The System of Flexing and Extending Muscles Makes Movement of Appendages

question 31

Multiple Choice

The system of flexing and extending muscles makes movement of appendages easy to understand.But how are some actions possible (sticking out your tongue,beating of your heart) when these structures have no bone structure with opposing flexors and extensors in them?

• A)One set of muscle cells must therefore be able to both contract and expand.
• B)These structures must be empty chambers,and fluids forced into them expand them.
• C)Muscle cells running diagonally or crosswise amidst the longitudinal muscles must contract and force the long relaxed muscle cells to elongate.
• D)This cannot be explained at present.

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Definitions:

Average-Total-Cost Curve

Graphical representation that shows how the average total costs of production change as the quantity of output is altered.

Average-Fixed-Cost Curve

A graphical representation that shows how the average fixed costs of production decrease as the quantity of output increases, due to spreading fixed costs over a larger number of units.

Average Total Cost

Average total cost is the total cost of production divided by the quantity of output produced, including both fixed and variable costs.

Average Variable Cost

The total variable costs (costs that change with the level of output) divided by the quantity of output produced.