Question

question 16 (1.7 points)
why is the contraction strength of smooth muscle relatively independent of its resting length?
it gets nearly all of its ca²+ from the extracellular fluid.
it does not have intercalated discs.
it does not have sarcomeres.
it is regulated by a length - tension relationship.
it is involuntary muscle.

Explanation:

Smooth muscle contraction strength being independent of resting length is related to its structure. Sarcomeres are the basic contractile units in striated muscle (like skeletal and cardiac). Striated muscle's contraction strength is length - dependent due to sarcomere arrangement (length - tension relationship). Smooth muscle lacks sarcomeres. The lack of a fixed sarcomere - based structure means its contraction strength isn't as strictly tied to resting length as in striated muscle.

• The source of \(Ca^{2 +}\) (from extracellular fluid) is more about the activation mechanism of smooth muscle contraction rather than the length - strength relationship.
• Intercalated discs are found in cardiac muscle (for cell - to - cell communication), not relevant to smooth muscle's length - strength independence.
• While smooth muscle is involuntary, this is about its control (by autonomic nervous system etc.) not the length - strength relationship.
• The length - tension relationship is a characteristic of striated muscle (because of sarcomeres), not what makes smooth muscle's contraction strength independent of resting length.

Answer:

It does not have sarcomeres.