Question

20200--PHYS- lab --Skeletal Muscle

1) What is the function of the sarcoplasmic reticulum? ______________________________________

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2) Describe the function of troponin and tropomyosin _____________________________________________________________________________________

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3) Why will overstretching a skeletal muscle result in less contractile force?________________________

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4) Which phase of skeletal muscle contraction is the most brief?________________________________

5) Which type of skeletal muscle fiber is the most prevalent in everyone? ________________________

6) Increasing voltage to a muscle will increase contraction force up to a limit-why? __________________

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7)   ______________ ___is the activation of additional motor units to accomplish increased contractile force.

8) What occurs during the latent phase of skeletal muscle contraction? ____________________________________________________________________________________

Answer 1

1.Sarcoplasmic reticulum (SR) regulates the cytoplasmic calcium ions (Ca2+) concentration of skeletal muscle cells, and thereby controls muscular contraction and relaxation.

2.Troponin is attached to the protein tropomyosin and lies within the groove between actin filaments in muscle tissue. In a relaxed muscle, tropomyosin blocks the attachment site for the myosin crossbridge, thus preventing contraction. When the muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic membrane and release calcium into the sarcoplasm. Some of this calcium attaches to troponin, which causes it to change shape, exposing binding sites for myosin (active sites) on the actin filaments. Myosin's binding to actin causes crossbridge formation, and contraction of the muscle begins.