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

Introduction to Muscles and Muscle Tissue

Anatomy & Physiology

9. Muscle Tissue

Introduction to Muscles and Muscle Tissue

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Problem L3.3

Textbook Question

Ms. Sanchez was in a motorcycle accident in which she lost the use of her right upper limb muscles due to significant nerve damage. However, when an electrode is inserted into her muscles, they are able to contract. Explain specifically why nerve damage caused her to lose the use of her muscles. Why can they still respond to stimulation from an electrode?

Verified step by step guidance

Understand the role of nerves in muscle contraction: Nerves are responsible for transmitting electrical signals (action potentials) from the central nervous system to muscles. These signals travel along motor neurons and stimulate the release of neurotransmitters, such as acetylcholine, at the neuromuscular junction. This triggers muscle contraction.

Explain the impact of nerve damage: In Ms. Sanchez's case, the nerve damage has disrupted the communication between her central nervous system and the muscles in her right upper limb. Without this communication, her muscles cannot receive the necessary signals to contract voluntarily.

Describe the role of electrodes in muscle stimulation: When an electrode is inserted into her muscles, it bypasses the damaged nerves and directly stimulates the muscle fibers. The electrode generates an electrical current that depolarizes the muscle cell membrane, mimicking the natural action potential that would normally come from the nerves.

Clarify why muscles still respond to electrodes: The muscle fibers themselves are still functional and capable of contracting. The issue lies in the damaged nerves, not the muscles. Since the electrode provides an external source of electrical stimulation, it can directly activate the muscle fibers, causing them to contract.

Summarize the distinction: Ms. Sanchez's inability to use her muscles voluntarily is due to the loss of nerve function, which prevents the transmission of signals from her brain to her muscles. However, the muscles remain intact and can still respond to artificial stimulation, such as that provided by an electrode.

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Key Concepts

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

Nerve Damage and Muscle Function

Nerve damage disrupts the communication between the nervous system and muscles, leading to loss of voluntary control. Motor neurons, which transmit signals from the brain to the muscles, become impaired, preventing the brain's commands from reaching the muscles. This results in muscle weakness or paralysis, as seen in Ms. Sanchez's case.

Electrode Stimulation

Electrodes can stimulate muscles directly by bypassing the damaged nerves. When an electrode is inserted into the muscle, it delivers electrical impulses that cause the muscle fibers to contract. This mechanism allows the muscle to respond even when the nerve supply is compromised, demonstrating that the muscle tissue itself can still function independently of nerve signals.

Muscle Contraction Mechanism

Muscle contraction occurs through the interaction of actin and myosin filaments within muscle fibers. When stimulated, these filaments slide past each other, resulting in contraction. This process can still occur in Ms. Sanchez's muscles when stimulated by an electrode, as the muscle's intrinsic mechanisms remain intact despite the loss of nerve input.

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Related Practice

Textbook Question

Which of the following factors is/are responsible for muscular fatigue?

a. Accumulation of chemicals, including calcium and phosphate ions & increased blood flow to the muscle

b. Decreased availability of oxygen

c. Psychological and environmental factors

d. Depletion of key metabolic fuels, such as creatine phosphate

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

Muscles that require a great deal of precise control will have large motor units.

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Textbook Question

Muscle tone is:

a. The result of voluntary shortening of the muscle.

b. The result of a small amount of involuntary activation of motor units by the nervous system.

c. Abnormal—a person's muscles should be relaxed normally.

d. Present only where there is damage to the nervous system.

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Textbook Question

Some athletes will consume only protein for several days before a competition, which reduces the amount of glycogen in both the muscle fibers and the liver. What effect would this have on their ability to perform activities that require short, powerful bursts of activity? How would it affect their ability to perform endurance activities?

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Textbook Question

What is thought to cause excess postexercise oxygen consumption?

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Textbook Question

List some of the functions of smooth muscle tissue.

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Textbook Question

Which of the following best describes single-unit smooth muscle tissue?