Questions and Answers
What is a tendon?
What is the epimysium?
A protective layer of connective tissue that surrounds the muscle.
What do myoblasts do?
Stem cells that fuse to form skeletal muscle during embryonic development.
What is a sarcomere?
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What is the function of titin in the sarcomere?
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A muscle cell is also known as a ______.
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Which filaments are found in the I-band?
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What does the H-zone contain?
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What is the role of the sarcoplasmic reticulum?
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The A-band shortens during muscle contraction.
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What is the function of contractile proteins?
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Study Notes
Tendon
- Connects muscle to bone via fibrous connective tissue.
- Composed of collagen and elastin for tensile strength and elasticity.
- Smaller tendons can withstand greater forces; crucial for injury prevention.
Muscle
- Composed of parallel muscle fibers running in the same direction.
- Rich blood and nerve supply leading to effective oxygenation.
Epimysium
- Connective tissue layer under the fascia that envelops the entire muscle.
Perimysium
- Connective tissue that surrounds bundles of muscle fibers, known as fascicles.
Endomysium
- Connective tissue layer encasing individual muscle fibers.
Fascicles
- Bundles of muscle fibers that produce steady force.
Muscle Fiber
- Individual muscle cell containing multiple nuclei.
- Formed from bundles of myofibrils, measuring 50-100 microns.
Myoblasts
- Embryonic stem cells that fuse to create skeletal muscle.
- Result in multinucleate structures called myotubes, differentiating into muscle fibers.
Myofibril
- Composed of actin and myosin filaments arranged in long bundles.
- Main cellular component, comprising 80% of muscle cell volume.
Sarcomere
- Basic contractile unit of muscle, extending from Z line to Z line.
- Responsible for force generation during muscle contraction, measuring 2.2 microns.
Sarcolemma
- The cell membrane that surrounds a muscle fiber.
Sarcomere Structure
- Key components:
- Z Line: outer boundary.
- M Line: center point.
- I Band: contains thin actin filaments.
- A Band: consists of thick myosin filaments with some overlap with actin.
- H Zone: area containing only myosin filaments.
Myosin
- Thick filament measuring 1.6 microns; essential for muscle contraction.
Actin
- Thin filament measuring 1 micron; plays a vital role in muscle movement.
Structural Proteins
- Help maintain and organize muscle structure. Key proteins include:
- Titin: connects Z line to M line, provides elasticity.
- Z-line proteins (e.g., alpha-actinin) and M-line proteins (e.g., myomesin).
Contractile Proteins
- Generate force during contraction. Main proteins include actin, myosin, tropomyosin, and the troponin complex.
Nebulin
- A structural protein that stabilizes actin filaments and helps regulate their length during muscle development.
Titin
- Large protein connecting M-line to Z-line; provides elasticity and stabilizes myosin.
M-line
- Central region of the sarcomere anchoring myosin filaments.
Cross Section Through Sarcomere
- I-band: shows only thin actin filaments.
- H-band: shows only thick myosin filaments.
- A band: region where both filament types overlap.
Actin:Myosin Interaction
- Maximum force generation occurs with optimal filament overlap; three myosins surround one actin filament.
I-band
- Light band consisting exclusively of thin filaments, shortens during contraction.
A-band
- Dark band dominated by myosin with minor overlap of actin; its length remains unchanged during contraction.
H-zone
- Central area of A-band, only containing myosin filaments, which reduces in size during muscle contraction.
T-tubule
- Transverse tubules that facilitate rapid depolarization of muscle cells via plasma membrane invaginations.
Signaling System
- Involves T-tubules and terminal cisternae for effective muscle contraction signaling.
Terminal Cisternae
- Expanded areas of the sarcoplasmic reticulum, surrounding T-tubules, essential for calcium storage and release.
Sarcoplasmic Reticulum
- Organelles in muscle fibers responsible for calcium storage and release upon motor neuron stimulation.
Triads
- Structural arrangements made by a T-tubule and two terminal cisternae, crucial for efficient signaling within the sarcomere.
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Description
Test your knowledge on the anatomy of muscles and tendons. This quiz covers key concepts such as muscle fiber structure, connective tissue layers, and the role of myoblasts in muscle formation. Perfect for students studying human anatomy or kinesiology!
