Question

The most common type of calcium channels in skeletal muscle are?

• A. T type
• B. L type
• C. R type
• D. N type

Hint:

It is the dihydropyridine receptor sitting in the T-tubule.

Answer 1

The Correct Option is B

Step 1: Skeletal muscle contains a very high density of L-type voltage-gated calcium channels, located mainly in the membrane of the T-tubules. These are the dihydropyridine receptors (DHPRs).

Step 2: In excitation-contraction coupling, depolarisation of the T-tubule causes a voltage-driven conformational change in the L-type channel, which is mechanically coupled to the ryanodine receptor on the sarcoplasmic reticulum, triggering calcium release. So the L-type channel is the key and most abundant channel here.

Step 3: Why the others are wrong: T-type channels are low-voltage-activated and important in pacemaker and neuronal tissue, not the main skeletal muscle channel. N-type and R-type channels are found mainly at nerve terminals and neurons where they trigger neurotransmitter release.

Step 4: Therefore the most common skeletal muscle calcium channel is the L type.