18. Given an Action Potential to initiate the sequence of events for a skeletal
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Question
18. Given an Action Potential to initiate the sequence of events for a skeletal muscle which ion is released from the terminal cisternae of the Na"* K' CT Ca" reticulum into the sarcoplasm? sarcoplasmic C. D. 19. True or False. Correct if False: When an alpha-motor neuron is activated, only the most excitable skeletal fibers in the activated Motor Unit are stimulated to contract. A. True. 8. False. All of the muscle fibers in its motor unit are stimulated to contract C False. The presence of the intercalated discs cause contraction of several nearby motor un 20. True or False. Correct if False: are categorized as Cardiac and Smooth Muscle types are categorized as "Voluntary" Muscles A. True B. False. Skeletal and Cardiac are "Voluntary" Muscles C. False. Skeletal Muscles only are "Voluntary. True or False. Correct if False: Skeletal and Cardiac Muscles are striated. A. True. B. False. Smooth and Skeletal are striated. 21. C. False. Smooth and Cardiac are striated. With an isometric contraction (muscle tension only without muscle shortening), t myofilaments slide toward the center of the sarcomere. A. True. B. False. The myosin myofilaments slide toward the center of the sarcomere. C. False. The cross-bridges of actin and myosin myofilaments engage, but no 22. True or False. Correct if False: the myosin takes place. 23. True or False. Correct if False: A muscle contraction begins when acetylcholine release onto the sarcolem bouton of the alpha-motor neuron ceases. A. True. B. False. A muscle contraction begins when Ca+ is released into the sar molecule alone to uncover its bonding sites C. False. A muscle contraction begins when Ca is released into the sa tropomyosin molecule to move the troponin molecule, thusExplanation / Answer
18. Terminal cisternae are enlarged sacs in sarcoplasmic reticulum that are in contact with transverse tubules. They are storage sites for calcium. Calcium is released from these storage sites into the sarcoplasm when the skeletal muscle is stimulated by action potentials. Removal of calcium ions (Ca2+) from the sarcoplasm is linked to the breakdown of ATP. The free energy of hydrolysis of ATP provides the energy for the Ca2+ transport.
Option D.
19. Alpha motor neurons are neurons that innervate extrafusal fibers that lie in a skeletal muscle. They are responsible for contraction of skeletal muscles. There are three types of extrafusal fibers present in skeletal muscles. However, all muscle fibers in one motor unit will have only one type of extrafusal fibers as determined by the myotrophic influences of the neuron. Hence, the statement is false. Activation of alpha motor neurons will cause all muscle fibers in a motor unit to contract.
Option B.
20. Cardiac and smooth muscles are involuntary muscles, as their muscle contraction or expansion occurs all the time. Their actions are not based on body movements or under the person’s control. Skeletal muscle movements are voluntary, attached to the skeleton.
Option C.
21. Cardiac and skeletal muscles are striated muscles composed of highly organized contractile myofilaments. Actin and myosin myofilaments are organized in an regular repeating arrays of sacromeres. Where the myofilaments overlap, a dark band is seen and when they do not overlap, a light band will be seen.
Option A.
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