BIO241 Muscle questions

LABORATORY 10 MUSCLE TISSUE SECTION 2: STRUCTURE OF A SKELETAL MUSCLE FIBER A. A muscle fiber, or muscle cell, is cylindrical in shape and is surrounded by the sarcolemma, or cell membrane . Inside the cell is the cytoplasm, or sarcoplasm, which contains numerous oval nuclei, mitochond ria, and myofibrils. Myofibrils play a fundament al role in muscle contraction . They contain overlapping thick and thin filaments. The thick filaments are composed of the protein myosin. The thin filaments are composed of the protein actin, in association with the regulatory proteins tropomyos in and troponin. The filaments are arranged in compartme nts called sarcomeres, which are the basic contractile units of a myofibril. A membrano us network called the sarcoplasmic reticulum surrounds the myofibrils and stores calcium ions, which are required for muscle contraction . Label the parts of the muscle fiber in Figure 10.2. 3 4 2 I 5 •••••••••••••••················· Openings in transverse tubules ©Van-Griner, LLC FIGURE 10.2 – Skeletal Muscle Fiber TERMS FOR FIGURE 10.2 Sarcomere Sarcolemma Myofibril Mitochondrion Sarcoplasmic reticulum Transverse tubules I. 4. 2. 5. 3. 6. BIOL 241 & BIOL 242 I HUMAN ANATOMY AND PHYSIOLOGY 129 LABORATORY 10 MUS CLE TISSUE I I 9 \ …. •·.. FIGURE 10.3 Structure of the Sarcomere TERMS FOR FIGURE 10.3 Sarcomere I band A band 1. 2. 3. 4. · Thick filament Thin filament Z line (disc) M line H band (zone) Titin 6. 7. 8. 9. 5. Y AND PHYSIOLOGY 131 BIOL 241 & BIOL 242 I HUMAN ANATOM LABORATORY 10 MUSCLE TISSUE SECTION 4: MUSCLE PHYSIOLOGY ly the missing terms in the following activities regarding muscle . b . d banks to complete the following statements. Answers may e used th h ·ology. Use e wor · . . . p ysi b Wh n you finish these activities, verify your answers with your instructor. more than once. e Use },our text to heIp you supp THE NEUROMUSCULAR JUNCTION In order for skeletal muscles to contract, they must first receive “messages” from motor neurons of the brain and spinal cord. The motor neurons carry the message in the form of an electrical signal called an (1) _ _ _ _ _ _ _ _ _ _ to the place where the neuron communicates with the muscle fiber called the (2) __________ or NMJ. The NMJ consists of three parts: (1) the end of the motor neuron, or (3) – – – – – – – – – ~ (2) the specialized area of the muscle fiber’s sarcolemma called the (4) __________, and (3) the gap in between called the (5) _ _ _ _ _ _ _ _ _ Transmitting the electrical signal across the gap requires a chemical messenger called a (6) _ _ _ _ _ _ _ _ _____, The neurotransmitter for skeletal muscle is called (7) __________ or ACh. _r WORD BANK 1-7 Acetylcholine Axon terminal Motor end plate Action potential Neurotransmitter Neuromuscular junction Synaptic cleft When an (BJ _ _ _ _ _ _ _ _ reaches the (9) _ _ _ _ _ _ _ _ _ of a motor neuron, vesicles stored in the cytoplasm of the motor neuron release (10) _ _ _ _ _ _ _ __ into the (11) _ _ _ _ _ _ _ ___, This diffuses across the (12) _ _ _ _ _ _ __ and binds to (13) _ _ _ _ _ _ _ _ on the (14) . This causes (15} _ _ _ _ _ _ _ _ channels in the sarcolemma to open, and (16) _ _ _ _ _ _ __ ions from the extracellular fluid rush into the cytoplasm of the muscle cell. This results in the generation of an action potential in the muscle cell. WORD BANI( 8-16 Synaptic cleft Sodium Motor end plate Action potential Acetylcholine Receptors Axon Terminal LABORATORY 10 MUSCLE TISSUE V has been genera ted in the muscle cell, (18) must be removed from the (19) and closes the sodium An enzym e called (20) _ _ _ _ _ _ _ _ _ breaks down ACh anothe r signal, anothe r chann els in the·sarcol emma . In order for the muscle cell to receive neuron . (21) ___ ___ ___ _ must be genera ted by the motor After the (17) WORD BANK 17-21 Synaptic cleft Action potential Acetylcholine Acetylcholinesterase THE SLIDING FILAMENT THEORY OF MUSCLE CONTRACTION en the thick and thin The force produ ced by muscle contraction is due to the interaction betwe When the thick and thin filaments slide filaments within the (1) ning of the sarcomeres in past each other, the (2) _ _ _ _ _ _ _ _ _ shortens. The shorte As multiple muscle each myofibril results in the shorte ning of the muscle cell (muscle fiber). The overall process is fibers contra ct, the muscle pulls on its attachments, moving a body part. stand this process, we called the slidingfilame nt theory of muscle contraction. In order to under nts and the steps involved must take a closer look at the struct ure of the thick and thin filame in contra ction. – – – – – – – – – J Thin filaments are comp osed prima rily of the protei n (3) as well as the regula tory protei ns (4) _ _ _ _ _ _ _ _ and (5) . The myosin head has two Thick filame nts are comp osed of the protei n (6) . bindi ng sites, one for (7) _ _ _ _ _ _ _ _ and the other for (8) the myos in heads into the In a restin g sarcom ere, the energ y from ATP is used to activate . (9) high energ y confo rmati on requi red to engage the bindi ng sites on _ _ _ _ _ _ _ which in These bindi ng sites are covered by the regula tory protei n (10) _ _ ———–!• turn is held in place by (11) _ _ _ _ _ _ ___, WORD BANK 1-11 ATP Tropomyosin Myofibrils Myosin Actin Sarcomere Troponin BIOL 241 & BIOL 2421 HUMAN ANATOMY AND PHYSIOLOGY 133 I~ l ,.J. ~· • LABORATORY 10 MUSCLE TISSUE • I :d:J~ r.L ~) When an action potential is produced in the sarcolemma of the motor end plate, it travels down the (12) _ _ _ _ _ _ _ _ _ (T-tubules) into the (13) _ _ _ _ _ _ _ ____, This triggers the release of (14) _ _ _ _ _ _ _ _ _ _ ions into the sarcoplasm. Calcium binds to (15) _ _ _ _ _ _ _ _ ___, which causes a conformational change, moving (16) _ _ _ _ _ _ _ _ _ away from the (17) _ _ _ _ _ _ _ _ _-binding sites on actin. The energized myosin heads now bind to the exposed sites on actin, forming (18) . The heads then flex, producing a ratcheting motion known as the (19) . This causes the thin filaments to slide past the thick filaments, pulling the ends of the sarcomere closer together and causing the muscle cell to contract. The (20) _ _ _ _ _ _ _ _ _ _ head now binds another molecule of (21) _ _ _ _ _ _ _ _ _ _ releasing myosin from the (22) _ _ _ _ _ _ _ _ __ binding site. As long as (23) _ _ _ _ _ _ _ _ _ _ ions are present and (24) _ _ _ _ _ _ _ _ _ _ is available to supply energy, this process repeats over and over, and muscle contraction continues. Power stroke Calcium Sarcoplasmic reticulum Actin I . •·• i • ;~ 1 ~ ·.,., (‘ I ‘ , ·-· ::,: ‘ j •J. • :~ I ‘.~ I ,• ~-,, .. I , ‘•rit ,Ctl I Myosin Transverse tubules Troponin ATP Tropomyosin Cross-bridges leti I (t MUSCLE RELAXATION In order for muscle relaxation to occur, the steps that caused muscle contraction must be reversed. First, the motor neuron must stop producing (1) (2) _ _ _ _ _ _ _ _ _ is no longer released from the (3) _ _ _ _ _ ____, . (4) ions are actively transported from the sarco- plasm back into the (5) – – – – – – – – – – – J This removes the calcium from (6) _ _ _ _ _ _ _ _ _ and moves (7) _ _ _ _ _ _ _ _ _ back to cover the (8) _ _ _ _ _ _ _ _ _-binding sites on (9) Now that (10) _ _ _ _ _ _ _ _ _ heads can no longer bind to (11) _ _ _ _ _ _ _ _ _ , the thick and thin filaments disengage and slide back. The sarcomere lengthens, and the muscle cell relaxes. WORD BANK 1-11 Troponin Myosin Axon terminal Tropomyosin Calcium Acetylcholine Actin Action potentials Sarcoplasmic reticulum (t I I (4 I I~ I (~ I I I I I NAME: 3: -> w w 11:1: m ,c -a I I I • LAB PARTNER: DATE: SECTION: MUSCLE TISSUE PART A Matc h the term with its corre ct description. 1. _ 2. _ 3. _ 4. A. Sarcolemma Attaches muscle to bone Com pone nt of thick filament B. Sarcomere C. Sarcoplasm Com pone nt of thin filament Cyto plasm of a muscle cell D. Sarcoplasmic reticulum E. Endomysium 6. Func tiona l unit of a myofibril Cell mem bran e of a muscle cell 7. Bund le of musc le fibers 8. Prod uces ATP for muscle contr actio n Conn ectiv e tissu e that surro unds an indiv idual 5. F. Perimysium G. Epimysium H. Fascicle I. Tend on musc le fiber J. Fascia Conn ectiv e tissu e that separ ates muscle into fascicles Conn ectiv e tissu e that bind s adjacent muscles into K. Myofibril func tiona l grou ps M. Myosin N. Actin 13. Conn ectiv e tissu e surro undi ng a skeletal muscle Cellu lar orga nelle that store s calci um ions 14. Cont racti le orga nelle in muscle cells 9. 10. 11. 12. L. Mito chon drion Y 137 BIOL 241 & BIOL 242 HUMAN ANATOMY AND PHYSIOLOG — — — ..– ·• — w c· –~~ :- — ~ Mi ~, – a . -~~:n, -. — ~— ~-. ·-·’I LAB REVIEW 10 MUSCLE TISSUE I CLINICAL CONNECTION I. List three ways ATP is used in muscle contr actio n and relaxation. a. b. c. 2. Wha t is rigor mortis? 3. Wha t is the role of ATP and calcium in causi ng this cond ition ?

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