7. Muscle Fiber Structure: T-Tubules, SR & Triad

What are transverse tubules?

Extensions of sarcolemma

What is the common abbreviation for transverse tubules?

T-tubules

In what anatomical direction do T-tubules run relative to muscle?

Perpendicular

What electrical event do T-tubules propagate into the muscle interior?

Action potentials

What organelle is the sarcoplasmic reticulum an equivalent of?

Smooth ER

What is the common abbreviation for the sarcoplasmic reticulum?

SR

What chemical element is stored in large amounts inside the sarcoplasmic reticulum?

Calcium

What physiological process requires calcium stored in the SR?

Contraction

What are the expanded terminal regions of the sarcoplasmic reticulum called?

Terminal cisternae

What three structures compose a triad?

Two terminal cisternae and a T-tubule

How many terminal cisternae are present in a triad?

Two

What central structure lies between the two terminal cisternae in a triad?

T-tubule