Podcast
Questions and Answers
Which of the following is NOT a component of the axial skeleton?
Which of the following is NOT a component of the axial skeleton?
Approximately what percentage of total body weight do skeletal muscles constitute?
Approximately what percentage of total body weight do skeletal muscles constitute?
Which of the following is NOT a primary function of skeletal muscle?
Which of the following is NOT a primary function of skeletal muscle?
What happens to the I-band and H-zone during the sliding filament model of muscle contraction?
What happens to the I-band and H-zone during the sliding filament model of muscle contraction?
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Which two proteins account for approximately 85% of the myofibrillar complex?
Which two proteins account for approximately 85% of the myofibrillar complex?
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A single muscle fiber contains which of the following?
A single muscle fiber contains which of the following?
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Which of the following represents the correct order of muscle structure from largest to smallest?
Which of the following represents the correct order of muscle structure from largest to smallest?
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What is the approximate water content of a muscle fiber?
What is the approximate water content of a muscle fiber?
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Which connective tissue layer directly surrounds individual muscle fibers?
Which connective tissue layer directly surrounds individual muscle fibers?
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What is the function of the connective tissue wrappings within a skeletal muscle?
What is the function of the connective tissue wrappings within a skeletal muscle?
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Upon reaching the sarcolemma, where does the action potential travel next during excitation-contraction coupling?
Upon reaching the sarcolemma, where does the action potential travel next during excitation-contraction coupling?
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Which event directly allows myosin to bind to actin and form a crossbridge?
Which event directly allows myosin to bind to actin and form a crossbridge?
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What is the role of acetylcholinesterase in muscle contraction?
What is the role of acetylcholinesterase in muscle contraction?
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What is a fasciculus?
What is a fasciculus?
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What is the correct order of events in excitation-contraction coupling?
What is the correct order of events in excitation-contraction coupling?
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The epimysium is described as which of the following?
The epimysium is described as which of the following?
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Flashcards
Axial Skeleton
Axial Skeleton
Consists of the skull, vertebral column, ribs, and sternum.
Appendicular Skeleton
Appendicular Skeleton
Includes shoulder girdle, arm bones, pelvic girdle, and leg bones.
Skeletal Muscle Functions
Skeletal Muscle Functions
Produces force for movement, supports posture, aids breathing, and generates heat.
Striated Muscle
Striated Muscle
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Sliding Filament Model
Sliding Filament Model
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Myofilaments
Myofilaments
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Muscle Fiber Structure
Muscle Fiber Structure
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Composition of Muscle Fibers
Composition of Muscle Fibers
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Epimysium
Epimysium
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Perimysium
Perimysium
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Endomysium
Endomysium
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Tendon
Tendon
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Action Potential (AP)
Action Potential (AP)
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Excitation-Contraction Coupling
Excitation-Contraction Coupling
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Power Stroke
Power Stroke
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Study Notes
Muscle Structure & Function
- Skeletal muscles make up 40-50% of total body weight
- The human body contains over 400 skeletal muscles
- Muscles contract, pulling on bony levers to cause movement
- Skeletal muscle functions include force production for locomotion, postural support and breathing, heat production during cold stress, and glucose disposal
Axial vs Appendicular Skeleton
- Axial skeleton: skull, vertebral column (C1-coccyx), ribs, and sternum
- Appendicular skeleton: shoulder girdle, arm bones, wrists, hands, pelvic girdle, leg bones, ankles, and feet
Skeletal Muscle Structure
- Skeletal muscles are composed of cylindrical cells called muscle fibers that lie parallel to each other
- Muscle fibers contain myofibrils that consist of smaller subunits, myofilaments, arranged parallel to the myofibril
- Muscle fiber > fascicle > muscle fiber > myofibril > myofilaments
- Muscle fiber = muscle cell = myocyte = myofiber
Skeletal Muscle Composition
- Water makes up 75% of a skeletal muscle (sarcoplasm)
- Protein (e.g., actin and myosin) accounts for 20%
- Salts and other substances make up 5%
- Myofilaments (actin and myosin) compose ~85% of the myofibrillar complex
- Other proteins perform structural functions or affect protein filament interaction during muscle action. These include tropomyosin, troponin, titin, α-actinin, β-actinin, M protein, and C protein
Fascia Layers
- Muscles have layers of fibrous connective tissue (fascia) wrapping them
- Epimysium is the outer layer of fascia
- Perimysium surrounds fascicles (bundles of fibers)
- Endomysium surrounds individual fibers
Fascia
- Connective tissues in muscles are continuous with tendons
- Tendons interconnect muscles to bones
- Tension in a muscle is transmitted directly to the tendon and bone
Excitation-Contraction Coupling
- Action potential (AP) triggers muscle contraction
- Acetylcholine (Ach) released from axon terminal binds to receptors on the sarcolemma
- AP travels to T-tubules, causing calcium (Ca2+) release from sarcoplasmic reticulum (SR) into the sarcoplasm
- Ca2+ binds to troponin, causing tropomyosin to shift, exposing the myosin binding sites on actin
- Myosin binds to active sites on actin, forming crossbridges and initiating a power stroke, causing sliding of filaments, leading to contraction.
- When stimulation ceases, Ca2+ returns to the SR, tropomyosin shifts back to cover the binding sites, and the muscle relaxes.
Review Questions
- Explain the sliding filament model and how the bands and zones change length during muscle contraction
- Describe the layers of muscle fibers and fascia that surround them
- Understand the steps in excitation-contraction coupling
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Description
Test your knowledge on muscle structure and function in the human body. Explore the differences between axial and appendicular skeletons, and learn about the composition and role of skeletal muscles. This quiz is essential for understanding human anatomy.
