Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

4. Tissues & Histology

Introduction to Muscle Tissue

Anatomy & Physiology

4. Tissues & Histology

Introduction to Muscle Tissue

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Multiple Choice

When the sarcomere is at rest, which of the following best describes the position of the myosin-binding sites on actin filaments?

They are covered by tropomyosin, preventing cross-bridge formation.

They are degraded by acetylcholinesterase.

They are bound to calcium ions, initiating contraction.

They are exposed, allowing myosin heads to bind freely.

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Verified step by step guidance

Understand the structure of the sarcomere: The sarcomere is the functional unit of muscle contraction, composed of actin (thin filaments) and myosin (thick filaments). Tropomyosin and troponin are regulatory proteins associated with actin filaments.

Learn the role of tropomyosin: Tropomyosin is a protein that covers the myosin-binding sites on actin filaments when the muscle is at rest, preventing the myosin heads from binding to actin and forming cross-bridges.

Understand the role of calcium ions: During muscle contraction, calcium ions bind to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin, exposing them for cross-bridge formation.

Clarify the role of acetylcholinesterase: Acetylcholinesterase is an enzyme that breaks down acetylcholine in the synaptic cleft, terminating the signal for muscle contraction. It does not degrade myosin-binding sites on actin.

Conclude the resting state: When the sarcomere is at rest, the myosin-binding sites on actin filaments are covered by tropomyosin, preventing cross-bridge formation and ensuring the muscle remains relaxed.