1 In skeletal muscle cells crossbridge cycling will continue

1. In skeletal muscle cells, cross-bridge cycling will continue as long as the calcium concentration of the cytosol remains elevated. T/F

2. In an isotonic contraction in which the force is greater than the load on a muscle, the Z lines move closer together. T/F

Solution

1.the number of active cross bridges is a function of ca++ concentrarion ,hence in elevated level of concentration of ca++ ions the cross bridge cycling will continue which causes contraction of muscle cells, but ca++ has to be pumped out of the cell since relaxation of the cells is needed.

The answer is T.

2.when the contractile forces exceeds the load,shortening begins and the tension remains slightly larger that the load   through out shortening .Shortening stops when active tension drops to the point where it equals the load. At this point, contraction again becomes isometric. The muscle lengthens (is stretched) when the total tension in the muscle falls below the load.

Since in an isotonic contraction leads to shortening the z lines move closer to each other.

The answer is T