Topics:
Animal Physiology, Animal Refresher
Composition of I-band (Light Band) in Skeletal Muscle
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Question (English)
Light band or I-band or Isotropic band of skeletal muscle is composed of:
- Actin only ✓ Correct
- Myosin only
- Both Actin and Myosin
- Tropomyosin only
Explanation:
Correct Answer: Actin only
The I-band (Isotropic / Light band) contains only thin (actin) filaments. It appears light under polarized light because it only refracts light in one direction (isotropic).
Muscle Band Composition Summary
| Band/Zone | Composition | Appearance |
|---|---|---|
| I-band (Isotropic) | Actin (thin filaments) only | Light band |
| A-band (Anisotropic) | Both Actin + Myosin | Dark band |
| H-zone | Myosin (thick filaments) only | Lighter area within A-band |
| M-line | Connects myosin filaments | Center of H-zone |
| Z-line | Anchors actin; boundary of sarcomere | Dense line |
During Muscle Contraction
- I-band shortens (actin slides inward)
- H-zone shortens (actin slides into H-zone)
- A-band length stays constant (myosin filament length 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.
