all right we're gonna be looking at chapter 10 now with the muscular tissue so a quick overview when we talk about muscular tissue the motion is going to result from muscles contracting and then relaxing my ology is the study of muscles and there are three types of muscular tissue which we discussed back in Chapter four so when we look at these three tissues they're smooth skeletal and cardiac and when we look at picture a this is going to be skeletal muscle B is cardiac and C is smooth so let's take a little closer look at comparing these three so if we look at an overview of skeletal muscle it is an elongated multinucleated striated cell it's going to be unbranched it's gonna attach to bones via ligaments this is why they're your skeletal muscles which make your bones move they're very large and their diameter and length they do have sarcomeres and this is what gives them that striated structure they're contraction speed is fast they're controlled voluntarily by your somatic nervous system but regeneration and your skeletal muscles is very limited on the other hand for cardiac muscles those cells are also elongated but they're United with one nucleus they are also striated because they have sarcomeres they're branched they have intercalated discs and these discs have gap junctions so that these cells can communicate and contract all together in unison this is going to be found in your heart their diameter and length is still pretty large they have a moderate contraction speed their control is involuntary by the autonomic nervous system and again their regeneration is limited now for smooth muscle will see that they are tapered their unit nucleated and they're not striated at all the walls of your hollow organs are going to be made up of smooth muscle as well as the erector pili in your skin their diameter and length is small again they do not have any sarcomeres their contraction speed is slow and they are also controlled involuntarily by your autonomic nervous system now these do have a considerable amount or ability to regenerate compared to skeletal or cardiac muscles but it's still very limited if you compare it to other tissues like epithelial to so what's the function here of like the muscular system well it's to produce body movements like running and walking this is going to be your skeletal muscles we also see that it's going to help stabilize your body positions like sitting and standing again skeletal muscles are going to help with this it can stay can store and move substances throughout your body so we have some examples here like sphincters they open and close and so it's it's going to be muscle cells that either open or close a area where we can actually move the contents from one area to the next like from your stomach into your intestines or from your urinary bladder out and this is gonna be smooth muscle we also see that your Harpeth heart is going to pump blood moves flute food through your GI tract and it aids in returning blood to your heart and this is all going to be a combination of cardiac smooth and skeletal muscle we also see that it produces heat this is called thermogenesis the whole point of shivering is to cause your skeletal muscles to generate heat and warm your body now characteristics of muscle tissue is they are excitable example of excitable tissues or cells or muscle and nerve cells they respond to stimuli and they create action potentials electrical impulses we see that they also are contractable they usually shorten in length when they're stimulated so they contract okay in that process we also see that they can be stretched so there is extensible they are gonna have some elastic to them so they so they're gonna return to their normal shape after they contract all right so let's look at the gross anatomy of a skeletal muscle and I remember gross here is going to talk about large-scale anatomy all right so we're gonna look at the levels of organization and we're gonna start first with the chemical level because that's what we start with when we're working our way up then we're gonna look at the cells the tissues and then the organ itself so when we look at the chemicals that are part of the skeletal muscle these are what we call myofibrillar these are made of protein myofilaments known as actin and myosin and they are gonna form the sarcomere structure that we see in skeletal muscles the cells of a skeletal muscle are known as muscle fibers the muscle fibers get bunched together with connect tissue around them and these are called muscle fascicles and then of course the whole thing with all the FAFSA calls packaged together create the muscle itself all right so we see here you have your muscle fiber which is the cell a bundle of these cells is a fascicle and then many of these fascicles together make the whole muscle now when we look at the muscle as a whole as this organ there's gonna be some connective tissue in here with that muscle tissue we see that they're going to be tendons present tendons again are dense regular connective tissue they attach muscle to bone okay and when we look here they're going to be extensions of the EPI and peri and endo myosin all right and so we do see that there's going to be extension connecting the muscle to the bone we then see there's what we call the deep fascia connective tissue this is the outer muscle covering alright so you can see that here it's the outer muscle covering when we move in we have what we call the epimysium the epimysium is connective tissue that's a sheet that directly surrounds the entire muscle so it's going to hold the muscle together so we have the deep fascia and just inside of that you have the epimysium we then have the para myosin the para myosin is going to surround a bundle of muscle fibers that we call the fascicles so they cover the fascicles and then you have the endo myosin which is also going to cover individual muscle fibers the whole point here is to insulate so that they can conduct their action potentials so that the fibers can contract now if we look at this it's almost like wrapping a present multiple times okay so we have the muscle fiber itself and it's gonna be wrapped in a layer of endo myosin then we're gonna take a group of muscle fibers that have been individually wrapped and we're gonna rock them again with the para myosin then we're gonna take a group of those fascicles that have been wrapped in para myosin and we're gonna wrap them with the FO - in and then we're gonna wrap it again with the deep fascia so you can notice that it's got multiple layers wrapped around these muscle cells so guys will we look here the nerves are gonna stimulate your muscles to contract and they're going to do this through electrical impulses or what we call action potential Jools action potentials are carried by somatic motor nerves when we're talking about the skeletal muscles so we see that there's going to be some sort of stimulus that's going to come down through the nerve and it's going to cause some sort of response by the muscle and that's going to be a type of contraction now these effector skeletal muscles are controlled by the somatic nervous system so this is a voluntary type of movement now if the effector is smooth they're cardiac muscle or if it's talking to glands this is going to be the autonomic nervous system so it's involuntary the sensory nerve neurons are going to send an input this is going to cause an afferent pathway up towards your spinal cord in your brain this leads to the central nervous system which is your control center your central nervous systems I'm going to decide what needs to be done it will then send a signal down the efferent pathway down the motor neurons this is the output the output is going to tell they've skeletal muscles what to do so in this case it's showing you an example you have a stimulus okay there's some sort of sharp object - that is coming into contact with the skin and so the stimulus is sent through the sensory neuron to the central nervous system it's going to determine what needs to be done and it sends a motor neuron output this then tells the skeletal muscle to move so if you were touching that particular a sharp object it was going to allow you to then pull your hand your arm back by contracting the bicep now your muscles have a good blood supply they contain abundant capillaries and this is important because they need to supply tons of nutrients and oxygen to these cells these cells are going to need to be able to produce high levels of ATP and we'll see why in a minute because contraction requires high levels of ATP or energy we also need these blood vessels to remove any of the waste products that are going to be made through cellular respiration all right so now let's look at the microscopic anatomy of the skeletal muscle okay so we went big picture how does the muscle look as a whole now we're going to get down into the actual actual muscle fiber and what we also call the sarcomere so the muscle fiber or the cell is multinucleated it's elongated it's a long cell that's cylindrical and it's going to run in parallel arrangement so they're going to run in this direction these are set that you have a set number before birth and these will typically last your whole life unless of course some sort of damage happens to them these are made up of what we call myofibrillar we see that there's a special type of plasma membrane that's covering these myofibrils it is karthik called the sarcolemma the reason this is special is they contain these transverse or t tubules that are going to go in between the different cells okay this allows for a quicker response to take place since these cells are so long you can find them here these are part of the plasma membrane these transverse tubules are associated with that sarcolemma we also see that it has a special type of cytoplasm called sarcoplasm this is going to contain mini mitochondria to help produce produce ATP ATP we also see that there's going to be an area for glycogen to be stored this is a stored type of glucose we also see mild globulin which is going to bind to the oxygen and hold on to it until it's needed and we also see that they have sarcoplasmic reticulum now sarcoplasmic reticulum is a specialized type of smooth ER this is going to store and release calcium ions which are going to be important for the sarcomeres contractions so you can see here the sarcoplasm which is the cytoplasm lots of mitochondria are present because of the high demand of ATP through cellular respiration and the sarcoplasmic reticulum is a modified form of the smooth ER containing those calcium ions now if you'll notice Sarco is in each of these so when you say Sarco as a part of the actual name it is going to pertain to a muscle cell we also see that the terminal cisterns are all going to be part of the sarcoplasmic reticulum and they run next to those transverse tubules which are part of the sarcolemma or plasma membrane alright so when we look at mouth Abril these are made of protein myofilaments that we call actin and myosin and these are going to be thin in thick filaments the thin filaments are known as the actin okay so we see that the myofibrillar we take it out of there we have the thin filaments which are the actin these have binding sites for the myosin but they are covered in this picture by troponin and tropomyosin we see that there are going to be seen as thin in the sarcomere in this picture you can see the thinner line is the actin the thicker line is the myosin these are the thick filaments and they have these special heads on them they kind of look like a double golf club these are going to be the myosin heads that are going to connect to the binding sites on actin and in the picture you can see that they are a thicker line in the sarcomere so a mile filament is going to be actin and myosin and they are located in compartments that we call the sarcomere a sarcomere is the contract wha the contractile units that contain thin and thick mill of filaments and you can see that here this is called a sarcomere so let's look at the structural arrangement of these myofilaments the actin and myosin so we see that there's going to be these z disks that are going to separate the sarcomeres okay so the zigzag type line that you see is the z disks they're gonna separate one sarcomere from the next we then see that there's an area called the eye band the eye band is the light band which means that there are the thin filaments only okay so this is going to be this section because it's a thin filaments only that are present so the eye band is the thin we then have the a band the a band is the dark band and this is going to be the thick filaments okay and so if you'll notice there are some overlap with some thin filaments here but anywhere there are thick filaments they're going to be part of the eye band the H zone is the area where only thick filaments are found and then the very middle part of the sarcomere is known as the M line this is the middle of the H zone and it holds the thick filaments together alright guys you need to understand these different structures of the sarcomere so you need to be able to identify the sarcomere picture as present where's the z disk the eye band the a band the H zone in the M line so now let's talk about the contraction and relaxation of these muscle fibers how does that sarcomere actually work well the sarcomere is going to work using what we call a sliding filament model this explains how the muscle fibers will contract relax so you know sarcomere you'll notice that the thin filaments and the thick melt filaments had some overlap what's gonna happen is these are going to actually move over each other and overlap more when the muscle is contracted shortening the muscle as a whole okay so if you'll notice my arms didn't get shorter just the space between them did okay then that's gonna relax and come back okay so we see that the contraction is gonna happen and relaxing so they're sliding over each other and this is where this model comes from so let's talk about each step so during relaxation the calcium is sword in the sarcoplasmic reticulum the myosin heads are detached from the actin so at Raths are just sitting there nothing is attached and the calcium is put away in the sarcoplasmic reticulum but when contraction needs to take place calcium is going to be released from the sarcoplasmic reticulum it's going to cause the sticky heads of the myosin to attach to the actin forming cross bridges so those little golf club type heads are going to be able to attach to those binding sites and they're going to actually pool okay this cross bridging is going to be hydrolyzed by ATP so the myosin head has an ATPase that's going to utilize the ATP and this process of binding and pulling is called a power stroke this is where the myosin pools on the actin fibers to shorten the sarcomere so during contraction sarcomeres do shorten but the length of the thick and thin filaments do not change z discs move towards the in line so here are a couple of questions to think about what happens to the width between the z disks okay so if we're looking here the Zetas what's going to happen to them well they are going to get narrower they're gonna get closer together because they're being pulled towards that M line what happens to the width of the H zone it's also going to get narrower because the Aged on recall is the area with only thick filaments as the thin filaments slide over there's no but H stones gonna get smaller what happens to the width of the I band it again gets narrower because that is the area that has only the thin filaments see they're sliding over so there's not going to be as much of that but then the last question says what happens to the width of the Iban I'm sorry what happens to the width of the a band well there's no change in that the a band is the length of the thick filaments there was already an overlap of the thin filaments on it so nothing really changes in that particular side because that band is going to be a combination of thick and thin filaments anyways so if you look at this picture over here you see a muscle where it's relaxed it's partially contracted and it's moving in and then it's completely contracted you can see how the H stone is going to be smaller as or more narrow as well as the I bands so let's look at components of a motor unit how does the nervous system talk to these muscle fibers well we're going to use a somatic motor neuron this is going to generate an action potential to stimulate the skeletal muscles or fibers to contract it's going to use a axon terminal this is the end of the axon that branches and it comes into close proximity to the muscle fiber which you can see here this is the axon terminal terminal means the end we then have a motor in plate this motor endplate is an area of the sarcolemma or the muscle fiber where the axon terminal is the closest it still is a space they're not actually physically touching okay so this is called the motor in plate this is going to be where the neurotransmitter receptors are going to be located and you can see a picture of it here with the axon terminal with the motor in plate on the muscle the gap that's between the axon and the sarcolemma or that motor in plate is known as the synaptic cleft this cleft is going to be where the neurotransmitters are going to then go to the receptors on the motor in plate the area that releases the neurotransmitters and the example of this is a Sidel choline this is going to be what we call the synaptic bulbs so they are going to be the ones who actually release the neurotransmitter this signal to the muscle the neuromuscular Junction is the synapses between the motor neuron and the motor in play of the muscle so when we talk about that synaptic cleft that area is also known as the Junction now collectively a single motor neurone Nura neuron and all the muscle fibers it stimulates is called a motor unit so the sub whole thing as a whole is known as a motor unit so again you can see in the picture you have the synaptic cleft you have the synaptic in bulb and then the area where the synaptic cleft is located is known as the neuromuscular Junction the whole motor neuron contains the neuron talking to the different skeletal muscle fibers all right so let's look at this contraction and how again this whole thing works looking at it with the actual neuron as well so for a contraction to take place a nerve impulse has to send an action potential and it has to reach the axon terminal which you can see up here on the number one the neurotransmitter acetylcholine is going to be released into the neuromuscular Junction into that synaptic cleft it's going to then diffuse across the cleft and it's going to connect or bind to the receptors for a Sydal choline on the sarcolemma the plasma membrane of the muscle cell when this happens it's going to trigger the release of calcium from the sarcoplasmic reticulum this is going to cause the calcium to go into the sarcoplasm and it's going to help start the contraction process the myosin heads will then attach to the actin filaments and pull on the actin filaments causing them to slide inward with that power stroke oh guys they can't do this unless calcium binds and releases the binding sites on the actin okay so this is why the calcium is so important it's got to bind to that trow Finan and tropomyosin so that the binding sites can be present so that those heads can connect and pull and do their power stroke this causes the sarcomere to shorten okay it causes that sliding to take place now this means that a contraction is going to require a number of things for one it's going to require this ATP and this calcium but this calcium and ATP is not even going to come in contact with those fibers unless it gets the message from the nerve through a Siddal choline so acetylcholine sooner that starts this whole process but calcium and ATP must also be present in order for a contraction to take place now for relaxation we need to see that the acetylcholine needs to go away so there's an enzyme called the acetylcholine race that's gonna inactivate the acetylcholine it's gonna break it apart this is going to make the calcium be transferred back into the sarcoplasmic reticulum all right so it's gonna suck it back up this is going to cause the actin filaments to slip back into the relaxed position because that troponin and tropomyosin cover the binding sites and the myosin heads can attach so they're going to slide back into their original position and relax in that process now relaxation guys is still going to require a couple of things it's gonna require the enzyme that's going to break down acetylcholine and it also requires ATP so guys energy is required to contract the muscle but energy is also required to relax the muscle we need the energy on both sides alright so in your PowerPoint here you can clip on you can click on this little clip and you can watch this little video that explains the muscle contraction with an animation alright so rigor mortis guys is what happens after death we see that at death the calcium starts to leak out of the sarcoplasmic reticulum this allows the myosin heads to attach to the actin filaments as long as ATP is present when no more ATP is being produced the muscle is going to not be able to relax because remember ATP is required to contract it but also to relax it so this is why the muscles go stiff and it lasts for about 24 hours until the actual muscle tissue starts to break down it starts to disinter 8 okay and so when we look at this we see that the contractions stay and that's why they can go in and if the individual is in rigor we know that they have been dead less than 24 hours because those muscle tissues haven't started to break down all right so let's talk about muscle metabolism okay so muscles are going to require a huge amount of chemical reactions to take place specifically in the formation of ATP so the generation of ATP and the muscle is going to use what we call a creatine phosphate this creatine phosphate such molecule that has a lot of stored energy it's only associated with our muscles and this creatine phosphate and ATP store enough in chemical energy to last for about 15 seconds now excess ATP is used to generate the CP this is done through kinase transfers of phosphate groups now remember kinase is an enzyme and you know this because it ends in ace so what happens here is ATP is gonna be broken down into adp and phosphate a kinase is gonna transfer that phosphate to of the creatine and this is what's going to create the creatine phosphate or this CP this is going to allow it to hold on to the phosphate molecule so it does not get lost and it can be transferred back to adp to generate more ATP when needed so this is a reversible reaction so creatine kinase or CPK or CKD is an enzyme associated with heart skeletal muscles in the brain elevated blood levels of CPK indicate that one of these organs have been damaged so it should not be in your blood but if it's showing up in your blood work then one of these has been damaged the heart skeletal muscles or brain so generation of ATP molecules are going to go through the process of aerobic respiration and of course it starts with glycolysis now glycolysis guys remember is an anaerobic process because oxygen is not required this is going to generate two ATP for each molecule of glucose that the muscle fiber takes in this allows for quick bursts of energy but it's only for a very short time because of the fact that it only makes two ATP glycogen is a complex carbohydrate which is our intermediate energy storage molecule that we do in muscles so when the muscles have the ability to store up some extra glucose they are going to store it in the form of glycogen now if no oxygen is present lactic acid is generated through this process of glycolysis because the pyruvic acid that's created at the inner glow' casas does not have the ability to go into the mitochondria if oxygen is absent so this process still continues but a waste product of lactic acid starts to build up this lactic acid is toxic to our muscles and this is what makes our muscles sore so if your muscles are sore after a ow that's telling you that you did not give your muscles enough oxygen we need to work on our breathing through those exercises we need our muscles to go into the ana or from the anaerobic stage to the aerobic stage of cellular respiration this is going to generate a lot more ATP from that glucose molecule it's going to generate about 36 ATP this does include the process of glycolysis because the pyruvic acid that's made in the glycolysis reaction is going to be used for the rest of this aerobic respiration oxygen is required to complete this breakdown of glucose into co2 and water remember that this does occur in the mitochondria the specialized organelle that we call the powerhouse so glycogen and our muscles is going to get broken back down into glucose this glucose is going to go through the process of glycolysis which occurs in the sarcoplasm this is going to create pyruvate pyruvate then needs to go into the mitochondria but in order to gain access it must have oxygen oxygens like it's ticket to get into the mitochondria so oxygen has to be present if oxygen is present then we can see another set of 36 ATP can be made and this is going to then create the byproducts of co2 and h2o and not the lactic acid we saw before in the anaerobic side no o2 is available so there's only two ATP that is formed and lacking lactic acid starts to build up this causes your muscles to fatigue and be sore your liver has the ability to take that lactic acid and return it or convert it back to pyruvate so your cells can use it but it has to get into the bloodstream this is one reason why we talked about how if you're sore you need to go ahead and work out your muscles because that working out process is going to push that lactic acid into your bloodstream which then can take it to the liver and not just sit in your muscle tissue making you even sore the next day if if that does occur so this was going to be what we would look at is oxygen recovery now guys in general oxygen depletion occurs when oxygen is not being supplied fast enough to your muscles during especially strenuous exercise a type of anaerobic respiration does Curren lactic acid builds up but during recovery elevated oxygen uptake does occur and oxygens used to convert some of the lactic acid back to pyruvate to go through the aerobic cellular respiration cycle in the mitochondria this allows for the generation the g2 allows the mitochondria to generate more ATP's now causes of muscle fatigue which is the inability to maintain strength of a contraction is going to be due to lowered calcium levels in the sarcoplasm okay so the muscles could be fatigued because they have low levels of calcium we also see there could be depletion of that creatine phosphate the glycogen or even ATP insufficient oxygen can also cause the muscle to fatigue a buildup of lactic acid which decreases the pH and your muscles which makes them not be able to work as efficiently decreases Sydal choline being released from your nerves because remember this whole process starts with the nerves sending the signal through the neurotransmitter acetylcholine if that's not being released properly the muscles are gonna start to get fatigued or weaker so let's talk about the control of muscle tension we see that the same-sized action potential or nerve impulse is used each time to stimulate the muscle fiber so as if you look at the bottom of the chart in blue you see that the motor neuron is sending the same signal it's there's no difference or deviation from it okay it's the same height the only thing that's different is how fast it's coming okay how many times it sends the signal the amount of muscle contraction or force of the muscle contraction does vary because so if you look here in the first one there's a certain amount of force but then the next one it kind of is moving up and so on okay so the muscle contraction force can change the force of contraction depends on the frequency of the muscle fiber stimulation okay so this is the rate of the nerve impulses not the actual height of it okay so we see that the height K is going to be the same but how quickly it's being sent changes how the muscle is going to have its contraction so guys a brief contraction of all muscle fibers in a motor unit due to a single action potential is known as a single twitch which we see here at the beginning of the chart we had one signal action potential and we had one single twitch however we do see that when when the stimuli is arriving at different times causing longer contractions this is called a wave summation so we look here it goes in two waves and we're adding it's getting bigger in the process a sustained contraction however it's still wavering in the process is known as an unfused tetanus hey because it's still building but it's not going to be a constant it's wavering but it's the same contraction is going to be a fused tetanus which you see here at the end and if you'll notice the frequency of the signals from the nerves are very close together they're sending it over and over and over again causing that summation to take place but it's fused it's a constant incline for that contraction so guys all muscle fibers of a motor unit will contract and relax together so the total tension produced by your during your muscle contractions depends on those number of fibers so one motor you neuron can contract multiple muscle fibers and on average it's about a hundred and fifty muscle fibers but in the eye we see that one motor neuron only stimulates ten fibers so it's a quicker movement that can take place but in the leg for those larger gross movements like for your quad one motor neuron is gonna stimulate 2,000 muscle fibers okay so it's a lot more that they have to get wrangled and working together versus the eye that only has to worry about ten all right so the difference there is how quick they can get them organize and get them moving and it's still relatively fast but the eye movements gonna be a lot quicker than the leg movements all right so let's look at what a twitch contraction is composed of we see first that there's this latent period this is between the stimulus or when an action potential was sent and the actual start of the contraction because we had to send the signal and we have to start letting those calcium ions rush out in order for it to start to contract this is known as the latent period so calcium is being released into the sarcoplasm from the sarcoplasmic reticulum the myosin heads are gonna start the process of attaching to the actin filaments they're getting ready they haven't done their power stroke yet but they're getting ready the contraction period is when the shortening of the sarcomeres does occur this is when the power strokes of the myosin heads is going to happen so calcium allows the myosin heads to attach to the actin because they add they are going to combine to that troponin tropomyosin this results in the power stroke of the myosin heads shorting the sarcomere but remember this does require ATP the relaxation period is going to be where the calcium is being pumped back into the sarcoplasmic reticulum this is when the myosin heads are going to detach and the lengthening of the sarcomere takes place remember the detachment of the myosin heads also requires the use of ATP now there is a relative refractory period that takes place this is the time the muscle and the nerve cells can actually not respond to the next stimuli this is a temporary loss of excitability and the muscle responds to the first stimulus but not the second refractory periods are gonna vary but depending on the type of muscle okay based on which type of muscle we're looking at now there's three types of muscle contractions there's isometric concentric and eccentric there's a video here that talks about the difference the difference is here but you need to watch the video and look at how we why we do certain workouts why some workouts are going to be where you have to sustain the movement you're holding it in place okay keeping that muscle engaged or are you going to be using the muscle back and forth in a movement all right this is just to give you an idea