In a study of aging in dolphins that were stranded on the beach, researchers took muscle biopsies and stained them for the fast isoform of myosin heavy chain. (Blue = stain for the fast isoform). Image A on the left is from a young dolphin and Image B on the right is from an old dolphin. If you could use the muscles in an experiment similar to the one in Rome et al, which one would reach tetanus at a lower stimulation frequency? Justify your answer (3 sentences max)

In a study of aging in dolphins that were stranded on the beach, researchers took muscle biopsies and stained them for the fast isoform of myosin heavy chain. (Blue = stain for the fast isoform). Image A on the left is from a young dolphin and Image B on the right is from an old dolphin. If you could use the muscles in an experiment similar to the one in Rome et al, which one would reach tetanus at a lower stimulation frequency? Justify your answer (3 sentences max)

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter8: Muscle Physiology

Section: Chapter Questions

Problem 2TAHL

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Figure 38.37 Which of the following statements about muscle contraction is true? The power stroke occurs when ATP is hydrolyzed to ADP and phosphate. The power stroke occurs when ADP and phosphate dissociate from the myosin head. The power stroke occurs when ADP and phosphate dissociate from the actin active site. The power stroke occurs when Ca2+ binds the calcium head.
With regard to muscle contraction, which of the following is an INCORRECT statement with regard to the interactions of filaments that occur in the sarcomere? A. When muscles are relaxed tropomyosin blocks binding sites on actin subunits, which keeps cross-bridges from forming. B. The myosin heads conduct a power stroke motion to slide when bound to actin, to move the "thin" filaments towards the center of the sarcomere. C. During contraction, actin subunits are removed from the ends of the "thin" filaments to shorten actin polymers, thus reducing the length of the sarcomere. D. "Thick" filaments are anchored at the M-line, while "thin" filaments are anchored at the Z-line. E. Numerous myosin heads engage with the actin filaments simultaneously, such that there is no back-slipping during the contraction process.
The single-fiber twitch experiments shown here were generated by stimulating the muscle cell membranes to threshold with an electrode and measuring the resulting action potential and force. How would the results differ if Ca21 were removed from the extracellular solution just before the electrical stimulus was applied?
The sliding filament model depicts how myosin motors attached to actin lead to muscle contraction. This process proceeds in a precise series of events. Indicate which of the following shows the correct order of steps in the sliding filament model. Group of answer choices Myosin binds ATP; myosin tightly binds actin; power stroke; myosin releases actin Myosin binds GTP; myosin releases actin; power stroke; myosin tightly binds actin Actin binds ATP; power stroke; myosin tightly binds actin; actin releases ADP Actin binds ADP; myosin releases actin; power stroke; actin releases ADP
The role of tropomyosin in a muscle cell is to ____. all to cell to relax by blocking the binding sites on actin facilitate the formation of cross-bridges between actin and myosin Interactions between thick and thin filaments during muscle contraction occur in which sequence? "attach to actin, detach from actin, pivot in powerstroke, return or recock" "attach to actin, pivot in powerstroke, detach from actin, return or recock" "attach to actin, pivot in powerstroke, return or recock, detach from actin" "detach from actin,pivot in powerstroke, attach to actin, return or recock" What is the role of calcium pump in muscle contractions? pump calcium out of the sarcoplasmic reticulum against its concentration gradient to initiate contractions remove calcium from the fluid surrounding the myofibrils to end contractions pump calcium into the muscle cell to stimulate the release of acetylcholine
Which of the following step(s) about the excitation of skeletal muscle is/are incorrect? 1. Acetylcholine is released and binds to motor end plate receptors 2. An action potential is created and moves down T-tubules 3. Calcium is released from the sarcoplasmic reticulum 4. Calcium ions bind to tropomyosin to shift troponin off the binding sites for cross-bridging 5. Myosin forms cross-bridges and binds with actin to pull it towards middle of sarcomere
In the process called "excitation-contraction coupling" (the events that lead up to a muscle cell's contraction), what part of this process is disrupted by death? (Actually, all of it is disrupted by death, but we can pinpoint a linkage between death, and the onset of rigor mortis--as well as explaining why rigor mortis eventually ends.)
In the sliding filament theory of contraction, what prevents the filaments from sliding back to their original positions each time a myosin head releases to bind to next actin binding site?
In bending in the binding of the myosin head of the free binding site of the actin filament results in the contraction of the muscle
In the process of muscle contraction, which of the following steps immediately comes after the propagation of an action potential down the t-tubules of a myofiber? sliding of tropomyosin causing exposure of actin binding of myosin head to actin's active site release of calcium from the terminal cisternae binding of acetylcholine to its receptor influx of sodium at the sarcolemma
In the process of muscle contraction, which of the following steps requires hydrolysis of ATP to complete? movement of myosin head, pulling the thin filament binding of myosin head to active site on actin resetting of the myosin head back to its ready position letting go of myosin head from the active site on actin sliding of tropomyosin causing exposure of actin
Calmodulin is found in smooth muscle cells and performs a similar function to troponin in striated muscle fibers. However, calmodulin not only gets activated by Ca2+ but also slows the release of Ca2+ from the sarcoplasmic reticulum. How might this difference relate to the different kinds of contractions smooth muscles do in comparison to striated muscles?