• Humans have three types of muscle tissue: smooth, cardiac, and skeletal.
  
  
• All muscle can contract or shorten, regardless of type.
  
  
• Skeletal muscles have levels of organization from the macroscopic to the microscopic.
  
  
• Muscles permit movement and have other functions as well.

1. What are the three types of muscles in the human body?
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2. What are the functions of skeletal muscles?
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3. How do skeletal muscles cause bones to move?
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4. What are the major skeletal muscles in the body?
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• Striated Muscle

Art Labeling Activity

• Attachment of Skeletal Muscles (36.0K)
• Skeletal Muscles (21.0K)

• Following nervous stimulation, a chain of events leads to muscle fiber contraction.
  
  
• Nervous stimulation requires a neuromuscular junction where the stimulus is passed from nerve fiber to muscle fiber.
  
  
• When a muscle fiber contracts, the myofilament myosin breaks down ATP.

1. What are the microscopic levels of structure of a skeletal muscle?
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2. How does contraction of a skeletal muscle come about?
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3. What is the role of ATP in muscle contraction?
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Essential Study Partner

• Muscle Cell Function

Animation Activity

• Action Potential
• Striated Muscle Contraction
• Actin-Myosin Cross-Bridges

Art Quiz

• Muscle Fiber
• Interaction of Thick and Thin Filaments
• Cross-Bridge Cycle in Muscle Contraction

• Laboratory observations have established the basics of whole muscle contraction.
  
  
• In the body, muscles have tone and vary in the strength of contraction.

1. How is the contraction of whole muscles studied in the laboratory?
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2. How is moderate tension, or tone, maintained by skeletal muscles?
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3. What is a motor unit?
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• Muscle Stimulation Pattern

• Cellular respiration, creatine phosphate breakdown, and fermentation are three sources of ATP for muscle contraction.
  
  
• Muscle fibers differ in structure and the way they acquire ATP; therefore, certain type fibers help us perform one sport compared to another.

1. What are the sources of ATP for muscle contraction?
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2. What is the difference between slow twitch and fast twitch muscle fibers and the way they acquire ATP?
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• The Case of Rachael Martin and Lactic Acid

Bioethical Focus

• Steroid Use

• The muscular system works with the other systems of the body to maintain homeostasis.

1. How does the muscular system work with the other systems of the body to maintain homeostasis?
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2. What are several muscular disorders?
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