Question

Which of the following statements about cardiac muscle is correct? (note: SR = sarcoplasmic reticulum) A)...

Which of the following statements about cardiac muscle is correct? (note: SR = sarcoplasmic reticulum)

A) Sarcolemmal action potentials are conducted into cardiac muscle cells by the Z lines.

B) Ca2+ binds to calmodulin causing tropomyosin repositioning to expose myosin-binding sites.

C) Dihydropyridine receptors bind to RYR receptors allowing Ca2+ release from the SR.

D) RYR receptors in the SR open by Ca2+ -induced Ca2+ release.

Science   Anatomy-And-Physiology   
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Answer #1

C) Dihydropyridine receptors bind to RYR receptors allowing Ca2+ release from the SR.

Explanation : T tubules have a calcium channel called Dihydropyridine receptors (DHPR). In response to muscle depolarizaton DHPR act as voltage sensors and makes physical interaction with another calcium channel present in the sarcoplasmic reticulum called ryanodine receptor (RyR).

This physical interaction between DHPR and RyR releases calcium from sarcoplasmic reticulum which causes muscle contraction.

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