Muscle-relaxing drugs are administered to a patient during major surgery. Which of the two chemicals described next would be a good skeletal muscle relaxant and why? • Chemical A binds to and blocks ACh receptors of muscle cells. • Chemical B floods the muscle cells' cytoplasm with Ca²⁺.

Verified step by step guidance

1. Identify the role of acetylcholine (ACh) in muscle contraction: ACh is a neurotransmitter that binds to receptors on muscle cells, initiating a series of events that lead to muscle contraction.
2. Consider the effect of Chemical A: By binding to and blocking ACh receptors, Chemical A would prevent ACh from initiating muscle contraction, leading to muscle relaxation.
3. Analyze the role of calcium ions (Ca²⁺) in muscle contraction: Ca²⁺ is crucial for muscle contraction as it binds to troponin, allowing actin and myosin interaction.
4. Evaluate the effect of Chemical B: Flooding the muscle cells with Ca²⁺ would enhance the contraction process, as more Ca²⁺ would facilitate the actin-myosin interaction, leading to muscle contraction rather than relaxation.
5. Conclude which chemical is a better muscle relaxant: Chemical A, by blocking ACh receptors, would effectively prevent muscle contraction, making it a suitable skeletal muscle relaxant.

Key Concepts

Acetylcholine (ACh) Receptors

Acetylcholine receptors are proteins located on the surface of muscle cells that bind to the neurotransmitter acetylcholine. When ACh binds to these receptors, it triggers muscle contraction. Blocking these receptors prevents muscle contraction, making it a key mechanism for muscle relaxants used during surgery.

Calcium Ion (Ca²⁺) Role in Muscle Contraction

Calcium ions play a crucial role in muscle contraction by facilitating the interaction between actin and myosin filaments within muscle fibers. When Ca²⁺ floods the cytoplasm, it initiates contraction. Therefore, a chemical that increases Ca²⁺ levels would promote muscle contraction rather than relaxation.

Mechanism of Muscle Relaxants

Muscle relaxants work by interfering with the neuromuscular transmission or the excitation-contraction coupling process. Effective skeletal muscle relaxants typically block ACh receptors or inhibit the release of ACh, leading to reduced muscle tone and paralysis, which is essential during surgical procedures to prevent involuntary movements.