Excitation-Contraction Coupling.

Question 1

If the cross-bridge is too low:

Answer 1

The cycle is arrested after ATP hydrolysis; before the cross-bridge binds to thin filaments.

High affinity for the thin filament.

Question 2

Tropomyosin prevents cross-brides from binding by:

Answer 2

Blocking myosin binding sites in the thin filaments.