Muscles. Eli Abidor Anton Pashyk

Transcription

1 1 Muscles Eli Abidor Anton Pashyk

2 2 TABLE OF CONTENTS Introduction: muscles and you 3 Types of muscles 4 Muscle structure 6 How muscles work 7 Keeping it all together: Tendons 10 Muscles in your body 11 Exercise 12 Energy use 13 Glucose 15 Nervous control 16 Injuries 18 Helping to heal the muscle 19 Strength 20 Glossary 21 Illustration credits 22 About the authors 23

3 3 MUSCLES AND YOU RIGHT NOW, your eyes are moving across this page, slowly moving from left to right, reading this book. Right now, you might be raising your hand so you can ask to go the bathroom. Right now, you might be chewing on your pencil at the same time your eyes are moving across the page. You might not think about it now, but all of these things are made possible through the incredible and complex system of muscles that are inside you right now, working together to let YOU do everything you want to do. Without muscles, Michael Phelps wouldn t have ever been able to propel himself through the water and to seven Olympic medals. Without muscles, Kobe Bryant wouldn t twist and dribble his way into being the best point guard in the NBA. And without muscles, you would probably have a pretty hard time trying to play any of your favorite sports. Come to think of it, you wouldn t be able to do anything that you wanted to at all. But as amazing as what muscles can do, what s even more amazing is how they do it. They are one of the most unique kinds of parts of the body, that turn the food you eat into the ability to do whatever you want to do.

4 4 Types of muscles There are three different kinds of muscles inside the body: Skeletal muscle These are the muscles we can control. From shaking someone s hand to throwing a baseball, these are the muscles that make it happen. They are called skeletal muscles because they join two different parts of the skeleton, so when the muscles contract they move one of the parts of the body. Smooth muscle These muscles are NOT voluntary! They will keep working whatever you do. This group includes muscles in the lining of organs. A good example is the esophagus (your throat); there, the muscles contract and relax in a wave motion to bring food to your stomach. Cardiac muscle These are the muscles that make up your heart. They are both like skeletal muscles, in the way they re built, and like smooth muscle, because they are involuntary. Skeletal and smooth muscle both are striated, meaning that they are organized in neat little bundles of muscles. Did you know? Goosebumps are actually caused when smooth muscles called arrectores pilorum contract and make your hairs stand up.

5 5 Types of muscles Besides the three main muscle types, all muscles can be divided into a few other categories Type I - Slow twitch This muscle is slow twitch or "red" muscle. It has a lot of really small blood vessels called capillaries, as well as a bunch of molecules called myoglobin which give it a red color. Most of the skeletal muscles are Type I, which is why most body diagrams show red muscle. It can carry more oxygen, which helps the muscle keep moving for longer. Type II - Fast twitch Type IIa: This muscle is also full of capillaries and myoglobin, giving it a red color Type IIx: This is the fastest muscle type in the whole body. It works in short, powerful bursts that release force very quickly. But because it's so quick, type IIb muscle groups can only stay contracted for short amounts of time Type IIb: This muscle has the least amount of myoglobin, which gives it to a whitish color. (If you go to page 8, you can see the muscle groups that are type IIb because they are white instead of red. Different people naturally have different amounts of fast and slow twitch muscle. Depending on which type of muscle you have more of, you might be a better sprinter, long distance runner, or weight lifter. Did you know? Some small rodents have only type IIb fast twitch muscle, which is what makes them look so pale (and maybe with all that fast twitch muscle it s the reason Tom never could catch Jerry)

6 6 Muscle structure: How muscles are made If you look at your arm when you flex, you can see that a pretty big part of your arm is made of muscle. Just like every other part of your body, your muscles are made of tissues and cells. Every muscle is made up of thousands of cells called muscle fibers. They are one of just a few types of cells that can grow to be really long. Each and every muscle fiber goes from one end of a muscle to the other. Bunches of muscle fibers are wrapped together by a membrane called the perimysium (pear-e-me-see-um) into little bundles called fascicles. These groups of muscle cells also have connective tissues called endomysium (endo-me-see-um) in between each cell. They help cushion the cells and have nerves and blood vessels in them. Groups of fascicles are wrapped together again by an even bigger perimysium into one muscle.

7 7 How muscles work Ever wonder what really makes you lift your legs so you can run to the bus in the morning after sleeping in late? Here s how it happens: The BIG picture: Contracting and Relaxing Your muscles can only do one thing: contract (which is just a fancy word for tighten or shrink). In other words, they get shorter and squish together; when you flex your arm, your biceps contract and get shorter, which pulls in your forearms (the farthest part of your arm). This is how any part of your body moves. Because each group of muscles can only make a part of you go one way, every part of you has another group of muscles that it make go the other way. Each muscle cell (fiber) can only contract for a split second, so they stop contracting just like that. After, they have to build up the energy to contract again. Now go ahead and raise your arm out to the side and wait a few seconds. Is it still there? Of course it is! So how can it stay up? The reason that your arm can stay up is because those muscles work in teams taking turns. Only some of the muscles contract at a time. This way, those split seconds add up so you can keep your arm, your leg, or any other part of you, moving. One more important thing to know is that even when you re resting, your muscles are always contracting at least a few of those muscle fibers. It s called having muscle tone; if you don t have any, then you d fall to the ground right where you stand (or slump over onto your desk).

8 8 The microscopic picture: how cells contract Of course the only reason that a muscle contracts is because the thousands and thousands of muscle cells can also contract. So how do they do it? Here s the overall idea: Each muscle fiber or cell has a whole bunch of myofibrils (my-oh-fib-rils). They re kind of like ropes and, just like the cells, they re as long as the entire muscle. Myofibrils are made of thousands of connector blocks called sarcomeres (sarrco-meers) Sarcomeres are made of two parts, actin and myosin. Two actin molecules are to the side of a myosin molecule

9 When a muscle contracts, you can pretend that two actin players play tug-of-war with a myosin rope. As they play, they grab, pull, and slide closer to each other. That way, each pair of actin players get closer. All that pulling and sliding together adds up, and the muscle fibers shrink, bringing the two parts of the body closer. 9

10 10 Keeping it all together: Tendons Want to know how your muscles stick with the rest of your body? Here are a few questions and answers to help you find out What are tendons? Because each of your muscles work hard every single day, moving the same two groups of bones over and over, they need something strong to connect them that will keep working just as hard. That's where tendons come in. What are they made of? Tendons are a tough fibery tissue that connects each muscle at both ends to a few different bones in the body. Because muscles stretch and move and twist with the body part its moving, so do the tendons that attach them to your bones. Because of that, tendons have to put up with a lot of wear and tear, so they are very elastic (stretchy) and strong. They are made of a protein called collagen. How are they Attached? Sometimes, tendons grow right into the bone; minerals build up around the tendons, acting like a really strong glue. In other parts of the body, the tendons combine with a membrane that surrounds the bone.

11 11 Muscles in your body Every single muscle in your body plays an important role in your day to day life. However, to get an idea of which muscles play which roles in moving the body, here are a few examples: Pectoralis major: these are your chest muscle. These pull your arms in toward your body Deltoid: These muscles over the shoulder bring the arms up, forward, and back. Rectus abdominis: these segmented muscle pull you re the front of your upper body closer to your legs Quadriceps femoris: These are the main muscles that extend and rotate your leg Latissimus dorsi: These are the back muscles that pull your arms back and down Gluteus maximus: Yup, these are the muscles in your rump! They help your hamstrings rotate your leg backward. Hamstrings: These muscles are the main muscles that flex and rotate the muscles backward. Gastrocnemius: Also called your calf muscles, these muscles help push your feet down when you are walking.

12 12 Exercise There are two types of exercises that are focused on two different muscle groups: Aerobic exercise Long time exercizes that require little force, such as running, are called aerobic. These exercizes require large amounts of protein, fat, and ogygen, while producing small amounts of lactic acid. Anaerobic exercise Short excercizes that require large amounts of force, such as weight lifting, are called anaerobic. These exercizes require large amounts of glucose (sugar) and produce large amounts of lactic acid. Note: Large concentrations of lactic acid in the muscle will cause the muscle to stop contracting. With more exercize, the body is able rid the muscle of lactic acid faster, allowing for longer periods of physical labor. If you are a really good athlete, your body will be able to transform lacid acid into enegy, which would mean more exercize time. Did you know? Some people are much better at aerobic exercises, while others are much better at anaerobic because everyone is born with a greater ability to grow that particular set of muscles. Those muscles become larger because every cell in your muscle grows after an exercise. Each cell can grow bigger and bigger without a limit until you will look like that guy <-

13 13 Energy use ATP Have you ever wondered why people get tired of physical work such as running? Why can't people just run forever? Well, the answer is in ATP. What is ATP? The proper scientific name for ATP is adenosine triphosphate. It is made by binding adenine nucleotide to three phosphates. Those bonds store a lot of energy. When those bonds are broken, the energy is released in a form of adenosine diphosphate (ADP) and a free phosphate group. Muscle cells than use that energy for rapid muscle contraction. Did you know? Even through your body has three different systems to make ATP, most of ATP is usually produced from only one at a time. A marathon runner, for example, would get his ATP energy from a different system than the sprinter would! How? Well, that is explained in the next page.

14 Where does ATP comes from? 14 Whenever a muscle has excess energy that it isnt using, that energy is converted back into ATP to be used later. Also your body has three different systems to make ATP. Phosphagen system The phosphate system can provide the energy for extreme rates of muscles use, such as sprinting, for about 10 seconds. This system is made up of ATP that is already in the muscles and in creatine phosphate which occurs in muscle cells. The ATP runs out after about 3 seconds. The body then converts creatine phosphate, which is found in the muscle cells, into ATP. Glycogen-lactic acid system Each cell in the muscle contains glucogen, which can be splited into glucose. That glucose is the converted into ATP and lactic acid. The body requires 12 steps to complete the conversion process; therefore, this process is much slower than the phosplhagen system. However, the glycogen-lactic acid system can provide energy for the muscle until too much lactic acid has built up, which takes about 90 seconds. Aerobic respiration After about two minutes of extreme muscle use, the body begins using oxygen in the glucose conversion process described above. This process is much slower that any other because it takes a while for the heart and lungs to provide it.

15 15 Glucose Glucose is a carbohydrate molecule that is broken down to release energy, which is stored in the form of ATP. In simplier words, glucose is sugar. Your body relies on these sugar molecules. Everytime you exercise for a long period of time, your body is using up the glucose stored in the muscle cells. Commercially, glucose can be obtained from starch. In America, cornstarch is used the most. Therefore, eating food that contains sugar is good for the body, BUT too much sugar can lead to diabetes. Did you know? Through aerobic respiration, described in the exercise section, one gram of glucose can produce 3.75 food calories. A pound can fuel you for most of the day!

16 16 Nervous control Ever wondered why your muscles move in the first place? Why do they do what you want them to do? Why don t muscles just go wild whenever they want? All this is controlled by your hard working brain. Efferent leg The efferent leg is a portion of your peripheral nervous system. Its main objective is to carry commands to and from the brain to your muscles. Each group of muscles has a dedicated region in the brain that will control the action of that group of muscles. Therefore, if a portion of your brain stops working, you will lose control over some of the muscles, but not all of them. Afferent leg This portion of the nervous system transports sensory information to and from the brain. This information can be something that you touch, temperature, moisture, and etc. This system is also responsible for your position awareness. It tells the brain where each of your muscles is and how it is positioned. To better understand this concept, follow the steps in the exercise on the next page.

17 17 Brain control activity! 1) Close your eyes and do not open them until this exercise is completed (note: you should read the rest of the boxes first in order to know what you are doing). 2) Lift up your hand and slowly wave it around. Notice how you still know where your hand is, even though you cannot see it. 3) Touch something. Can you tell what it is? How do you know that? (shape, temperature, etc.) As long as your nervous system is working properly, you will always know what you are touching and where all of your muscles are located. Nervous system diagram

18 18 Injuries Have you ever wondered why it hurts whenever something hits you? Your muscles are being injured! Contusion Contusion is a type of injury that you get when you get hit really hard. This can occur whenever you play a sport such a football. The pain is felt immediately and continues for a long period of time. Strains Strains occur whenever a muscle has been stretched more than it can handle. In that case a portion of the muscle, and sometimes the whole muscle, can tear. Immediate pain follows a muscle strain. Recovery from a serious sprain muscle sprain can require a surgery and 3 month of care; therefore, it should be taken very seriously. Cramps Muscle cramps occur when a muscle is compressed too tightly. This can happen after a sudden drop of temperature, like jumping into a cold pool, or simply by overworking a muscle. Did you know? Bruises are actually parts of the muscle that has experienced severe contusion Helping to heal the muscle and began to bleed. Because the bleeding is inside the muscle, we cannot see the blood. Instead we see the purple, and sometimes green, spots on our skin!

19 19 Aid your muscle The first thing you should do is protect the muscle from further injuries. Make sure the muscle is tightly wrapped to minimize muscle movement. An icepack should be aplied for periods of minutes to ease the pain. Make sure not to put any ice directly to the skin because that will cause frostbite, which leads to more problems. Also watch out for your diet. Eat a lot of protein to provide the the building material for muscle recovery. Until fully healed, the impaired muscle not undergo any physical activity. The damaged muscle should also be evelated above the heart level because that will minimize the blood flow to the muscle. This will relieve any pressure and easy the healing process.

20 20 Strength Have you ever wondered which muscle is actually the strongest? You might be surprised to find out that there are several! It all depends on your definition of "strong". Lifting If lifting things is your defenition of strong than the jaw is actually the strongest muscle in your body. The record force is 975 pounds of force that was produced for 2 seconds! That's enough force to squash a small car! Size If your definition is based on the size of the muscle, than the strongest muscle is actually the buttocks muscle called the gluteus maximus. The smallest outside muscle would be youe eyeball. Durability If durability of the muscle defines the strongest muscle, than the heart beats every other muscle. Over your lifetime it beats about 2.5 BILLION times. Did you know? Many people say that the tongue is the strongest muscle in the body; however, it is actually composed of 16 separate muscles!

21 Glossary Actin molecule that pulls and tugs to reduce the length of a sarcomere Cardiac muscle involuntary muscle found in the heart Endomysium substance within a fascicle in between muscle fibers Fasicle bundles group of muscle fibers Muscle Fiber muscle cell that stretches the length of the muscle Myofibril bundles of molecules that can decrease and increase in length Myosin protein molecule that is pulled and tugged on by actin Perimysium membrane surrounding a group of muscle fibers Tendons connective tissue between muscle and bone Tone constant state of partial contraction in a muscle Sarcomere smallest component of a myofibril that can still contract Skeletal muscle voluntary muscle that provides movement and locomotion Smooth muscle involuntary muscle that lines the organs 21

22 22 Illustration credits p. 3: p. 4: p. 5: p. 6: p. 7: p. 8: p. 9: p. 10: iverfunction_files/glucose.gif p. 11: p. 12: p. 13: p. 14: p. 15: pp. 16: pp. 17: pp. 18:

23 23 About the Authors Eli Abidor is a junior at Mass Academy. He has experience in co-authoring scientific textbooks as well as authoring and publishing a research paper. He hopes to go into the field of architecture or civil/environmental engineering. His hobbies include drawing, skiing, reading, music, and model-making. Anton Pashyk is a junior at Mass Academy. He has written several co-authored book chapter and research papers. His interests include computer programming, sports, and music. He hopes to go into the field of computer programming for a career.