1. Action potentials are propagated to the interior of a musclefiber by extensions of the sarcolemma called the _______________.

2. The _______________ serves as a reservoir of calcium ions in skeletal muscle.

3. The thick myofilaments are composed of the protein _______________.

4. One motor neuron and all the muscle fibers innervated by itconstitute a/an _______________.

5. The synapse where a motor nerve fiber and muscle fiber meet iscalled a/an _______________.

6. Motor nerve fibers stimulate skeletal muscle fibers with asecretion called _______________.

7. A skeletal muscle fiber has a voltage of about -90 mV, called its_______________, across the sarcolemma.

8. When a muscle fiber is excited, its membrane produces a quick,self-propagating voltage change called a/an _______________.

9. Our best current understanding of how muscle contracts is calledthe _______________ theory.

10. Myosin cannot bind to actin until calcium binds to _______________ and _______________moves out of the way of the active sites on the actin.

11. When a muscle is stimulated so frequently it can't completelyrelax between twitches, the successive twitches become stronger and stronger. This iscalled _______________.

12. In _______________ contraction, a muscle develops or maintains tension evenas it is being stretched, thus preventing it from relaxing too quickly and producingabrupt, uncoordinated actions.

13. The difference between one's normal rate of oxygen consumptionand the rate seen at the end of a strenuous exercise is called _______________.

14. In _______________ smooth muscle, neighboring muscle cells are joined by gapjunctions and stimulate each other to contract.

15. Most sympathetic muscle fibers stimulate smooth muscle tocontract with the neurotransmitter _______________.

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