What neurotransmitter is released at the neuromuscular junction (NMJ)?

Acetylcholine (ACh) — it binds to nicotinic receptors on the muscle fiber, triggering depolarization.

2. What is the role of calcium (Ca²⁺) in muscle contraction?

Ca²⁺ binds to troponin, causing tropomyosin to shift and expose actin’s binding sites for myosin.

What is excitation-contraction coupling?

The process linking an action potential in the muscle fiber to contraction — involving T-tubules, SR Ca²⁺ release, and cross-bridge cycling.

What happens during the power stroke in muscle contraction?

Myosin heads pull actin filaments toward the center of the sarcomere, powered by ATP hydrolysis.

What is the difference between Type I and Type II muscle fibers?

Type I: Slow-twitch, fatigue-resistant, aerobic. Type II: Fast-twitch, high power, fatigue quickly, anaerobic.

What is the function of the sarcoplasmic reticulum (SR)?

It stores and releases calcium ions that initiate muscle contraction.

What are ligand-gated ion channels?

Channels that open when a chemical messenger (like ACh) binds to them, allowing specific ions to pass and change membrane potential.

What is nitrogen balance, and why is it important?

The comparison of nitrogen intake to nitrogen excretion; it reflects whether the body is gaining (positive) or losing (negative) protein.

What structure conducts action potentials into the muscle fiber interior?

T-tubules — they carry electrical impulses from the sarcolemma deep into the cell.

What happens when Ca²⁺ is pumped back into the SR after contraction?

The muscle relaxes as Ca²⁺ unbinds from troponin, blocking actin’s binding sites again.

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physiology

Question	Answer
What neurotransmitter is released at the neuromuscular junction (NMJ)?	Acetylcholine (ACh) — it binds to nicotinic receptors on the muscle fiber, triggering depolarization.
2. What is the role of calcium (Ca²⁺) in muscle contraction?	Ca²⁺ binds to troponin, causing tropomyosin to shift and expose actin’s binding sites for myosin.
What is excitation-contraction coupling?	The process linking an action potential in the muscle fiber to contraction — involving T-tubules, SR Ca²⁺ release, and cross-bridge cycling.
What happens during the power stroke in muscle contraction?	Myosin heads pull actin filaments toward the center of the sarcomere, powered by ATP hydrolysis.
What is the difference between Type I and Type II muscle fibers?	Type I: Slow-twitch, fatigue-resistant, aerobic. Type II: Fast-twitch, high power, fatigue quickly, anaerobic.
What is the function of the sarcoplasmic reticulum (SR)?	It stores and releases calcium ions that initiate muscle contraction.
What are ligand-gated ion channels?	Channels that open when a chemical messenger (like ACh) binds to them, allowing specific ions to pass and change membrane potential.
What is nitrogen balance, and why is it important?	The comparison of nitrogen intake to nitrogen excretion; it reflects whether the body is gaining (positive) or losing (negative) protein.
What structure conducts action potentials into the muscle fiber interior?	T-tubules — they carry electrical impulses from the sarcolemma deep into the cell.
What happens when Ca²⁺ is pumped back into the SR after contraction?	The muscle relaxes as Ca²⁺ unbinds from troponin, blocking actin’s binding sites again.

Created by: user-1993400

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