What is the ion released from the terminal cisternae that combines with troponin and removes the blocking action of tropomyosin, resulting in the formation of cross bridges?
A
Cl-
B
Na+
C
K+
D
Ca2+
E
H+
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1
Understand the role of the terminal cisternae in muscle contraction. The terminal cisternae are part of the sarcoplasmic reticulum, which stores calcium ions (Ca2+).
Recognize the importance of calcium ions (Ca2+) in muscle contraction. When a muscle fiber is stimulated, Ca2+ is released from the terminal cisternae into the cytosol.
Identify the interaction between Ca2+ and troponin. Ca2+ binds to troponin, a regulatory protein associated with the actin filaments in muscle cells.
Explain how the binding of Ca2+ to troponin affects tropomyosin. This binding causes a conformational change in troponin, which moves tropomyosin away from the myosin-binding sites on actin filaments.
Understand the formation of cross bridges. With tropomyosin moved aside, myosin heads can attach to actin, forming cross bridges, which is essential for muscle contraction.