True or False: A rise in cytosolic {eq}Ca_2+ {/eq} is required for contraction of all 3 muscle types.

Question:

True or False: A rise in cytosolic {eq}Ca_2+ {/eq} is required for contraction of all 3 muscle types.

Muscle Contraction:

There are three types of muscle tissue, cardiac, smooth and skeletal muscle. All muscle tissue is excitable and upon activation contracts; this contraction is due to the sarcomere shortening when myosin moves relative to actin.

Answer and Explanation: 1

True. Calcium is required for contraction in all muscle tissues to create the cross-bridge and allow the actin and myosin filaments to slide relative to each other to shorten the sarcomere and produce a muscular contraction. Skeletal and cardiac muscle tissue have a similar contraction mechanism. The calcium is needed to bind to the troponin/tropomyosin complex which, when calcium is bound, will undergo a conformational change that exposes actin active sites. Myson heads can then bind to actin and with the energy provided by ATP slide relative to each other to create muscle tension. In smooth muscle cells, calcium binds to calmodulin which binds to myosin light chain kinase. Myosin light chain kinase phosphorylates myosin heads so they can form the cross-bridge with actin and slide relative to each other to create muscle tension.


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Muscular Contraction: Cross-Bridge Formation

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Chapter 14 / Lesson 3
65K

Discover the cross-bridge cycle and its stages. Identify what a cross-bridge muscle contraction is and learn about the role of ATP in cross-bridge cycling.


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