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

Which of the following correctly describes the initial step in the activation of smooth muscle contraction?

Myosin heads bind to actin filaments without the need for calcium.

ATP is hydrolyzed by actin to initiate contraction.

Troponin binds to calcium, exposing myosin-binding sites on actin.

Calcium ions enter the cytosol from the extracellular fluid and sarcoplasmic reticulum.

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Verified step by step guidance

Understand the role of calcium ions in smooth muscle contraction. Calcium ions are essential for initiating the contraction process by interacting with specific proteins within the muscle cell.

Recognize that smooth muscle contraction does not involve troponin, unlike skeletal muscle. Instead, calcium ions bind to calmodulin, a regulatory protein, to activate the contraction process.

Learn that calcium ions enter the cytosol from two primary sources: the extracellular fluid and the sarcoplasmic reticulum. This influx of calcium is the initial step in the activation of smooth muscle contraction.

Understand that once calcium binds to calmodulin, the calcium-calmodulin complex activates myosin light chain kinase (MLCK), which phosphorylates the myosin heads, enabling them to bind to actin filaments.

Review the importance of ATP in the contraction process. ATP provides the energy required for the myosin heads to perform the power stroke and for subsequent relaxation of the muscle.