Answer:
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.
People used vaccines to reduce the risk of infection by working with body as defenses to help them so this vaccines develop immunity to disease
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Well, he grouped them by what they could do (animals that walk, animals that fly, that swim,..) This form of classifying animals is no longer used.
The answer would be solar radiation, the amount of which changes with Earth's tilt, orbital distance from the sun and latitude, temperature, air pressure and the abundance of water.