14 (9) Muscular System Review Guide PDF

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Mark Wireman...

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Name: Rubie Rowe

Section: T/Th – 900A

Directions: You will learn best if you WRITE OUT THE QUESTIONS AND ANSWERS ON SEPARATE SHEETS OF PAPER!!! 1. List AND describe the functions of skeletal muscles.  Movement  Posture  Supports soft tissue  Guards entrances and exits  Provides heat/maintains body temperature  Storage of minerals 2. List AND describe the characteristics of skeletal muscle.  Responsiveness (excitability): to chemical signals, stretch and electrical changes across the plasma membrane  Conductivity: local electrical change triggers a wave of excitation that travels along the muscle fiber  Contractility: shortens when stimulated  Extensibility: capable of being stretched  Elasticity: returns to its original resting length after being stretched 3. What are two other names for a muscle fiber?  Muscle Fiber = myofiber = myocyte 4. Describe the number and location of nuclei in a myofiber.  Multinucleated  Cytoplasm 5. Muscle cells are packed full of which type of protein filament?  Myofibrils 6. Make sure you understand the difference between a myofiber and a myofibril!  Myofiber: a single muscle cell  Myofibril: bundles of protein filaments (actin and myosin) that causes contraction 7. What is another name for the muscle cytoplasm?  Sarcoplasm: contains glycogen and mitochondria to provide energy for contraction and myoglobin for binding oxygen 8. What is another name for the plasma membrane of a myofiber?  Sarcolemma 9. Describe the location of the T tubules, sarcoplasmic reticulum, and terminal cisternae. What is the function of each of these structures?  T tubules: circles around myofibrils, transmits signal to contract  Sarcoplasmic Reticulum: network around each myofibril  Terminal Cisternae: dilated end sacs, store calcium 10. What is a “triad” referring to?  Triad = 1 T tubule and 2 terminal cisternae 11. Label the connective tissue wrappings of a skeletal muscle.  Epimysium: surrounds ALL fascicles o Exterior collagen layer o Connected to deep fascia o Separates muscle from surrounding tissues  Perimysium: around A fascicle o Contains blood vessel and nerve supply to fascicles  Endomysium: around INDIVIDUAL muscle fibers

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o Contains capillaries and nerve fibers contacting muscle cells o Contains satellite cells (stem cells) that repair damage What is an aponeurosis? Where are some regions in the human body might you find one? How does an aponeurosis differ from a tendon?  Aponeurosis: sheet-like structure o Foot, shoulder, jaw  Tendon: cord-like structure What is the name given to the contractile unit of muscle?  Sarcomere What protein is the thin filament made of?  Thin Filaments = actin filaments o Composed of the protein myosin What protein is the thick filament made of?  Thick Filaments = myosin filaments o Composed of the protein myosin What exactly is a cross bridge?  Cross Bridge: myosin filaments that have heads (extensions) What is the function of a Titin protein? What two regions of the sarcomere does it connect?  Titin: responsible for passive electricity of the muscles o Connects at the Z-line and M-line of the muscle fiber Label the following regions of a sarcomere: a. Z – Line: thin filaments extended in each direction, middle of light band b. I –Band: light bands c. A – Band: dark bands d. H – Zone: portion of the A-band where the thick and thin filaments do not overlap e. M – Line: the middle of the dark band f. Thin filament: consists of a protein called actin g. Thick filament: consists of a protein called myosin h. Dark Band: A-line i. Light Band: I-line Which band of a sarcomere contains only actin?  I-band Which band of a sarcomere has actin and myosin?  A-band Which zone of a sarcomere has only “bare” myosin?  H-zone Which region of a myosin molecule attaches to actin? (Hint: it looks like a golf club head).  Head/cross bridge Describe AND draw the relationship between the following proteins in a sarcomere during muscle contraction AND muscle relaxation: a. Actin b. Myosin c. Myosin binding site d. Myosin head e. Troponin f. Tropomyosin g. Calcium (Ca) h. ATP and ADP What happens to the sizes of the following bands/regions of sarcomere during contraction AND relaxation? a. Distance between Z – Lines: shortens during contraction, lengthens during relaxation b. Size of I – Band: decreases during contraction, increases during relaxation c. Size of A – Band: no change during contraction or relaxation

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d. Size of H – Zone: decreases during contraction, increases during relaxation e. Length of individual actin and myosin filaments: shortens during contraction, lengthens during relaxation Explain, in detail, the concept of a motor unit. How would the arrangement of a motor unit differ for fine control vs. strength control?  A motor neuron and the muscle fibers (myocytes) it innervates o Dispersed throughout the muscle o When contract together causes weak contraction over wide area o Provides ability to sustain long-term contraction as motor units take turns resting (postural control)  Fine control – o Small motor units contain as few as 20 muscle fibers per motor neuron o Ie. Eye muscles  Strength control – o Larger motor units for power moves o Ie. Gastrocnemius muscle has 1000 fibers per motor neuron Describe, in detail, all of the components of a neuromuscular junction (NMJ) including: a. Synaptic knob: the swollen end of the nerve fiber b. Junctional folds: located on the sarcolemma, increase surface area of Ach receptors and contains acetylcholinesterase to break down Ach and relax muscles c. Synaptic cleft: tiny gap between nerve and muscle cell; is a space for reactions to occur d. Acetylcholine: chemical component released from neuron to produce a stimulus e. Acetylcholine receptors: sense the Ach being released into the synaptic gap and open channels to allow chemicals in for the muscle to contract f. Acetylcholinesterase: breaks down the Ach causing the muscle to relax Briefly summarize the four actions necessary for muscle contraction and relaxation.  Excitation: nerve action potentials lead to formation of action potentials in a muscle fiber  Excitation-Contraction Coupling: action potentials on the sarcolemma activate myofilaments  Contraction: shortening of muscle fiber  Relaxation: return to resting length Diagram AND explain in words ALL of the steps involved in muscle contraction AND relaxation. Yes, this will take you some time. You should know by now how you learn best, so choose a method that works for you. The more times you go through this and the more detail you include, the better off you will be!   Step 1: a nerve impulse travels down an axon and causes the release of acetylcholine  Step 2: acetylcholine causes the impulse to spread across the surface of the sarcolemma  Step 3: the nerve impulse enters the T tubules and sarcoplasmic reticulum, stimulating the release of calcium ions  Step 4: calcium ions combine with troponin, shifting troponin and exposing the myosin binding sites on the actin  Step 5: ATP breaks down ADP+P. The released energy activates the myosin cross bridges and results in the sliding of thin actin myofilaments past the thick myosin filaments  Step 6: the sliding of the myofilaments draws the Z-lines towards each other, the sarcomere shortens, the muscle fibers contract and therefore muscle contracts  Step 7: Ach is inactivated by acetylcholinesterase, inhibiting the nerve impulse conduction across the sarcolemma  Step 8: nerve impulse is inhibited, calcium ions are actively transported back into the sarcoplasmic reticulum, using the energy from the earlier ATP breakdown

Step 9: the low calcium concentration causes the myosin cross bridges to separate from the thin actin myofilaments and the actin myofilaments return to their relaxed position  Step 10: sarcomeres return to their resting lengths, muscle fibers relax and the muscle relaxes Explain, in detail, why an individual becomes rigid soon after death, but then days later, becomes floppy. Make sure to include the roles of ATP and calcium in your explanation.  Muscle cells have a massive release of Ca2+ from sarcolemma causing muscles to contract and stiffen, muscles become floppy again because there is no more ATP being produced to reset the sarcolemma and proteins start breaking down. Sketch the length tension curve and use it to describe the optimum length for a forceful muscle contraction. Make sure to explain what arrangement of actin and myosin is responsible for a forceful muscle contraction.  Amount of tension generated depends on length of muscle before it was stimulated Explain the phenomenon of “all or none” when describing muscle contraction.  In a muscle fiber, in order for contraction, all of the muscle fibers must be stimulated or no contraction will take place o All muscle fibers don’t fire at once, one goes, then another and another and so on till all fibers are contracting What does recruitment mean in terms of muscle contraction?  Stimulating the whole nerve with higher and higher voltage produces stronger contractions Draw AND describe what twitch would look like on graph.  One single curve, rather than multiple curves then lowers What are the three phases of twitch AND what is happening on the molecular and cellular level during each of these phases?  Latent period before contraction: o The action potential moves through sarcolemma causing Ca2+ release  Contraction phase: o Calcium ions bond o Tension builds to peak  Relaxation phase: o Ca2+ levels fall o Active sites are covered o Tension falls to resting levels Compare and contrast unfused and fused tetanus. Make sure to mention “treppe” in your answer.  Unfused: incomplete (bumpy) o Some relaxation occurs between contractions o Sustained, fluttering contractions of motor units o The results are summed into a smooth contraction  Fused: complete (smooth) o No evidence of relaxation before the following contractions o The result is an intense, sustained muscle contraction o Calcium is never reclaimed by the sarcoplasmic reticulum Compare and contrast isotonic and isometric muscle contraction. Give some examples of each.  Isotonic Muscle Contraction: o Same tension while shortening = concentric o Same tension with lengthening = eccentric  Isometric Muscle Contraction: o Develops tension without changing length 

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Important in postural muscle function and antagonistic muscle joint stabilization What is the difference between a concentric and eccentric isotonic contraction?  Concentric Contraction: tension exceeds resistance and muscle shortens  Eccentric Contraction: resistance exceeds tension and muscle lengthens (gravity) Explain what is meant by the statement that, “A muscle is never entirely relaxed.” Yes, this question is asking you to talk about muscle tone.  Some fibers are contracted even in a relaxed state Review the processes of anaerobic and aerobic respiration.  Anaerobic Respiration: no oxygen required, produces lactic acid, little ATP produced  Aerobic Respiration: oxygen required, produces H20 and CO2, more ATP produced Compare and contrast, in detail, what is occurring on a molecular and cellular level for immediate, short term, and long term energy needs of a muscle.  Immediate Energy Needs: o Short, intense exercise (100 m dash)  Oxygen need is supplied by myoglobin o Phosphagen system  Myokinase transferes Pi groups from one ADP to another forming ATP  Creatine kinase transfers Pi groups from creatine phosphate to make ATP o Result is power enough for 10 seconds of maximal exercise  Short-Term Energy Needs: o Glycogen-lactic acid (anaerobic) system takes over  Produces ATP for 30-40 seconds of maximum activity  Playing basketball or running around baseball diamonds  Muscle obtain glucose from blood and stored glycogen  Long-Term Energy Needs: o Aerobic respiration needed for prolonged exercise  Produces 36 ATPs/glucose molecule o After 40 seconds of exercise, respiratory and cardiovascular systems must deliver enough oxygen for aerobic respiration  Oxygen consumption rate increases for first 3-4 minutes and then levels off to a steady state o Limits are set by depletion of glycogen and blood glucose, loss of fluid and electrolytes What is creatine phosphate in terms of a supplement? Specifically, who is it going to benefit? Why?  Creatine Phosphate: a molecule that produces more ATP, the more energy produced, the more work a muscle fiber can do Describe on a molecular and cellular level what is occurring when a muscle becomes fatigued.  ATP synthesis declines as glycogen is consumed  Sodium-potassium pumps fail to maintain membrane potential and excitability  Lactic acid inhibits enzyme function  Accumulation of extracellular K+ hyperpolarizes the cell  Motor nerve fibers use up their acetylcholine What types of things would an endurance athlete be concerned with? Explain!  Oxygen uptake, for aerobic respiration, and nutrient availability for energy production and electrolyte balance to prevent muscle fatigue Describe what is occurring when a muscle goes into “oxygen debt.” Make sure to explain EPOC in your response.  Heavy breathing after strenuous exercise o

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o Known as excess post-exercise oxygen consumption (EPOC) Purposes for extra oxygen: o Replace oxygen reserves (myoglobin, blood hemoglobin, in air in the lungs and dissolved in plasma) o Replenishing the phosphagen system o Reconverting lactic acid to glucose (oxidation) in kidneys and liver o Serving the elevated metabolic rate that occurs as long as the body temperature remains elevated by exercise Compare and contrast slow twitch and fast twitch muscle fibers.  Slow Twitch Fibers: o Slow oxidative fibers  Smaller diameter, more mitochondria, myoglobin and capillaries  Adapted for aerobic respiration and resistance to fatigue  Slow to contract  Soleus and postural muscles of the back  Fast Twitch Fibers: o Have large diameter, few mitochondria, large glycogen reserves o Fast glycolytic, fast-twitch fibers  Rich in enzymes for phosphagen and glycogen-lactic acid systems  Sarcoplasmic reticulum releases calcium quickly so contractions are quicker  Extraocular eye muscles, gastrocnemius and biceps brachii o Fatigue quickly How exactly do strength workouts increase muscle size?  Stimulates cell enlargement due to synthesis of more myofilaments  Hypertrophy (increased muscle size) vs. increase in the number of muscle cells What is DOMS? What exactly causes it?  Delayed Onset Muscle Soreness: caused by a buildup of lactic acid in the muscle tissue from strenuous activity What affect does endurance training have?  Produces an increase in mitochondria, myoglobin, glycogen, and density of capillaries – less lactic acid production Compare and contrast skeletal muscle, cardiac muscle, and smooth muscle making sure to include the following in your comparison. This question may be more appropriate for the lab portion of this course: a. Does it have one nucleus or is it multinucleated? b. What is the location of nucleus (central vs. peripheral)? c. Striated or non-striated? d. Voluntary or involuntary? e. Can it divide? f. Intercalated discs? g. Major function? h. Where in the human body is it found?  Skeletal Muscle: o Multinucleated o Peripheral o Striated o Voluntary o Can divide o Intercalated discs o Function: movement o Attached to bones  Cardiac Muscle: 

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o One nucleus o Central o Striated o Involuntary o Can’t divide o No intercalated discs o Function: pump blood o Only found in the heart Smooth Muscle: o One nucleus o Central o Non-striated o Involuntary o Can divide o Intercalated discs o Function: contraction of internal organs o Walls of blood vessels, visceral organs

50. When smooth muscle contracts in blood vessels, what happens to the size of the lumen? What happens to blood pressure at that area?...