During the propagation of the excitation wave along the sarcolemma, the action potentials travel down the , stimulating the intracellular release of calcium ions.

T-tubules (transverse tubules)

Explanation:

T-tubules, also known as transverse tubules, are narrow tubes that are continuous with the sarcolemma (i.e., the cell membrane of striated muscle cells). In skeletal/cardiac muscle cells, T-tubules form invaginations of the sarcolemma that contain many ion channels involved in excitation-contraction (e-c) coupling of muscle cells. Thus, transverse tubules function to conduct the action potential from the cell membrane (sarcolemma) to the interior of the muscle cell.

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.