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Muscular System Slide 2 Types of Muscle Skeletal striated & voluntary Smooth involuntary Cardiac - heart The word striated means striped. Skeletal muscle appears striped under a microscope. Slide 3 Role of Muscles in the Body Slide 6.8 Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings Produce movement Maintain posture Stabilize joints Generate heat Propel Substances Slide 4 Muscles and Muscle Fiber Structure Muscles are composed of many fibers that are arranged in bundles called FASCICLES Individual muscles are separated by FASCIA, which also forms tendons Video on plantar fasciitis. Slide 5 EPIMYSIUM = outermost layer, surrounds entire muscle. PERIMYSIUM = separates and surrounds fascicles (bundles of muscle fibers) ENDOMYSIUM = surrounds each individual muscle fiber This model of the muscles uses straws to represent fibers. Green = endomysium Yellow = perimysium Blue = epimysium Slide 6 Muscle Layers Slide 7 Epimysium Perimysium Endomysium Slide 8 Sarcolemma = muscle fiber membrane Sarcoplasm = inner material surrounding fibers (like cytoplasm) Myofibrils = individual muscle fibers, made of myofilaments Muscles / Cells Slide 9 Sarcolemma Mitochondrion Sarcoplasm Myofibril Nucleus Slide 10 Myofibrils are made of ACTIN = thin filaments MYOSIN = thick filaments Slide 11 Myofilaments ACTIN (thin) and MYOSIN (thick) -- form dark and light bands A band = dArk thick (myosin) I band = lIght thIn (actin) Slide 12 Slide 13 Slide 14 Slide 15 It is important to remember the hierarchy fasicles myofibrils myofilaments actinmyosin Slide 16 Muscle Contraction A skeletal muscles contraction begins at the neuromuscular junction. What do you think the definition of neuromuscular junction would be? Slide 17 How Muscles Work with the Nervous System NEUROMUSCULAR JUNCTION - where a nerve and muscle fiber come together Slide 18 1. Neuron 2. Sarcolemma (or motor end plate) 3. Vesicle 4. Synapse 5. Mitochondria Motor Unit or Neuromuscular Junction Slide 19 Neuromuscular Junction Slide 20 The neurotransmitter that crosses the gap is ACETYLCHOLINE. This is what activates the muscle. Acetylcholine is stored in vesicles Slide 21 Slide 22 Neuromuscular junction animation animation Focus Questions: What is the name of the stimulus that travels down the axon to the muscle fiber? An action potential Does the terminal (end) of the axon enter the muscle fiber? No. There is a gap between the two. Does acetylcholine enter the muscle fiber? No. What chemical does enter the muscle fiber, resulting in an action potential through the muscle fiber? Sodium Slide 23 SLIDING FILAMENT THEORY (MODEL) The theory of how muscle contracts is the sliding filament theory. The contraction of a muscle occurs as the thin filament slide past the thick filaments. The sliding filament theory involves five different molecules and calcium ions. The five molecules are: myosin actin tropomyosin troponin ATP Slide 24 Slide 25 Slide 26 ANIMATION OF SLIDING FILAMENT http://bigpictureeducation.com/animation-sliding-filament-theory Slide 27 Sliding Filament theory Boat = Myosin (thick filament) Oar = Myosin side arm Water = Actin (thin filament) Life ring = Calcium Slide 28 Resting 1.ATP is bound to myosin side arm. 2.ATP cleaves into ADP + P (high energy) Slide 29 Step 1 Action potential 1.A nerve action potential releases acetylcholine into the synaptic cleft opening the Na+ channels. 2.Action potential spreads across sarcolemma releasing Ca into sarcoplasma Slide 30 Step 2 Myosin-actin binding 1.Ca binds to troponin. 2.A shape change in troponin moves tropomyocin out of the way of actin binding site. 3.Actin and myosin bind using energy from cleaved ATP. Slide 31 Step 3 Power Stroke 1.Side arm pivots so myosin and actin slide by each other shortening the sarcomere. 2.ADP and P released (low energy) Slide 32 Step 4 ATP Binding Actin-myosin release 1.A different ATP molecule binds to active site. 2.Actin released Slide 33 Step 5 ATP cleavage 1.Return to high energy state 2.Cycle will repeat if Ca still available. Slide 34 Think it over The boat (myosin) does not move far in one cycle, can a muscle contraction occur with one cycle? No If a muscle is contracted what happens if a new molecule of ATP is not available? Muscle stays contracted- cramps Why does rigor mortis occur? (Hint: What chemical is no longer available to the body?) ATP is not available to control Ca release so contractions are continuous 6-8 hours after death. Body relaxes 16-24 hours as enzymes break down contractile structures. Slide 35 Sarcomere summary Slide 36 Sliding Filament Theory Focus questions: What happens to the length of the sarcomere during a contraction? The sarcomere shortens. Slide 37 Sliding Filament Animation animation 2 Focus Questions: What chemical exposes the binding site for actin and myosin? Ca What is the source of energy for a contraction? ATP What is the name of the step in which the actin filament is actively contracted? Powerstroke What chemical must be present in order for the actin and myosin filaments to separate? ATP Slide 38 Muscle contraction at the macroscopic level 1.Place your fingers along the angle of your jaw just in front of your ear. Grit your teeth and fell what happens to the hardness of the masseter muscle. During muscle contraction the muscle becomes ________________________. Slide 39 2.With your thumb and little finger of one hand, span the opposite arms biceps from the elbow to as close to the shoulder as possible. Bend the arm and observe the change in the length of the muscle. During muscle contraction the muscle ___________________ in length. Slide 40 3.Wrap a string around your extended upper arm and determine the circumference. Clench your fist tightly and flex your arm to contract the muscle. During muscle contraction the diameter of the muscle _____________________. Slide 41 Energy Source -ATP is produced by CELLULAR RESPIRATION which occurs in the mitochondria -Creatine phosphate increases regeneration of ATP * Only 25% of energy produced during cellular respiration is used in metabolic processes - the rest is in the form of HEAT. -maintains body temperature. Slide 42 Why might products like pro-creatine claim to increase energy? ATP = adenosine triphosphate ADP = adenosine diphosphate Slide 43 Other Terms 1. Threshold Stimulus 2. All-or-None Response 3. Motor Unit 5. Recruitment 6. Muscle Tone 7. Muscular Hypertrophy 8. Muscular Atrophy 9. Muscle Fatigue 10. Muscle Cramp 11. Oxygen Debt Slide 44 1. Threshold Stimulus Minimal strength required to cause a contraction Motor neuron releases enough acetylcholine to reach threshold 2. All-or-None Response Fibers do not contract partially, they either do or don't Slide 45 3. Motor Unit The muscle fiber + the motor neuron 4. Recruitment more and more fibers contract as the intensity of the stimulus increases 5. Muscle Tone Sustained contraction of individual fibers, even when muscle is at rest Slide 46 6. Hypertrophy - muscles enlarge (working out or certain disorders) 7. Atrophy - muscles become small and weak due to disuse Slide 47 8. Muscle Fatigue - muscle loses ability to contract after prolonged exercise or strain 9. Muscle Cramp - a sustained involuntary contraction 10. Oxygen Debt - oxygen is used to create ATP, -- not have enough oxygen causes Lactic Acid to accumulate in the muscles Soreness *See Magic School Bus Slide 48 11. Origin and Insertion Origin = the immovable end of the muscle Insertion = the movable end of the muscle The biceps brachii has two origins (or two heads). Slide 49 What is rigor mortis? A few hours after a person or animal dies, the joints of the body stiffen and become locked in place. This stiffening is called rigor mortis. Depending on temperature and other conditions, rigor mortis lasts approximately 72 hours. The phenomenon is caused by the skeletal muscles partially contracting. The muscles are unable to relax, so the joints become fixed in place. Slide 50 What is tetanus? Tetanus causes cholinosterase to not break down the acetylcholine in the synapse. This results in a person's muscles contracting and not relaxing. A tetanus shot must be administered shortly after exposure to the bacteria. Once you develop tetanus, there is no cure.