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25 Cards in this Set
- Front
- Back
During contraction, the parallel thick and thin filaments of the myofibrils are connected by __________ that span the space between the parallel thick and thin filaments. |
crossbridges |
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Caveolae are important because they contain |
voltage-regulated Ca2+ channels which allow Ca2+ entry into the muscle cell. |
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A contraction that generates force and moves a load is known as __________, |
isotonic |
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Whereas one that generates force without movement is known as __________. |
isometric |
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A motor unit consists of |
one neuron and the muscle fibers it controls |
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After death, when metabolism stops, in which step of the contractile cycle will skeletal muscles remain stuck if they have been contracting, for most of the first day or so? |
the rigor state |
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An important difference between single-unit and multiunit smooth muscle is |
numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet. |
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As ATP binds to the myosin head at the beginning of a muscle contraction cycle, |
the myosin head detaches from actin. |
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At the conclusion of the power stroke, |
inorganic phosphate has been released from the myosin. actin has been moved toward the M line. ADP is released from the myosin head. the myosin head is tightly bound to actin. |
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Compared to skeletal muscle, smooth muscle in a latch state |
is slower to contract in response to a stimulus and sustains contractions longer without fatigue |
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For striated muscle, each myosin head (leaflet) has |
a binding site for an ATP molecule, a binding site for an actin molecule, and the ability to swivel (rachet) when powered by ATP |
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Excitation-contraction coupling refers to |
the chemical and electrical events form the neuron inwards that trigger the contractile events in a muscle fiber. |
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In smooth muscle, what is the small protein chain that regulates contraction and relaxation? |
myosin light chain kinase (MLCK) |
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Complete the following sentence to describe the state of relaxed muscle fibers: myosin heads are |
not bound to actin, and contain ADP and Pi. |
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One of the major differences among skeletal muscle fiber types is in their resistance to fatigue. The fibers with the most endurance rely on __________ for energy. |
oxidative phosphorylation |
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Regulation of cross-bridge formation in striated muscle is accomplished by |
tropomyosin, troponin, and calcium ions |
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Smooth muscle cells lack which protein(s)? |
troponin |
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Striated muscles are so-called because of a repeating pattern of light and dark bands. One repeating unit of the banding pattern is called a |
sarcomere |
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The H zone contains |
thick filaments |
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The I band contains |
thin filaments |
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For both striated and smooth muscle the contraction cycle is triggered by the rise in __________ in intracellular fluid. |
Ca2+ |
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The period of time during which the sarcomeres return to their resting length is referred to as |
the relaxation phase |
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When the membrane potential of a cell is resting which of the following ions are at equilibrium? |
Cl- |
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The resting membrane potential of cells appears to have resulted as a solution to what problem? |
The need to have the same quantity of solute on either side of the membrane. |
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A pharmacomechanical coupling in smooth muscle results in no change in the membrane potential. |
true |