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

Steps of Muscle Contraction

Anatomy & Physiology

9. Muscle Tissue

Steps of Muscle Contraction

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1:34 minutes

Problem 19c

Textbook Question

When Eric returned from jogging, he was breathing heavily and sweating profusely, and he complained that his legs ached and felt weak. On the basis of what you have learned about muscle energy metabolism, respond to the following questions: c. What metabolic product(s) might account for his sore muscles and his feeling of muscle weakness?

Verified step by step guidance

Understand that during intense physical activity, muscles rely on anaerobic metabolism when oxygen supply is insufficient for aerobic metabolism. This process produces energy quickly but leads to the accumulation of metabolic byproducts.

Recall that anaerobic metabolism primarily involves glycolysis, where glucose is broken down into pyruvate. In the absence of sufficient oxygen, pyruvate is converted into lactic acid (or lactate). This buildup of lactic acid can contribute to muscle soreness and fatigue.

Consider that lactic acid accumulation lowers the pH in muscle cells, leading to acidosis. This acidic environment can interfere with enzyme activity and muscle contraction, contributing to the feeling of weakness and discomfort.

Note that prolonged exercise also depletes energy stores such as ATP and glycogen in muscle cells. The lack of readily available energy can further contribute to muscle fatigue and weakness.

Finally, recognize that sweating profusely during exercise leads to the loss of electrolytes (e.g., sodium, potassium, calcium), which are essential for proper muscle function. Electrolyte imbalance can exacerbate muscle weakness and cramping.

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Key Concepts

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

Lactic Acid Production

During intense exercise, such as jogging, the body may rely on anaerobic metabolism for energy, leading to the production of lactic acid. This occurs when oxygen levels are insufficient for aerobic respiration, causing pyruvate to convert into lactic acid. Accumulation of lactic acid in the muscles can contribute to soreness and fatigue, as it can interfere with muscle contraction and lead to a burning sensation.

Muscle Fatigue

Muscle fatigue is a temporary condition resulting from prolonged physical activity, characterized by a decrease in muscle performance and strength. It can be caused by various factors, including the depletion of energy stores (like glycogen), accumulation of metabolic byproducts (such as lactic acid), and ionic imbalances within muscle cells. This fatigue can manifest as weakness and discomfort in the muscles after strenuous exercise.

Energy Systems in Muscle Metabolism

Muscle energy metabolism involves three primary energy systems: the phosphagen system, anaerobic glycolysis, and aerobic respiration. The phosphagen system provides immediate energy for short bursts of activity, while anaerobic glycolysis kicks in during high-intensity efforts, producing energy quickly but less efficiently. Aerobic respiration is utilized during prolonged, lower-intensity activities. Understanding these systems helps explain how muscles generate energy and the resulting metabolic byproducts during exercise.

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Define neuromuscular junction, motor unit, tetanus, graded response, aerobic respiration, anaerobic glycolysis, muscle fatigue, and neurotransmitter.

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Textbook Question

When Eric returned from jogging, he was breathing heavily and sweating profusely, and he complained that his legs ached and felt weak. On the basis of what you have learned about muscle energy metabolism, respond to the following questions:

a. Why is Eric breathing heavily?

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Textbook Question

b. What ATP-harvesting pathway have his working muscles been using that leads to such a breathing pattern?

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Textbook Question

Smooth muscle has some unique properties, such as low energy usage, and the ability to maintain contraction over long periods. Tie these properties to the function of smooth muscle in the body.

Which of the following is the correct sequence of events for muscle contraction?

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Multiple Choice

Which of the following provides the final 'go signal' for muscle contraction?

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Multiple Choice