CLASS SET Unit 4: The Muscular System STUDY GUIDE

Transcription

1 NPHS Anatomy & Physiology Questions to answer: 1) List three functions of the muscular system. 1) movement 2) thermogenesis (generates heat) 3) posture & body/joint support CLASS SET Unit 4: The Muscular System STUDY GUIDE 2) What are the four TWO characteristics of muscle tissue? Briefly explain them. 1) Excitability (irritability): ability to respond to certain stimuli by producing electrical signals called action potentials (Stimuli= neurotransmitters or hormones) 2) Contractility: ability to shorten & thicken 3) Distinguish between skeletal, smooth, and cardiac muscle. Include where in the body each type of muscle is found. Muscle Type # of nuclei Striated? Voluntary/ Function/where found MISC per cell involuntary? Smooth 1 invol Lines organs; surrounds breathing tubes Electrical impulse passed directly from cell to cell Cardiac 1 Invol Heart Electrical impulse passed directly from cell to cell Skeletal Many (multi) Yes vol Attached to bones Motor neuron electrical impulse passes to chemical message to start electrical in fiber 4) Differentiate between prime mover, synergist, antagonist and fixator. Prime mover: main muscle causing muscle movement antagonist: muscle(s) that works in opposition to prime mover 5) What is the antagonistic muscle group to the hamstrings? Quadriceps6) Distinguish between the origin and the insertion of a muscle. Origin: part of the muscle that is the attachment Insertion: part of the muscle that pulls on a bone; the insertion moves towards the origin 7) a) Label the following diagram. Bone: D Endomysium: B Tendon: F Muscle fiber: C Epimysium: A Fasicle: H Perimysium: E Fascia: G b) What is the relationship between a myofibril and a muscle fiber? Many myofibrils make up a muscle fiber. c) What are myofibrils made up of? myofilaments

2 Endomysium: surrounds each muscle cell within the fascicle (difficult to see in this diagram) Muscle fiber *Not shown: myofibril coming out of the muscle fiber 8) a) What is the role of the neuromuscular junction? Pass voluntary message from nervous system (motor neuron) to muscle fiber (cell) b) What two structures approach each other at the neuromuscular junction? Motor neuron and muscle fiber 9) a) What composes a motor unit? 1 motor neuron and all the muscle fibers it passes its message to b) Why would you engage a different number of motor units? To get different amounts of strength. The more motor units you engage, the more force behind the muscles contraction. c) How many motor units are in this diagram? 2; 1 red and1 blue 10) a) Draw & label the parts of a sarcomere. Thin filament: actin, tropomyosin, & troponin b) Why do skeletal muscles appear striated? Because it is lighter in color where there is just actin, darker in color where there is just myosin, and darkest in color where there is both actin & myosin

3 11) a) Where are calcium ions stored within the muscle? Sarcoplasmic Reticulum b) How is the release of calcium ions triggered? When an electrical impulse travels down the T- tubule, the gates of the sarcoplasmic reticulum open and calcium is released into the cytoplasm (sarcoplasm) of the cell. 12) What is the function or role of each of the following in a muscle contraction? Acetylcholine: chemical/neurotransmitter that is released from a motor neuron; it passes the message from a motor neuron to a muscle fiber Acetylcholinesterase: enzyme (~ase ending) that breaks down ACh in the synaptic cleft T-tubule: passes action potential through cell from sarcolemma (cell/plasma membrane) to sarcoplasmic reticulum Sarcoplasmic reticulum: stores calcium, releases calcium & pumps calcium back into the sarcoplasmic reticulum Calcium ions: stored in sarcoplasmic reticulum; binds to troponin & causes it to change shape Troponin: thin filament protein; small protein on tropomyosin that regulates whether tropomyosin blocks cross-bridge binding sites; changes shape when Calcium binds to it Tropomyosin: thin filament protein; long protein wrapped around actin which covers the cross bridge binding sites Actin: thin filament protein; cross bridge binding sites are here Myosin: thick filament protein; myosin head can change position from high energy to low energy position which pulls actin towards the center of the sarcomere; the head binds to actin Cross bridge binding site: spot on actin where the myosin head binds ATP: energy (made by mitochondria) used to break cross bridge & to provide energy for myosin to return to high energy position 13) Using a flow chart (xxx xxx xxx etc.), chart the steps of a muscle contraction. Be as detailed as possible and be sure to include the following terms/phrases: motor neuron, electrical impulse/action potential, vesicles, ACh, ACh receptors, new action potential/electrical impulse, sarcolemma, T-tubules, sarcoplasmic reticulum, Ca +2, troponin, tropomyosin, cross-bridge binding-sites, cross-bridge, actin, myosin head high energy position, myosin head low energy position, thin filament, center of sarcomere, ATP. 1. An electrical impulse (action potential) travels down a motor neuron and reaches the end. 2. When the electrical impulse/action potential reaches the end, this causes the vesicles containing ACh to empty into the synaptic cleft by exocytosis. 3. ACh neurotransmitter diffuses across this neuromuscular junction space and binds to ACh receptors embedded within the muscle fiber s plasma membrane (sarcolemma). 4. When ACh binds to these receptors, this causes a new action potential/electrical impulse in the muscle fiber. 5. The electrical impulse travels across the sarcolemma and then down the T-tubules which causes Ca +2 channels in the sarcoplasmic reticulum to open. 6. Ca +2 rushes out of the sarcoplasmic reticulum and binds to troponin.

4 7. When Ca +2 binds to troponin, this causes it to change shape. 8. The change in troponin s shape causes it to pull on tropomyosin exposing the myosin cross-bridge sites. 9. Each myosin head is already in its high energy position and immediately binds to the cross bridge site on actin forming a cross-bridge. 10. The energy in the myosin head is released and the myosin head falls down to its low energy position. 11. When myosin moves to its low energy position, it pulls on the actin filament (thin filament) and actin moves towards the center of the sarcomere. 12. ATP binds to the myosin head causing the cross bridge to break. 13. The energy from ATP is used to cause the myosin head to return to its high energy position. 14. As long as Calcium is present, another cross bridge will form and steps #9-13 will repeat. 14) What two events occur to end a muscle contraction? Acetylcholinesterase breaks down ACh insynaptic cleft Calcium pumped back into the sarcoplasmic reticulum (therefore troponin returns to original shape) Steps after #14 from previous question: 15. When the electrical message stops being sent down the motor neuron (because you want to stop the muscle contraction), Acetylcholinesterase will break down the ACh in the synaptic cleft. 16. Therefore, the electrical impulse no longer passes through the T-tubules and the Calcium gates in the sarcoplasmic reticulum close. 17. Calcium is pumped back into the sarcoplasmic reticulum. 18. Without calcium, troponin returns to its original shape which causes tropomyosin to cover up the cross bridge binding sites on actin. 19. The actin filaments slide back out and the muscle is relaxed. 15) a) How does a muscle get bigger as a result of working out? (What is increasing?) more myofibrils (so therefore more myofilaments) b) List 3 effects of aerobic (endurance) exercise. Increased # s of capillaries in and around muscles Increased # s of mitochondria More myoglobin 16) Differentiate between an isometric and an isotonic contraction and give an example of each. Isometric: same length but tension changes (holding posture; holding a weight; pushing on a door jam or wall) Isotonic: same tension but length changes (moving your arm; ex: extending arm/flexing arm) 17) a) Distinguish between a twitch and tetanus. twitch: 1 single impulse from motor neuron resulting in a twitch contraction tetanus: summation of twitches really close in time to cause a smooth, sustained contraction b) How does a muscle reach tetanus? Lots of individual twitches added together 18) What is tonus? Give an example. Partial contraction of some of your muscles; you sitting in your chair

5 19) What is this entire reaction called? Cellular respiration Glucose Pyruvate ATP + CO2 + H2O 20) a) What is the immediate source of energy for a muscle contraction? ATP b) What cellular organelle produces the molecule from question #20a? mitochondria 21) a) What is lactic acid? What pyruvate is converted into in skeletal muscle fibers when there isn t any oxygen for pyruvate to enter the mitochondria b) When does it accumulate in muscles and what is the result? Accumulates when there is a lack of oxygen; results in oxygen debt and burning sensation in muscle 22) What is the smallest stimulus strength that actually results in a contraction? Threshold stimulus 23) a) Distinguish between hemoglobin and myoglobin. Hemoglobin: protein in red blood cells that carries & then releases oxygen; myoglobin: protein that temporarily stores oxygen inside muscle fibers b) Distinguish between slow fibers and fast fibers. Slow: do not twitch as fast; for endurance; uses oxygen more efficiently; more mitochondria Fast: twitches faster; for immediate burst of speed or contraction; fatigues quickly; fewer mitochondria & less myoglobin 24) List 1 positive effect and 3 negative effects of anabolic steroids. Positive: builds/maintains muscles for those at risk for atrophy Negative: depression; gynecomastia (for men); infertility; decreased teste size; liver cancer; damage to heart and kidneys; changes to blood cholesterol 25) How/why do the following conditions affect the muscular system? Lou Gerhig s Disease (ALS): loss of motor neurons; When the motor neurons die, the ability of the brain to initiate and control muscle movement is lost. With voluntary muscle action progressively affected, patients in the later stages of the disease may become totally paralyzed. Botulism: toxin produced by a specific bacteria prevents release of ACh at neuromuscular junction which causes paralysis Myasthenia gravis: when the immune system is acting faulty & produces antibodies that block the ACh receptors on the muscle fiber Muscular Dystrophy: abnormal genes (mutations) interfere with the production of proteins needed to form & maintain healthy muscle; leads to progressive weakness & loss of muscle mass Atrophy: degeneration & loss of muscle mass Spasm: muscle cramp