ANATOMY & PHYSIOLOGY
4th Edition
ISBN: 9781264719969
Author: McKinley
Publisher: MCG
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Textbook Question
Chapter 10, Problem 4CAL
Rigor mortis occurs following death because
- a. tropomyosin remains over the myosin binding sites of actin.
- b. myosin heads attach to actin and are not released due to lack of ATP.
- c. the myosin becomes misshapen.
- d. all of the Ca2+ remains within the sarcoplasmic reticulum.
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Rigor mortis occurs following death because a. tropomyosin remains over the myosin binding sites of actin. b. myosin heads attach to actin and are not released due to lack of ATP. c. the myosin becomes misshapen. d. all of the Ca2+ remains within the sarcoplasmic reticulum.
The functions of tropomyosin in skeletal muscle include
A. releasing calcium ions after initiation of contraction.
B. generating ATP which it passes to the contractile mechanism.
C. binding to myosin during contraction.
D. acting as a relaxing protein at rest by covering up the sites where myosin binds to actin.
E. sliding on actin to produce shortening.
The binding of calcium to troponin will directly cause
A. the hydrolysis of ATP
B. the binding of ATP to myosin
C. the further release of calcium into the cytoplasm
D. the movement of tropomyosin, thereby exposing the myosin-binding site on the actin molecule
E. the movement of tropomyosin, thereby exposing the actin-binding site on the myosin molecule
F. release of neurotransmitters from the axon terminals
G. Both B and F
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- For relaxation to occur, A. calcium leaves the sarcoplasmic reticulum, and troponin binds calcium and blocks the binding sites on actin. B. calcium enters the myofibril, it detaches from myosin, and the binding sites on myosin become inactive. C. sarcoplasm calcium levels fall, calcium is removed from troponin, and tropomyosin blocks binding sites on actin. D. extracellular calcium levels fall, calcium is pumped into the myofibril, and tropomyosin slides away from actin.arrow_forwardthe troponin/tropomyosin complex will inhibit the crossbridges of myosin from with actin. this is true during: A. Muscle relaxation B. Muscle contraction C. Nerve stimulation D. Both a & barrow_forwardThe sliding filament mechanism describes the process during which: a. actin and myosin slide relative to each other b. sarcomeres slide relative to each other c. troponin and tropomyosin slide relative to each other d. muscle fibers slide past each otherarrow_forward
- Which of the following statements about the Ca2+ release channels in the sarcoplasmic reticulum is false? a.They are also called ryanodine receptors. b.They are one-tenth the size of the voltage-gated Ca 2+channels. c.They are opened by Ca2+release channels in the transverse tubules. d.They permit Ca 2+ to diffuse into the sarcoplasm from the sarcoplasmic reticulum.arrow_forwardIn the presence of myosin cross-bridges are able to bind to complementary sites on the actin filaments, thereby forming the so-called actin-myosin complex. O a. Tropomyosin O b. Ca2+ O c. ATP O d. Troponin TOSHIBAarrow_forwardPut the following skeletal muscle contraction events in the order that they occur: a. The myosin head swivels toward the center of the sarcomere. b. Calcium ions are released from the sarcoplasmic reticulum and bind to troponin. c. An action potential is propagated along the sarcolemma and transverse tubules. d. Myosin binds to actin, forming crossbridges. e. Myosin heads bind ATP molecules and release from actin. f. Tropomyosin molecules are moved off active sites on actin. g. ATPase splits ATP, providing the energy to reset the myosin head.arrow_forward
- Which of the following are involved interaction of myosin and actin? A. interaction between the myosin head and the myosin binding site on actin B. requires troponin to go through a conformational change pulling topomyosin from its resting position C. all of the above D. occurs when topomyosin is pulled away from the myosin binding site on actinarrow_forwardWhich of the following statements is true of the chameleon tongue but not of the human tongue? A. It is a muscular hydrostat. B. Force generation reflects the binding of myosin crossbridges to actin thin filaments. C. The organization of the actin and myosin filaments produces a regular pattern of bands, or striations. D. Gaps or holes in the Z-discs allow supercontraction (shortening beyond the normal limit). E. All of the above statements are true of both the chameleon tongue and the human tongue.arrow_forwardThe function of Ca2+ in skeletal muscle contraction is toa. cause an allosteric change in myosin so it detaches from actin.b. provide the energy necessary for the movement of the cross-bridge.c. expose the myosin-binding sites on the thin filaments.d. bind to tropomyosin.e. do a and c only.arrow_forward
- When a skeletal muscle cell contracts and the muscle shortens, a. the position of an actin molecule relative to a myosin molecule does not change. b. myosin heads generate a single power stroke. c. the actin ATPase allows the actin molecule to swivel. d. the actin molecule swivels during the power stroke e. some myosin heads are forming crossbridges as others are releasing them.arrow_forwardMyosin binds to actin, then bends. What is ATP needed for next? A. to pump the Ca++ “keys” back into the sarcoplasmic reticulum B. to replace the strap and cover the binding sites C. to give feedback to the neuron that contraction occurred D. to un-bind myosin from actin and re-set for another powerstroke.arrow_forwardWhat role (function) does calcium have within a muscle fiber? a. trigger muscle potentials along t-tubules b. trigger contraction by causing the formation of cross bridges c. trigger exocytosis of ACh across the synaptic space d. trigger action potentials along axons e. open voltage gates within the sarcoplasmic reticulum 2. Which of the following are regulatory proteins that allow a muscle fiber to contract when calcium is present? (select all that apply) dystrophin troponin myosin tropomyosin actin 3. During this phase of an action potential, potassium ions exit the cell through voltage gated potassium channels. a. depolarization b. repolarization c. glycolysis d. cross bridge formationarrow_forward
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