Question

which fibers dominate many of the back and calf muscles that contract almost continually to maintain posture?
slow-twitch
fast-twitch
intermediate
question 10
1 pts
when a skeletal muscle fiber is at rest, there is more sodium outside the cell as compared to the sarcoplasm.
true
false

Explanation:

For the first question, slow - twitch fibers are endurance - oriented. They can contract for long periods without fatigue, which is suitable for maintaining posture (continuous contraction). Fast - twitch fibers are for quick, powerful contractions (e.g., sprinting), and intermediate fibers have a mix of properties but are not the best for continuous low - intensity contraction like posture maintenance.
For the second question, in a resting skeletal muscle fiber, there is a concentration gradient. Sodium (\(Na^{+}\)) is more concentrated outside the cell (in the extracellular fluid) compared to the sarcoplasm (intracellular fluid). This is due to the action of the sodium - potassium pump (\(Na^{+}/K^{+}\) - ATPase) which actively transports \(Na^{+}\) out of the cell.

Answer:

Slow - twitch, True