Questions and Answers
What is the contractile unit of a skeletal muscle fibre?
What protein forms the contractile filaments of muscle cells along with myosin?
Actin
What is the charge in electrical potential that occurs during muscle contraction?
Action Potential
Troponin binds to calcium to allow muscle contraction.
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Match the following components with their descriptions:
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The center line of a sarcomere is known as the ______.
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What is formed when myosin attaches to actin?
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What happens to calcium when the nerve impulse stops?
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What triggers the release of acetylcholine in muscle contraction?
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Identify the two contractile proteins involved in skeletal muscle contraction.
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The area where actin myofilaments are not superimposed by myosin myofilaments is known as the ______.
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What is the sliding filament theory?
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Study Notes
Key Concepts of Sliding Filament Theory
- Sarcomere: Basic contractile unit of skeletal muscle, defined as the segment between two Z-lines, containing actin and myosin filaments.
- Actin: Protein that forms thin filaments in muscle cells, attaching directly to the Z-lines.
- Myosin: Fibrous protein that forms thick filaments, with a specific length within a sarcomere known as the A-band.
- Action Potential: Electrical charge change that triggers impulses along muscle and nerve cell membranes.
- Sarcoplasmic Reticulum: Membranous sac system surrounding myofibrils; essential for calcium storage and release during muscle contraction.
- Acetylcholine: Neurotransmitter found throughout the nervous system, responsible for transmitting impulses across the neuromuscular junction.
- Tropomyosin: Protein that wraps around actin, blocking myosin binding sites when the muscle is at rest.
- Troponin: Calcium receptor that, upon calcium binding, moves tropomyosin to expose myosin binding sites on actin.
- Myosin Cross Bridge: Structures on myosin that extend to bind actin filaments, crucial for muscle contraction.
- M-line: Central line of a sarcomere where myosin myofilaments anchor.
- Z-line: Parallel lines defining the boundaries of a sarcomere.
- H-band: Area near the M-line where no actin overlaps with myosin filaments.
- I-band: Region near the Z-line consisting solely of actin, free from myosin overlap.
- A-band: Full length of a myosin filament within a sarcomere.
Process of Muscle Contraction
- Sliding Filament Theory: Explains muscle contraction through actin and myosin filaments sliding past each other, facilitated by cross-bridge formations.
- Muscle Activation: Initiated by a motor nerve impulse that stimulates the sarcoplasmic reticulum to release calcium ions into the muscle cell.
- Muscle Contraction: Calcium binding to troponin allows actin-myosin cross-bridges to form, using ATP for energy to contract and shorten the sarcomere.
- Recharging: ATP is resynthesized to maintain strong binding sites between actin and myosin.
- Relaxation: Occurs when stimulation ceases; calcium is pumped back into the sarcoplasmic reticulum, breaking links between actin and myosin, allowing the muscle to relax.
Requirements for Skeletal Muscle Contraction
- Neural Stimulus: Essential for triggering muscle contraction.
- Calcium Availability: Necessary for the binding of actin and myosin.
- ATP Supply: Provides the energy needed for contraction and relaxation cycles.
Detailed Mechanism of Sliding Filament Theory
- Stimulation by Impulse: Action potential from a motor neuron stimulates muscle fibers, activating the sliding filament mechanism.
- Cross-Bridge Cycling: Myosin heads bind to actin, pulling actin filaments towards the M-line, resulting in sarcomere shortening.
- Role of Troponin and Tropomyosin: Calcium released opens binding sites by displacing tropomyosin, allowing contractions to occur.
Practical Applications
- Drag Flick in Hockey: Illustrates the importance of muscular contractions in sports; requires forceful contractions enabled by the sliding filament theory.
- Understanding Rehab Movements: Recognizes how muscular contractions function during rehabilitation exercises, utilizing concepts of the sliding filament theory.
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Explore the fundamental concepts of the Sliding Filament Theory through effective flashcards. This quiz will help you understand critical terms like sarcomere and actin, which are essential for studying muscle contraction. Enhance your knowledge of functional anatomy in a fun and interactive way.
