Human Physiology
15th Edition
ISBN: 9781259864629
Author: Fox, Stuart Ira
Publisher: Mcgraw-hill Education,
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Chapter 12, Problem 10RA
Summary Introduction
To determine:
The correct statement about the cross-bridges.
Introduction:
Cross bridge is the most important process involved in muscle contraction. It shows how the actin and filaments move relative to each other. The actin and myosin filaments bind to each other in order to cause sarcomere shortening, hence muscle contraction.
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In muscle cells, magnesium ions compete with calcium ions for binding sites on troponin molecules. If a person has too high a concentration of magnesium ions in the blood, magnesium ions can prevent calcium ions from binding troponin.
A) What effect would this have on muscle contraction (strengthen, weaken, or no effect)?
B) Use your knowledge of how muscle fibers contract to explain your answer in part A.
Myosin 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.
Which is a false statement about skeletal muscle structure?a. A myofibril is composed of multiple muscle fibers.b. Most skeletal muscles attach to bones by connective-tissue tendons.c. Each end of a thick filament is surrounded by six thin filaments.d. A cross-bridge is a portion of the myosin molecule.e. Thin filaments contain actin, tropomyosin, and troponin.
Chapter 12 Solutions
Human Physiology
Ch. 12 - Describe the actions of muscles when they...Ch. 12 - Describe the different levels of muscle structure,...Ch. 12 - Define the terms motor unit and innervation ratio...Ch. 12 - Using the concept of recruitment, explain how...Ch. 12 - With reference to the sliding filament theory,...Ch. 12 - Prob. 3bCPCh. 12 - Describe a cycle of cross-bridge activity during...Ch. 12 - Prob. 4bCPCh. 12 - Use a flowchart to show the sequence of events...Ch. 12 - Prob. 5bCP
Ch. 12 - Explain how graded contractions and smooth,...Ch. 12 - Prob. 6bCPCh. 12 - Prob. 7aCPCh. 12 - Describe the relationship between the resting...Ch. 12 - Prob. 8CPCh. 12 - Prob. 9CPCh. 12 - Explain the different causes of muscle fatigue...Ch. 12 - Prob. 11CPCh. 12 - Prob. 12aCPCh. 12 - Describe all of the events that occur from the...Ch. 12 - Prob. 13CPCh. 12 - Explain the significance of reciprocal innervation...Ch. 12 - Describe the functions of gamma motor neurons and...Ch. 12 - Explain how cardiac muscle differs from skeletal...Ch. 12 - Contrast the structure of a smooth muscle cell...Ch. 12 - Distinguish between single-unit and multiunit...Ch. 12 - Describe the events by which depolarization of a...Ch. 12 - Prob. 1RACh. 12 - Prob. 2RACh. 12 - Prob. 3RACh. 12 - Prob. 4RACh. 12 - Prob. 5RACh. 12 - Prob. 6RACh. 12 - Prob. 7RACh. 12 - Electrical excitation of a muscle fiber most...Ch. 12 - The energy for muscle contraction is most directly...Ch. 12 - Prob. 10RACh. 12 - Prob. 11RACh. 12 - Prob. 12RACh. 12 - Which of these types of muscle cells are not...Ch. 12 - Prob. 14RACh. 12 - In an isotonic muscle contraction,...Ch. 12 - Prob. 16RACh. 12 - Prob. 17RACh. 12 - Prob. 18RACh. 12 - Using the concept of motor units, explain how...Ch. 12 - Prob. 20RACh. 12 - Explain why the myosin heads don't bind to the...Ch. 12 - Using the sliding filament theory of contraction,...Ch. 12 - Prob. 23RACh. 12 - Prob. 24RACh. 12 - Prob. 25RACh. 12 - What changes occur in muscle metabolism as the...Ch. 12 - Prob. 27RACh. 12 - Compare cardiac muscle, single-unit smooth muscle,...Ch. 12 - Your friend eats huge helpings or pasta for two...Ch. 12 - Prob. 30RACh. 12 - Prob. 31RACh. 12 - How is electrical excitation of a skeletal muscle...Ch. 12 - Prob. 33RACh. 12 - Prob. 34RACh. 12 - Prob. 35RACh. 12 - Prob. 36RACh. 12 - Refer to figure 12.22 to answer the following...Ch. 12 - Refer to figure 12.22 to answer the following...Ch. 12 - Prob. 39RACh. 12 - Refer to figure 12.22 to answer the following...
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- Outline the role of calcium ions on muscle contraction during a biceps curl. In your answer: A) Describe the role of the nervous system in stimulating the release of calcium ions. b) Outline the role calcium ions play in the 'sliding filament theory?'arrow_forwardWhich statement about striated skeletal muscle is true? A. The tension generated by a muscle is invariable. B. Mechanical summation of twitches in a muscle fiber leads to a graded increase in the tension that is above that generated by a single twitch. C. A single action potential arriving at the neuromuscular junction is not sufficient to cause a muscle fiber to twitch. D. Muscle twitches are able to mechanically sum when Ca2+ is quickly and completely removed from the sarcoplasm between action potentials. E. An action potential in the muscle cell activates contraction by releasing Na+ into the sarcoplasm.arrow_forwardWhat does ATP binding to myosin head triggers? a. Its association with microtubules b. Its dissociation from actin microfilament c. Conformational change and rotation of myosin head d. Its association with actin microfilamentarrow_forward
- The 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_forwardPredict what might happen to a muscle cell that is extensible but not elastic. What if the reverse were true— a muscle cell is elastic but not extensible?arrow_forwardDuring which phase of the crossbridge cycle is ATP split into ADP and Pi? A. Immediately preceding the detachment of the myosin head B. Immediately preceding the resetting of the myosin head C. Immediately preceding the power strokearrow_forward
- What event causes a troponin-tropomyosin complex to regain its original shape in muscle relaxation? a. stimulation of ACh receptors b. diffusion of Na+ back into transverse tubules c. return of Ca2+ into the sarcoplasmic reticulum d. breaking of the bond with tropomyosinarrow_forwardWhat happens when myosin filaments hydrolyze ATP molecules in muscles? a. Actin–myosin complexes dissociate, leading to muscle contraction. b. Actin–myosin complexes dissociate, leading to muscle relaxation. c. Actin–myosin complexes are formed, leading to muscle contraction. d. Actin–myosin complexes are formed, leading to muscle relaxation.arrow_forwardIf a muscle cell had very short T-tubules, how much tension would the muscle fiber create, relative to a normal muscle fiber? Assume sarcoplasmic reticulum can still react to activity at the neuromuscular junction. a)Less tension would be created. b) No difference in tension creation. c) More tension would be created. d) No tension would be created.arrow_forward
- Predict what would happen to skeletal muscles of the body if an individual exposed to chemicals that inhibited the ATPase activity of myosinarrow_forwardWhen sarcomeres contract during muscle contraction, which of the following occurs? A. The myosin filaments lengthen. B. The myosin filaments "walk" along the actin microfilaments. C. The myosin filaments shorten. D. The actin filaments shorten.arrow_forwardWhat is released when myosin heads attach to actin filaments A. Phosphate B. ATP C. ADP D. Tropomyosinarrow_forward
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