s say if you took up sprinting as a hobby you could somehow generate not new fibers but your fibers can change from one type to another like you can you can alter your oxidative fibers into the glycolytic variety or what if you would from sprinting to like longest to swimming well then you can change your glycolytic fibers back into the oxidative right just kind of cool so what this table here shows you guys is the comparison of these oxidative fibers and glycolytic fibers now if it’s slow versus fast this refers to differences in the speed of the myosin head so if your myosin heads contract more slowly that’ll make a slow fiber if they contract more rapidly that’ll make a fast fiber and so then these muscles will produce tension at varying rates so slow oxidative fibers produce tension more slowly right fast oxidative fibers Prue’s tension more quickly and it’s all dependent on the speed of that myosin ATPase okay now if it’s oxidative where does it skip where’s it gonna get its ATP from it’s getting its ATP’s from mitochondria which use oxygen to make that ATP right so we actually find that you know you have higher capacities to make ATP in these oxidative fibers and then if it’s glycolytic you’re getting ATP from glycolysis which is a very limited form of ATP production which basically break down sugar and that gets that get you some ATP based on that sugar breakdown but it doesn’t require oxygen so we call that an aerobic or glycolytic okay so what about blood vessels in that muscle would you need a lot of blood vessels in the glycolytic variety no because you know you don’t need as much oxygen supply to those tissues what about oxidative yes definitely good how about the color of the tissue in the glycolytic gray white right that’s the white meat and then what about if it’s oxidative dark it’s red you guys once it’s red because myoglobin is rich in iron and iron oxide looks red that’s why they call it Colorado by the way because our dirt here has is really rich in iron so gives it the red color which is also why our Bloods red because it has a lot of hemoglobin like myoglobin transports oxygen on iron now what about contraction velocity if it’s a fast fiber fast yeah and what does that relate to if it’s fast what makes it fast the speed of your Madison head right so it’s the speed of the madison ATPase right now you find these fibers in different areas so you find slow oxidative fibers in muscles of the trunk like postural muscles because these will they’re better for endurance you know holding your trunk uprights over the course of a day is an endurance activity you know if this was a fast glycolytic variety what that means it is you can hold your trunk upright really well for short periods of time but then they would get fatigued and then you’d fall over you get to wait there until your muscles weren’t fatigued and then you’d stand up again and be like okay I’m standing that’s good and then you get fatigued you’d slip over again so it makes sense to have a slow oxidative right it’s better for endurance activities they’re the slow Exadata fire fibers are the smallest diameter the fast glycolytic fibers have the largest diameter and it relates to the amount of myofibrils you find in said cell and if it’s glycolytic do you need mitochondria we don’t need as many because remember mitochondria use chemicals and oxygen to help make ATP but if it’s glycolytic are you relying on oxygen no exactly so then you don’t need as many mitochondria in the glycolytic variety which is also one of the reasons why they look more white because they like they’ll act as much mitochondria which look kind of brown if that makes sense and then where do you get we’re gonna find a lot of myoglobin if it helps hold on to oxygen slow and fast oxidative right if they’re oxidative then they’re using oxygen to make ATP and so if it’s slaught today this is better suited for endurance fast oxidative is better suited for like medium duration things like walking hiking fast glycolytic is better suited for quick bursts of energy think like sprinting right what is it saying lifting weights to like power lifting that’s your thing you like the power lift you have a lot more fast like oolitic fibers right if your thing is the more like you know take five hour walks then you’ll have slow oxidative fibers don’t make sense all right guys so what

this picture is showing is the difference between these so if they’re lighter what are they lacking myoglobin if they’re darker they got lots of myoglobin in fact you guys see this muscle has a mixture of all of them so when you think about like in terms of entire muscle they’re all like white meat or dark meat you’re not gonna have one type of fiber in that that muscle it’s actually gonna be a mixture of fibers but if you predominantly have the fast glycolytic variety in that muscle it’s gonna make the muscle tissue look lighter right so in fact nope no muscles gonna have one type it’s gonna be a big mix of fiber type so you have slow oxidative fast oxidative fast glycolytic and what’s cool is these fibers can switch their type you can switch from a fast like oolitic type to maybe a fast oxidative or slow oxidative do a fast oxidative and so that that switching is dependent on how you use the muscle remember back in boom we talked about how bones will mold and change based on how you use them we talked about how like bony protuberance bony parts can get larger depending on how how much you use that right like the external occipital protuberance and your occipital bone can get larger if you use your trapezius more well depending on how you use a muscle you’re also gonna change your fiber type so make sense now what does it say you guys is that skeletal muscles you should contain all three muscle fibers a single motor unit usually controls muscle fibers of the same type and so that means you can actually recruit different motor units to only activate certain types of fibers slow fibers you find in postural muscles like your back and calf and those are mostly you have like a continuous state of contraction and there are no slow muscle fibers and muscles that require swift’s but brief contractions that make sense and I’m like that like in the eye and hands like if you’re gonna move your eyeball around those are only fast fibers not slow fibers because what would happen if your eye muscles were slow fibers not just Li Zi but your eye ball would move much more slowly right like imagine hearing a noise and then trying to look look at that where the noise is coming from and your eyeballs are going right just very slowly and like that would be very effective especially if you’re trying to survive like it’s a predator or something yeah slow mo exactly no we talked about how if you don’t use it you lose it right same thing in muscle if you don’t use muscle it atrophies just like bone does and if you overuse muscle then it’ll hypertrophy just like bone nuts so muscle atrophy is a wasting of muscle tissue that reduces the size tone and power of muscle it can come from a lack of stimulation whether it’s under use or damage to nerves that connect that muscle hypertrophy is an increase in the muscle fiber size that results from repetitive stimulation of muscle fibers so you hear about people like you know they want to bulk up what their muscles look bigger so then they go out and use it in some way but they sell those devices the reason why I say that is they sell those devices that like might shock your muscles so you could be lazy and just like Lander couch you know have this little device like shocks your muscles and you can like sit back and like just watch TV well it shocks your muscles to contract that way you get a 6-pack the laziest way to gain muscle ever tomorrow huh apparently apparently yeah and I would I would be I would be surprised if it also gave like an even type of muscle thickness you know I kind of doubt that you’re evenly shocking all your muscles so probably probably cause your your abdominal muscles to look more lumpy yeah they’re not evenly using them you might get like one big little lump right and then one big lump right there like check out my six-pack just looks lumps no skeletal muscles are they’re defined based on their the basically the shape of their fibers so like fibers can be in circular arrangements they can be parallel they can converge or the new Penates so if they’re circular that should kind of form a circle like around the mouth so orbicularis Oris would use for kissing and kind of puckering your lips that’s a circular muscle parallel muscles include like your rectus abdominus like your six-pack here convergent muscles include ones like your pectoralis major where these muscle fibers converge unto an insertion and then Penn eight is where they kind of fan out like a feather and you’re gonna find this commonly like in forearm and leg muscles they’re more Penn eight now in terms of different types of contractions and skeletal muscles we have agonists antagonists and synergists an agonist is a muscle that produces of specific movements so back when we talked about the movements of your synovial joints we said feathers like you know we had a abduction and

adduction and flexion and extension and Piper’s we had supination and pronation and inversion e-version right and lateral rotation and medial rotation well the muscles that do those actions there’s an agonist for that so we’ll learn about this later but there’s like flexors of your forearm or there are flexors of your wrists those are agonists for that particular action or activity or there are abductors of your thigh or adductors of the thighs those are all Agadez they perform that specific action now antagonists are ones that actually oppose the action of an end some persons what’s the opposite of flexion extension okay and then what’s the opposite of abduction and then the opposite of inversion there’s that would be antagonist so if you talk about how those flexors of your arm then an antagonist would be extensors of your arm so the flexors are garment looking like biceps brachii brachialis extensors of your on would be like triceps practicing back here and synergists are muscles that actually can perform the same action so there’s not one muscle to perform one action it turns out those mini muscles that have to perform the same thing so for instance you guys an example of flexion on the arm right there’s not one flexor muscle on your arm there is multiple and that would be a synergist cuz they help perform the same action now the net the way that muscles are named is based on their action where they’re found where they’re attached to what they look like their size shape and how many heads are tendons that they have okay so once we start getting to muscles next week like identifying ones in the lab we’ll learn about how the muscle names are based on any of these categories right so there’s one called orbicularis oculi we think of oculi what comes to mind alright orbicularis sounds like an orbit or kind of circular like an org right so orbicularis oculi is a circular muscle that surrounds your orbit it’s involved in kind of like you know squinting let make or what if there’s one called sternocleidomastoid named him for the bones it connects to sternum clavicle and mastoid process you got it so that’s cervical it a mastoid attaches right there it’s on your neck yeah it’s a big neck muscle there yeah or what if there’s one called pectoralis major well that’s on the chest yeah I’m not sure well there’s no one to you guys it’s much higher on your list but it’s just kind of interesting is one called piriformis piriform means pear-shaped because this muscle looks like a pear it’s kind of shaped like a pear that’s piriformis it’s in your gluteal area in fact gluteus maximus right the gluteal region is your behind right so the gluteal muscles they’re named for that particular region make sense right or there’s another one on your face called zygomaticus so psycho madness major and minor guess what bone they attach to you like a magnet exactly so they’re named based off of their region what they attach to or what they look like or the direction of their fibers so keep that in mind as you guys to go through the muscles because this will help you tremendously as we go these muscles if you think about what the name means it’ll help you learn okay so what this slide shows that are just sort of muscles that are named by action specific body area attachment orientation shape and size or muscle head so just kind of keep this stuff in mind as you go through the muscles and it’ll help you learn much better now we’re just gonna wrap up this chapter you guys talking about cardiac versus smooth muscle so where do you find skeletal muscle attached to bones skin or other muscles right so where do you find cardiac muscle the heart and smooth muscle hollow organs like digestive tract respiratory tracts genitourinary tracts what’s that oh that’s good for this yeah so which of these three are voluntary skeletal right which ones are involved cardiac and smooth which ones are striated skeletal and cardiac good which one do you find the walls of hollow organs smooth alright really guys so they’re all involuntary there are some skeletal muscles that are involuntary

though yeah you make a good point so urinary tract muscles although you have smooth muscle in the wall of your bladder in other areas of your area tract if you’re intentionally urinating it’s not because you’re consciously controlling smooth muscle you’re actually controlling skeletal muscle that helps you urinate but that’s a great question so cardiac muscle you guys finally find the heart and you find it the heart wall its striated the cells have one or two nuclei in a formal Y shape all these cells are linked up by intercalated disks which are full of gap junctions what was the function of a gap junction communication between cells nice and these cardiac muscle cells are also autorhythmic which basically means they can generate their own action potentials in the absence of your nervous system so it means your heart can beat without nervous system stimulation okay now they’re under involuntary control which means you can’t consciously control your heart rate you can change your emotional state change your heart rate like give me meditate or think about something that’s maybe exciting to increase your heart rate but you can’t like tell your heart to stop or tell your heart to go faster right if you just change your emotional state to do that but that’s still involuntary so what cardiac muscle cells look like is they’re short they’re branched and they’re striated it’s these stripes or the striations they’re also linked up by intercalated discs which we see here these intercalated discs are basically big aggregations of gap junctions which allow for currents to spread from one cell to the next okay now these cardiac muscle cells typically have like one and two nuclei and it’s only found the heart now you’re still gonna find sarcoplasmic reticulum instead of a cardiac muscle cell you’re still going to find myofibrils you’re still gonna find thick and thin filaments so the way they could tract is identical to skeletal muscle but there’s excited differently so skeletal muscles excited using neurons from your brain or spinal cord that then shock it right cardiac muscle can actually contract on its own is it it doesn’t need the nervous system to tell it to contract it actually can generate its own rhythm of electrical currents that’s on rate okay now smooth muscle you find in the walls of hollow organs like visceral organs so I just subtract urinary tracts reproductive tracts and respiratory tract you also find it in blood vessels why might you want smooth muscle in your blood vessels yeah we were interesting yeah to control body temperature so back in skin we learned about how smooth muscle and your blood vessels of your skin can change the shape of a blood vessel to regulate body temperature right so if you’re a hot what are your blood vessels do and days of dialing which can increase blood flow so that’s relaxation of the smooth muscle in that vessel or if you’re cold you could have basil constrict which reduces blood flow to skin that we can preserve your body eat now these cells are short they say fusiform which is kind of mean spindle shaped they have one nucleus no striations that’s why they call it smooth we have thin filaments that are attached to something called dense bodies so there are no sarcomeres in smooth muscle cells they contract differently they don’t contract using sarcomeres they contract using kind of an otter like a more odd arrangement of of thin filaments or actin filaments okay and they’re also under involuntary control so you can’t consciously control smooth muscle so if you look at a smooth muscle cell it’s kind of spindle shaped we have a centrally located nucleus this is what the sarcomere kind of looks like in a muscles a smooth muscle so you see it looks much more differently right so you fight you still find a thick filament thin filaments but they’re arranged in different patterns and instead of shortening the entire muscle actually causes smooth muscle cells to kind of clump up so these smooth muscle cells clump which means they’re really good at squeezing things so it makes sense like if your digestive tract needs to squeeze food forwardly these new muscle cells can do that and if your blood vessels need to help constrict and prevent blood flow to different parts your body you know smooth muscle cells can do that too and we’ll talk more about this you guys in future chapters and anp2 so this is a comparison of skeletal cardiac smooth which ones these are striated skeletal cardiac which one do you find in the walls of hollow organs smooth good and which one is voluntary skeletal which one you only find your heart okay which one is branched cells cardiac which one doesn’t have sarcomeres smooth good which one has unbranched cells that are striated skeletal which one has many nuclei skeletal because skeletal muscle cells can be up to like feet in length good

which one is very short cells cardiac and smooth have very short cells okay so just came to get some comparisons and contrasting information of these muscle types