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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1:48 minutes

Problem 20

Textbook Question

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

Verified step by step guidance

Understand the three main types of skeletal muscle fibers: Type I (slow-twitch), Type IIa (fast-twitch oxidative), and Type IIb (fast-twitch glycolytic). Each type has distinct characteristics related to contraction speed, fatigue resistance, and energy metabolism.

Recognize that most muscles are composed of a mixture of these fiber types, rather than a predominance of one type. This mixture allows muscles to perform a variety of functions, such as maintaining posture (Type I fibers) and generating quick, powerful movements (Type II fibers).

Consider the functional demands of specific muscles. For example, postural muscles like the soleus tend to have a higher proportion of Type I fibers, while muscles involved in explosive movements, like the gastrocnemius, may have more Type II fibers. However, even these muscles contain a mix of fiber types.

Understand that the proportion of muscle fiber types can vary between individuals due to genetic factors, training, and activity levels. Athletes specializing in endurance sports may have a higher proportion of Type I fibers, while sprinters may have more Type II fibers.

Conclude that the statement is false because most muscles do not contain a predominance of one skeletal muscle fiber type. Instead, they are composed of a combination of fiber types to support a wide range of activities and functional demands.

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Key Concepts

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

Skeletal Muscle Fiber Types

Skeletal muscles are composed of different types of muscle fibers, primarily classified into Type I (slow-twitch) and Type II (fast-twitch) fibers. Type I fibers are more endurance-oriented, utilizing aerobic metabolism, while Type II fibers are geared towards quick, powerful bursts of activity, relying on anaerobic metabolism. The predominance of one type over the other in a muscle can influence its functional capabilities.

Muscle Fiber Distribution

The distribution of muscle fiber types varies among different muscles in the body and is influenced by genetic factors, training, and the specific functional demands placed on those muscles. For example, muscles used for endurance activities, like the soleus in the calf, tend to have a higher proportion of Type I fibers, while those used for explosive movements, like the quadriceps, may have more Type II fibers. This distribution affects overall muscle performance and adaptability.

Functional Implications

The predominance of a specific muscle fiber type within a muscle has significant implications for its function and performance. Muscles with a higher concentration of Type I fibers are better suited for endurance activities, while those with more Type II fibers excel in strength and power tasks. Understanding this relationship helps in designing training programs tailored to specific athletic goals or rehabilitation needs.

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Related Practice

Textbook Question

The connective tissue covering that encloses the sarcolemma of an individual muscle fiber is called the:

a. Epimysium

b. Perimysium

c. Endomysium

d. Periosteum

A fascicle is a:

a. Muscle

b. Bundle of muscle fibers enclosed by a connective tissue sheath

c. Bundle of myofibrils

d. Group of myofilaments

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

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

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

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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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