Multiple Choice
In the cross-bridge cycle of muscle contraction, at which stage does ATP hydrolysis occur?
9. Muscle Tissue
Steps of Muscle Contraction
Multiple Choice
What triggers the release of calcium ions from the sarcoplasmic reticulum during muscle contraction?
A
The binding of acetylcholine to receptors on the muscle cell membrane
B
The depolarization of the muscle cell membrane
C
The hydrolysis of ATP by myosin heads
D
The binding of calcium ions to troponin
Verified step by step guidance1
Understand the role of the sarcoplasmic reticulum (SR) in muscle contraction: The SR stores calcium ions (Ca²⁺) and releases them when a muscle cell is stimulated, which is crucial for muscle contraction.
Identify the initial trigger for muscle contraction: The process begins with a nerve impulse that reaches the neuromuscular junction, causing the release of the neurotransmitter acetylcholine.
Explain the role of acetylcholine: Acetylcholine binds to receptors on the muscle cell membrane, leading to the opening of ion channels and an influx of sodium ions (Na⁺), which depolarizes the muscle cell membrane.
Connect depolarization to calcium release: The depolarization of the muscle cell membrane triggers the opening of voltage-gated calcium channels in the sarcoplasmic reticulum, leading to the release of Ca²⁺ into the cytosol.
Clarify the role of calcium ions: The released calcium ions bind to troponin, causing a conformational change that allows myosin heads to bind to actin filaments, ultimately leading to muscle contraction.
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