A. Helix the hv fab gbb b c u in by
A. Calcium would be sent to the sarcoplasmic reticulum, causing contractions to stop. A muscle fiber ceases to contract the instant ATP is depleted. Furthermore, contraction halts when signals from the motor neuron stop, leading to the repolarization of the sarcolemma and T-tubules, thus closing the voltage-gated calcium channels in the sarcoplasmic reticulum. Calcium ions are subsequently pumped back into the sarcoplasmic reticulum, allowing tropomyosin to once again obstruct the binding sites on the actin filaments.