Human Phys TA Lecture 8 Answers PDF

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Block 2, Lecture 8 Practice Questions, Dr. Sved...

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TA Answers 9/19/13 Striated Muscle - Lecture 8 1. Name the filaments (actin, myosin, both) that are found in the following areas: -

Z-line: thin filaments (marks boundaries of sarcomere)

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I band: thin filaments only

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A band: thick and thin filaments

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H zone: thick filaments only

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M line: thick filaments (marks center of sarcomere)

2. Define the following terms: -

Sarcolemma: the membrane around a muscle fiber (from the fusion of myoblasts)

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Sarcoplasm: the cytoplasm of muscle fibers

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sarcoplasmic reticulum: endoplasmic reticulum in muscle, vital for calcium dynamics

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T-tubules: extensions of the sarcolemma that extend deep into the muscle fiber

3. Describe the role that calcium plays in the cross bridge cycle during contraction of muscle. It binds to troponin, which stops the blocking action of tropomyosin. This allows the activated myosin head to bind to the actin filament. (Slide 13) 4. Describe the events of one cross bridge cycle. Starting with the myosin bound to the actin filament, ATP will bind to the myosin head, which causes the myosin head to detach from actin. The ATPase activity of the myosin will allow the head to swing over and weakly bind to the actin filament. Release of inorganic phosphate will cause it to swing over (power stroke), moving the actin filament towards the M line. The myosin head will then release ADP, allowing a tight bond between the two proteins (rigor state). (Slide 10)...