muscle physiology

What is the functional unit of a skeletal muscle fiber?

The sarcomere, which is the region delimited by two successive Z lines.

Which regulatory protein blocks the myosin-binding sites on the actin filament during relaxation?

Tropomyosin blocks the binding sites until calcium ions bind to the troponin complex to shift its position.

What is the primary neurotransmitter released by motor neurons at the neuromuscular junction?

Acetylcholine (ACh), which binds to nicotinic receptors on the motor end-plate to trigger depolarization.

Describe the function of the Sarcoplasmic Reticulum (SR) in veterinary muscle physiology.

The SR acts as a Specialized reservoir for calcium ions (Ca^{2+}); upon stimulation, it releases calcium into the sarcoplasm to initiate contraction.

Differentiate between Type I and Type II muscle fibers in animals.

Type I (Slow-twitch/Red) fibers are oxidative, fatigue-resistant, and rich in myoglobin, whereas Type II (Fast-twitch/White) fibers are glycolytic, prone to fatigue, and designed for rapid, powerful movements.