Exam 2 Posted Answers

Exam 2 Posted Answers - BISC 307 Spring 2009 Exam 2 Answers...

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BISC 307 – Spring 2009 Exam 2 Answers 4 pts. 4 pts. 6 pts. 5 pts. 1. Indicate whether each of the following statements is true or false by writing the word “True” or “False” in the blank. Do not write T or F. ANS: a-T, b-T, c-F, d-T ________ a. Dihydropyridine receptors are voltage sensors in the transverse tubule membrane. ________ b. Type I skeletal muscle fibers contain large numbers of mitochondria. ________ c. When a muscle fiber undergoes an isotonic contraction, the spacing between z-disks remains constant. ________ d. Skeletal muscle fibers with more Ca 2+ pumps in the sarcoplasmic reticulum will relax more quickly following a twitch. 2. Write one number in each blank, to best match each of the steps in skeletal muscle contraction (on the left) with its functional significance (on the right). _______ a. Ca 2+ pumping into SR 1. breaks the cross-bridge _______ b. binding of ATP to myosin 2. terminates cross-bridge cycling _______ c. release of P i 3. causes depolarization of transverse tubules _______ d. binding of Ca 2+ to troponin 4. causes rigor mortis 5. change in myosin conformation causing filaments to slide 6. forms the cross-bridge ANS: a-2, b-1, c-5, d-7 7. trigger that initiates cross-bridge cycling 3. Briefly explain how a muscle can contract and lengthen at the same time, and give an example of such a contraction. ANS: If the load placed on a muscle exceeds the force the muscle generates, then the muscle will extend while contracting. There are many possible examples, but typical ones would be contractions of anti-gravity muscles in the legs when walking downhill or landing from a jump off a platform. -- note change in printing order – 5. Which one of the following comparisons between single unit and multiunit smooth muscle is correct? (d) a. Single unit smooth muscle receives mainly parasympathetic innervation, and multiunit receives mostly sympathetic innervation. b. Single unit smooth muscle cells have only muscarinic cholinergic receptors, and multiunit smooth muscle cells have only adrenergic receptors. c. In single unit smooth muscle, neurotransmitter is released from varicosities along the length of axons, and in multiunit smooth muscle, neurotransmitter is released only at the terminals (ends) of axons. d. Single unit smooth muscle cells are coupled by gap junctions, and multiunit smooth muscle cells are not coupled by gap junctions. e. Myosin light chain kinase activates contraction in single unit smooth muscle, and troponin-tropomyosin activates contraction in multiunit smooth muscles.
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NAME_______________________________________ 4. In both skeletal muscle and smooth muscle, Ca 2+ ions act as the trigger for contraction, but the sources, mechanisms, and fate of Ca 2+ is different in some important ways. Compare and contrast the following aspects of Ca 2+ -dependent contraction in smooth muscle and skeletal muscle: a. sources of Ca 2+ ions that trigger contraction (where do the Ca
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Exam 2 Posted Answers - BISC 307 Spring 2009 Exam 2 Answers...

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