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Which type of DNA is separate from the nuclear genome?
Which type of DNA is separate from the nuclear genome?
Satellite cells are active in undamaged muscle tissue.
Satellite cells are active in undamaged muscle tissue.
False
What are myofilaments primarily responsible for?
What are myofilaments primarily responsible for?
Contraction of muscle fibers
The thick filaments in muscle contraction are mostly made up of _____.
The thick filaments in muscle contraction are mostly made up of _____.
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Match the following types of cells with their function:
Match the following types of cells with their function:
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What causes the depolarization of the muscle fiber at the neuromuscular junction?
What causes the depolarization of the muscle fiber at the neuromuscular junction?
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The sliding filament theory states that muscle contraction occurs by the shortening of myofibrils only.
The sliding filament theory states that muscle contraction occurs by the shortening of myofibrils only.
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What are the primary contractile proteins found in muscle fibers?
What are the primary contractile proteins found in muscle fibers?
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The _______________ is the short gap between the motor neuron and the muscle fiber.
The _______________ is the short gap between the motor neuron and the muscle fiber.
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Match the following muscle fiber types with their characteristics:
Match the following muscle fiber types with their characteristics:
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What percentage of total body mass do skeletal muscles represent?
What percentage of total body mass do skeletal muscles represent?
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Skeletal muscles are responsible for high energy output during rest.
Skeletal muscles are responsible for high energy output during rest.
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What primary fuels do muscles utilize during exercise?
What primary fuels do muscles utilize during exercise?
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Skeletal muscles function as a biological 'engine' that powers ________, ________, and ________.
Skeletal muscles function as a biological 'engine' that powers ________, ________, and ________.
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Match the muscle fiber characteristics with their descriptions:
Match the muscle fiber characteristics with their descriptions:
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Which of the following statements about muscle adaptability is true?
Which of the following statements about muscle adaptability is true?
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Muscle fibers are multi-cellular structures that span several centimeters.
Muscle fibers are multi-cellular structures that span several centimeters.
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What is the primary waste produced by muscle metabolism during exercise?
What is the primary waste produced by muscle metabolism during exercise?
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What is the primary role of the sarcolemma?
What is the primary role of the sarcolemma?
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The sarcoplasmic reticulum surrounds only the thick filaments within a muscle fiber.
The sarcoplasmic reticulum surrounds only the thick filaments within a muscle fiber.
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What are myofibrils primarily composed of?
What are myofibrils primarily composed of?
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The ________ membrane encapsulates each muscle fiber and is involved in generating action potentials.
The ________ membrane encapsulates each muscle fiber and is involved in generating action potentials.
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What are the two primary types of myofilaments in the sarcomere?
What are the two primary types of myofilaments in the sarcomere?
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Which term describes the functional unit of muscle composed of a motor neuron and the muscle fibers it innervates?
Which term describes the functional unit of muscle composed of a motor neuron and the muscle fibers it innervates?
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Mitochondria are considered the 'power house' of the cell.
Mitochondria are considered the 'power house' of the cell.
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Match the following structures to their functions:
Match the following structures to their functions:
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Fast-twitch muscles are typically more resistant to fatigue than slow-twitch muscles.
Fast-twitch muscles are typically more resistant to fatigue than slow-twitch muscles.
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What is the basic structural and contractile unit of the myofibril?
What is the basic structural and contractile unit of the myofibril?
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The myofilaments generate muscle force at the level of the __________.
The myofilaments generate muscle force at the level of the __________.
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The ________ is a watery medium that fills each muscle fiber and contains dissolved proteins and metabolites.
The ________ is a watery medium that fills each muscle fiber and contains dissolved proteins and metabolites.
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Match the following components with their functions in muscle fibers:
Match the following components with their functions in muscle fibers:
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What happens to muscle fiber composition with endurance training?
What happens to muscle fiber composition with endurance training?
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More myofibrils directly correlate with increased myofibril diameter.
More myofibrils directly correlate with increased myofibril diameter.
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What structural feature connects adjacent sarcomeres?
What structural feature connects adjacent sarcomeres?
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What is the primary function of skeletal muscle?
What is the primary function of skeletal muscle?
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Type I muscle fibers are known for their fast contraction speed.
Type I muscle fibers are known for their fast contraction speed.
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What are the two primary types of muscle fibers discussed?
What are the two primary types of muscle fibers discussed?
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Muscle fibers are organized into __________, which are bundles of muscle fibers.
Muscle fibers are organized into __________, which are bundles of muscle fibers.
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Match the muscle characteristics with their definitions:
Match the muscle characteristics with their definitions:
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Which component of skeletal muscle contracts to produce movement?
Which component of skeletal muscle contracts to produce movement?
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Electrolyte imbalance can contribute to exercise-associated muscle cramps.
Electrolyte imbalance can contribute to exercise-associated muscle cramps.
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The model that describes muscle contraction is known as the __________ model.
The model that describes muscle contraction is known as the __________ model.
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Study Notes
Skeletal Muscle
- Skeletal muscle makes up 40% of total body mass and contributes to 20% of total metabolism.
- It's the body's "furnace" via resting thermogenesis.
- It acts as an important reservoir for water, amino acids, carbohydrates, and fats; its development is highly regulated by age, disease, and training.
- A biological "engine" that powers breathing, pumping, locomotion, and posture with ~40% efficiency.
- Energy requirements at rest are low (10-15 kcal kg-¹ day-¹).
- High energy output during exercise (1.0-1.5 kcal kg-¹ min-¹).
- Muscles can generate high force, speed, or endurance, but not all at the same time.
- Fuel sources include carbohydrates or fats, and waste products are CO2, water, and heat.
Skeletal Muscle Structure and Function
- Skeletal muscles are composed of fascicles, fibers, myofibrils, sarcomeres, filaments, proteins, and amino acids.
- Structural and contractile characteristics.
- Muscle fiber types (slow, fast IIa, fast IIx).
- Functional characteristics of muscle fiber types.
- Muscle actions and speed of muscle action and relaxation.
- Muscle force regulation, relating force to speed and power.
Muscle Fiber Types
- Biochemical and contractile properties of skeletal muscle.
- Slow (Type I) fibers: endurance-oriented.
- Fast (Type IIa and IIx) fibers: speed and power-oriented.
- Fiber types and performance.
Muscle Microstructure
- Figure 8.1 shows the structural organization of skeletal muscle.
- Figure 8.2 depicts the microstructure of skeletal muscle, highlighting sarcomeres, actin, and myosin filaments.
- The organization of skeletal muscle includes: Muscle, Fascicles, Fibers, Myofibrils, Sarcomeres, filaments, proteins, and amino acids.
The Sarcolemma
- A phospholipid membrane that encapsulates muscle fibers, acting as a barrier between cytosol and extracellular space.
- Regulates substrate entry, ion traffic, and controls hormone responses.
- Contains excitable receptors for generating action potentials and has cable-like properties to propagate action potentials.
- Contains t-tubule openings linking it to the sarcoplasmic reticulum (SR).
The Cytosol
- The watery medium inside muscle fibers; essential for maintaining consistent internal environment (temperature, pH, and ionic strength).
- Contains various proteins, metabolites (ATP, ADP, Pi, etc.), signalling molecules, and reducing equivalents.
The Sarcoplasmic Reticulum
- Membranous sleeve surrounding myofibrils that stores and releases calcium ions (Ca2+).
- Calcium release is crucial for muscle contraction.
- T-tubules and terminal cisternae transduce action potentials to trigger calcium release, driving muscle contraction.
Myofibrils
- Myofilaments (primarily myosin and actin) arranged into sarcomeres within muscle fibers to generate muscle force.
- Myofibrils run parallel within the fiber.
- Consisting of many stacked sarcomeres.
The Sarcomere
- The fundamental structural and contractile unit of the myofibril.
- Contains thick and thin filaments (myosin and actin).
- Arrangement between Z-discs; regulated by alpha-actinin.
- The sarcomere shortens during contraction.
The Mitochondria
- The "powerhouse" of the muscle fiber, containing oxidative machinery for ATP production.
- Mitochondrial volume varies with fiber type (slow > fast).
- Location impacts speed of ATP generation
- Important for endurance.
The Nucleus
- Muscle fibers are multinucleated.
- Nuclei contain the muscle's genome.
- Essential for regulating gene expression, repair, and growth.
Satellite Cells
- Muscle stem cells located above the sarcolemma.
- Involved in muscle growth and regeneration through quiescence in healthy muscle.
- Active in strained muscle for growth, repair, and hypertrophy/hyperplasia.
From Structure to Movement
- Filament sliding is the mechanism driving muscle contraction.
- Sarcomere shortening occurs through relative movement of actin and myosin filaments.
- Movement of the myofilaments allows for force generation and overall muscle contraction.
Regulatory Proteins: Troponin C
- Functions as a Ca2+ sensor.
- Binds calcium; acts as a molecular switch.
- Tnl, C and T are components of the troponin system which influences the position of Tropomyosin.
Regulatory Proteins: Tropomyosin
- A cable-like protein dimer that lies in a helical groove of actin.
- Position dynamically influences myosin binding sites.
- "Rocks and rolls" in the groove based on calcium occupancy.
- Blocks myosin binding sites in the absence of calcium.
Neuromuscular Junction
- A specialized junction between a motor neuron and a muscle fiber.
- Acetylcholine release triggers an end-plate potential (EPP) and muscle fiber depolarization.
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Description
This quiz explores the anatomy and physiology of skeletal muscle, emphasizing its composition, energy requirements, and functional characteristics. Understand how skeletal muscles contribute to metabolism, movement, and overall physical performance.
