Topics:
Animal Physiology, Animal Refresher
Composition of A-band (Dark Band) in Skeletal Muscle
View Complete Answer & Explanation
Question (English)
Dark band or A-band or Anisotropic band of skeletal muscle is composed of:
- Actin only
- Myosin only
- Both Actin and Myosin ✓ Correct
- Tropomyosin only
Explanation:
Correct Answer: Both Actin and Myosin
The A-band (Anisotropic / Dark band) contains both thick (myosin) and thin (actin) filaments in the overlap region. It appears dark because it refracts light in multiple directions (anisotropic).
Bands at a Glance
- I-band: Actin only → Light
- A-band: Actin + Myosin (overlap) → Dark
- H-zone: Myosin only (center of A-band) → Lighter zone within A-band
Key Exam Fact
During muscle contraction (sliding filament theory):
- The A-band remains constant in length (myosin filaments don't change length).
- The I-band and H-zone decrease as actin slides over myosin.
- The sarcomere shortens, but individual filament lengths remain unchanged.
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
