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Questions and Answers
Which functional property of muscles refers to the ability to respond to a stimulus?
What type of muscle is striated and involuntarily controlled, directly associated with the pumping of blood?
Which type of muscle tissue is primarily involved in the contraction of hollow organs and blood vessels?
What is the main connective tissue covering that surrounds individual skeletal muscle fibers?
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What term describes the ability of a muscle to recoil to its original length after being stretched?
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What is the primary role of Ca2+ in muscle contraction?
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Which of the following statements about sarcomeres is correct?
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What are myofibrils primarily composed of?
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What primarily gives skeletal muscle fibers their striated appearance?
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What is the name of the connective tissue covering that surrounds each fascicle?
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What role does tropomyosin play in muscle fibers?
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Which structure serves as an anchor for actin myofilaments within the sarcomere?
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Which structures are formed by the association of T tubules and terminal cisternae?
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What type of proteins primarily compose thick filaments?
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What does the term 'sarcomere' refer to in skeletal muscle anatomy?
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What is the function of troponin in muscle contraction?
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What are the thick filaments in skeletal muscle primarily composed of?
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After birth, how does muscle enlargement primarily occur?
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What structure separates individual sarcomeres within a myofibril?
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Which connective tissue covering surrounds an individual muscle fiber?
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What is the main role of the sarcoplasmic reticulum in muscle fibers?
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Study Notes
Organization of Skeletal Muscle
- Muscle belly: a bundle of muscle fibers
- Fascicle: bundle of muscle fibers
- Muscle fiber (muscle cell) is made up of myofibrils
- Sarcomere: unit of myofibrils, responsible for the striated look
- Myofibrils: structure made of myofilaments
- Myofilaments: protein filaments that make up a sarcomere
- Myosin: thick filament
- Actin: thin filament
Skeletal Muscle Fiber Anatomy
- Muscle fibers contain several hundred nuclei located at its periphery
- Muscle fibers range in length from 1mm to 30 cm
- The number of muscle fibers remains constant after birth
- Muscle enlargement is due to an increase in the size of muscle fibers
- Muscle fibers have an alternating light and dark bands
- These bands give muscle fibers a striated appearance
Connective Tissue Coverings
- Each skeletal muscle is covered by a connective tissue sheath called the epimysium
- Skeletal muscle is subdivided into fascicles
- Each fascicle is surrounded by a connective tissue covering called the perimysium
- Each skeletal muscle cell (fiber) is surrounded by a connective tissue covering called the endomysium
Electrical Component Structures
- Sarcolemma (cell membrane) contains inward folds called transverse tubules (T tubules)
- T tubules extend into the center of the muscle fiber
- T tubules are associated with enlarged portions of the smooth endoplasmic reticulum called the sarcoplasmic reticulum
- Enlarged portions of the sarcoplasmic reticulum are called terminal cisternae
- Two terminal cisternae and a T tubule form a muscle triad
- The sarcoplasmic reticulum contains a high concentration of Ca2+
- Sarcoplasm is the cytoplasm of the muscle fiber
- It contains many bundles of protein filaments
Mechanical Component Structures
- The sarcomere provides for the mechanical aspect of muscle contraction
- Bundles of protein filaments are called myofibrils
- Myofibrils consist of two types of myofilaments: actin (thin filaments) and myosin (thick filaments)
- Actin and myosin are arranged into repeating units called sarcomeres
Sarcomere: The Breakdown
- Sarcomere is the basic structural unit of skeletal muscle
- Z disks anchor actin myofilaments and separate one sarcomere from the next
- A sarcomere extends from one Z disk to the next
Main Protein Filaments
- Thick filaments (myosin) are composed of myosin proteins
- Myosin has a head and a tail
- The myosin head binds to actin
- The myosin tail forms the thick filament
- Thin filaments (actin) are primarily composed of actin proteins
- Actin filaments are intertwined to form a double-stranded helix
- When relaxed, myosin binding sites within actin are blocked by tropomyosin
Myofilament Structure: Actin
- Actin myofilaments (thin) are made up of three components: Actin, Troponin, Tropomyosin
- Troponin has binding sites for Ca2+
- Tropomyosin filaments block the myosin myofilament binding sites on the actin myofilaments
Types of Muscles
- Skeletal muscles are attached to bones, striated, and controlled voluntarily
- Cardiac muscles are located in the heart, striated, and controlled involuntarily
- Smooth muscles are located in blood vessels and hollow organs, non-striated, and controlled involuntarily
The Muscular System
- Functions of the muscular system: Movement, Maintain posture, Respiration, Production of body heat, Communication, Constriction of organs and vessels, Contraction of the heart
Functional Properties of Muscles
- Contractility: ability to shorten forcefully
- Excitability: capacity to respond to a stimulus
- Extensibility: ability to be stretched beyond its normal resting length and contract
- Elasticity: ability to recoil to its original resting length after it has been stretched
Whole Skeletal Muscle Anatomy
- Skeletal muscle (striated muscle) comprises approximately 40% of body weight
- Skeletal muscles are complete organs, composed of muscle, nerve, and connective tissue
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Description
Explore the intricate structure and organization of skeletal muscle, including muscle fibers, fascicles, and connective tissue coverings. This quiz delves into the various components such as myofibrils, sarcomeres, and the roles of myosin and actin. Perfect for students studying human anatomy or physiology.
