Question

1) If a drugs is used to block the L-type Ca channel in SKELETAL MUSCLES, does it reduce the contraction-efficiency? And WHY.

2) The following statement is FALSE. Why?

"The length of a skeletal muscle twitch is about 10-100ms."

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About the first question

If the drug blocks the L-type Ca channels and REDUCES the contraction-efficiency,

I seem to understand little Ca will get through. Shouldn't this be enough for in a skeletal muscle? Why?

Answer 1

1. Blocking of L-type calcium channels affects skeletal msucle contraction. L-type channels detects voltage for E-C coupling in skeletal, cardiac and smooth muscles. Though L type calcium channels are not required for calcium entry induced muscle contraction, it merely acts as the a voltage sensor to initiate the contraction process by triggering an allosteric interaction with ryanodine receptor (RyR1) of sarcoplasmic reticulum upon conformation change of L-type channels by depolarization of skeletal muscles. These cascade ultimately leads to calcium release from the SR and subsequent muscle contraction.

2. True.

Skeletal muscle twich can last for 10-100ms though the action potential can lasts 1-2 ms.