Final answer:
The T-tubules carry the action potential into the cell, triggering the opening of calcium channels in the sarcoplasmic reticulum. This allows Ca to diffuse out and initiate muscle fiber contraction. The arrangement of a T-tubule with the membranes of the SR on either side is called a triad, which surrounds the myofibril containing actin and myosin.
Step-by-step explanation:
The T-tubules carry the action potential into the interior of the cell, triggering the opening of calcium channels in the adjacent sarcoplasmic reticulum (SR) membranes. This allows Ca2+ to diffuse out of the SR and into the sarcoplasm, which initiates muscle fiber contraction by the sarcomeres. The arrangement of a T-tubule with the membranes of the SR on either side is called a triad, which surrounds the myofibril containing actin and myosin.
T-tubules carry the action potential into the interior of the cell, triggering the opening of calcium channels in the adjacent sarcoplasmic reticulum (SR) membranes. This allows Ca2+ to diffuse out of the SR and into the sarcoplasm, which initiates muscle fiber contraction by the sarcomeres.