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

9. Muscle Tissue

Structure of a Skeletal Muscle

Anatomy & Physiology

9. Muscle Tissue

Structure of a Skeletal Muscle

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Problem 13

Textbook Question

Which of the following types of muscle fibers have low myosin ATPase activity and are classified as slow-twitch?
a. Type I fibers
b. Type IIa fibers
c. Type IIx fibers
d. Type III fibers

Verified step by step guidance

Understand the classification of muscle fibers: Muscle fibers are categorized into different types based on their contraction speed, metabolic properties, and myosin ATPase activity. The main types are Type I, Type IIa, and Type IIx fibers. Note that Type III fibers are not a recognized category in human muscle physiology.

Recall the characteristics of Type I fibers: These are slow-twitch fibers that have low myosin ATPase activity, meaning they hydrolyze ATP at a slower rate. This contributes to their slower contraction speed. They are highly resistant to fatigue and rely primarily on aerobic metabolism.

Compare with Type II fibers: Type IIa fibers are fast-twitch fibers with intermediate myosin ATPase activity and a mix of aerobic and anaerobic metabolism. Type IIx fibers are also fast-twitch but have high myosin ATPase activity and rely predominantly on anaerobic metabolism. Both are faster and less fatigue-resistant than Type I fibers.

Eliminate incorrect options: Since Type IIa and Type IIx fibers have higher myosin ATPase activity and faster contraction speeds, they do not fit the description of slow-twitch fibers with low myosin ATPase activity. Type III fibers are not a valid category, so they can also be eliminated.

Conclude that Type I fibers are the correct answer: Based on their low myosin ATPase activity, slow contraction speed, and reliance on aerobic metabolism, Type I fibers are classified as slow-twitch fibers.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Muscle Fiber Types

Muscle fibers are categorized into different types based on their physiological and biochemical properties. The primary types are Type I (slow-twitch) and Type II (fast-twitch), with Type II further divided into IIa and IIx. Type I fibers are known for their endurance capabilities, while Type II fibers are more suited for explosive movements.

Slow-Twitch Fibers

Slow-twitch fibers, or Type I fibers, are characterized by their high endurance and low fatigue rates. They have a rich supply of blood vessels and mitochondria, allowing for efficient aerobic metabolism. These fibers are primarily used in activities requiring sustained effort, such as long-distance running.

Myosin ATPase Activity

Myosin ATPase activity refers to the enzyme's ability to hydrolyze ATP, which is crucial for muscle contraction. Fibers with low myosin ATPase activity, like Type I fibers, contract more slowly and are more efficient in using oxygen for energy. In contrast, fast-twitch fibers (Type II) have higher ATPase activity, enabling quicker contractions but less endurance.

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Related Practice

Textbook Question

Thick and thin myofilaments have different compositions. For each descriptive phrase, indicate whether the filament is, a. thick or b. thin.

_____ (1) contains actin

_____ (2) contains ATPases

_____ (3) attaches to the Z disc

_____ (4) contains myosin

_____ (5) contains troponin

_____ (6) does not lie in the I band

The function of the T tubules in muscle contraction is to:

a. Make and store glycogen

b. Release Ca²⁺ into the cell interior and then pick it up again

c. Transmit the action potential deep into the muscle cells

d. Form proteins

True or false: Most muscles contain a predominance of one skeletal muscle fiber type. Explain the reasoning behind your choice.

The primary action of the biceps brachii muscle of the anterior arm is to flex the forearm at the elbow. However, when this muscle is inflamed, pain is felt in the shoulder. Explain this finding.

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Textbook Question

Mr. Nasheed has cerebral palsy and suffers severe skeletal muscle spasms as a result of his condition. He is prescribed the drug dantrolene, which prevents the release of Ca²⁺ from the SR. Explain how this will treat his muscle spasms.

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Textbook Question

Michael had a nervous habit of chewing on the inner lining of his lip with his front teeth. The lip grew thicker and thicker from years of continual irritation. Michael's dentist noticed his greatly thickened lip, then told him to have it checked to see if the thickening was a tumor. A biopsy revealed hyperplasia, but no evidence of neoplasia. What do these terms mean? Did Michael have cancer of the mouth?

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Textbook Question

Why are the connective tissue wrappings of skeletal muscles important? Name these connective tissue coverings, beginning with the finest and ending with the coarsest.

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Textbook Question

Why are the connective tissue wrappings of skeletal muscles important? Name these connective tissue coverings, beginning with the finest and ending with the coarsest.

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Which of the following types of muscle fibers have low myosin ATPase activity and are classified as slow-twitch?a. Type I fibersb. Type IIa fibersc. Type IIx fibersd. Type III fibers

Key Concepts

Muscle Fiber Types

Slow-Twitch Fibers

Myosin ATPase Activity

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Which of the following types of muscle fibers have low myosin ATPase activity and are classified as slow-twitch?
a. Type I fibers
b. Type IIa fibers
c. Type IIx fibers
d. Type III fibers