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Questions and Answers
What is the primary function of antagonistic muscles?
What is the primary function of antagonistic muscles?
Muscles can only contract at a joint if there are opposing muscles present.
Muscles can only contract at a joint if there are opposing muscles present.
True
What is the role of calcium in muscle contraction?
What is the role of calcium in muscle contraction?
Calcium ions trigger the interaction between actin and myosin filaments, allowing muscle contraction.
The two ways skeletal muscle fibers attach to bones are directly to the periosteum and through a ______.
The two ways skeletal muscle fibers attach to bones are directly to the periosteum and through a ______.
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Match the muscle type with its characteristic:
Match the muscle type with its characteristic:
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What holds bundles of myosin filaments in the center of the sarcomeres?
What holds bundles of myosin filaments in the center of the sarcomeres?
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Muscle contraction occurs by myofilaments shortening.
Muscle contraction occurs by myofilaments shortening.
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What are the two types of filaments involved in muscle contraction?
What are the two types of filaments involved in muscle contraction?
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During muscle contraction, thick filaments slide relative to __________ filaments.
During muscle contraction, thick filaments slide relative to __________ filaments.
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Match the structure with its function in muscle contraction:
Match the structure with its function in muscle contraction:
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What happens to the A band during muscle contraction?
What happens to the A band during muscle contraction?
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The hydrolysis of ATP by myosin activates the head for the power stroke.
The hydrolysis of ATP by myosin activates the head for the power stroke.
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What activates the myosin head for the power stroke?
What activates the myosin head for the power stroke?
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Explain what occurs during the cross-bridge cycle.
Explain what occurs during the cross-bridge cycle.
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During the power stroke, ADP and Pi are released from the myosin head.
During the power stroke, ADP and Pi are released from the myosin head.
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What happens to the myosin head after ATP binds to it during the cross-bridge cycle?
What happens to the myosin head after ATP binds to it during the cross-bridge cycle?
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ADP and Pi remain bound to the myosin head during the _____ stroke.
ADP and Pi remain bound to the myosin head during the _____ stroke.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What is the result of the power stroke in the cross-bridge cycle?
What is the result of the power stroke in the cross-bridge cycle?
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The body does not contain ATP during the cross-bridge cycle.
The body does not contain ATP during the cross-bridge cycle.
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What is the smallest subunit of muscle contraction?
What is the smallest subunit of muscle contraction?
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What binds to the myosin head to initiate force generation in muscle contraction?
What binds to the myosin head to initiate force generation in muscle contraction?
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Thick myofilaments are primarily composed of Actin.
Thick myofilaments are primarily composed of Actin.
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What is the function of the sarcoplasmic reticulum?
What is the function of the sarcoplasmic reticulum?
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The _____ consists only of thick myofilaments and has no overlap with thin myofilaments.
The _____ consists only of thick myofilaments and has no overlap with thin myofilaments.
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Match each structure with its description:
Match each structure with its description:
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Which bands in myofibrils consist solely of thin myofilaments?
Which bands in myofibrils consist solely of thin myofilaments?
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Myofibrils exhibit alternating dark and light bands due to the overlap of myofilaments.
Myofibrils exhibit alternating dark and light bands due to the overlap of myofilaments.
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What is the composition of thin myofilaments?
What is the composition of thin myofilaments?
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Skeletal muscle cells are described as _____ because they contain multiple nuclei.
Skeletal muscle cells are described as _____ because they contain multiple nuclei.
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Which structure runs the full length of the sarcomere and is the largest protein in the body?
Which structure runs the full length of the sarcomere and is the largest protein in the body?
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What type of muscle is influenced by the autonomic nervous system and under control in most internal organs?
What type of muscle is influenced by the autonomic nervous system and under control in most internal organs?
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Pacemakers require a nervous signal to function properly.
Pacemakers require a nervous signal to function properly.
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What is the primary function of gap junctions in smooth muscle cells?
What is the primary function of gap junctions in smooth muscle cells?
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The type of potential that spreads through smooth muscle cells is called an ______.
The type of potential that spreads through smooth muscle cells is called an ______.
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Which of the following occurs when smooth muscle cells are stretched?
Which of the following occurs when smooth muscle cells are stretched?
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Match the following components with their functions in muscle contraction:
Match the following components with their functions in muscle contraction:
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The plasma membrane of smooth muscle cells is sensitive to stretch, which plays a key role in digestion.
The plasma membrane of smooth muscle cells is sensitive to stretch, which plays a key role in digestion.
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What is the shape of smooth muscle cells?
What is the shape of smooth muscle cells?
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What prevents myosin heads from binding to actin when a muscle is relaxed?
What prevents myosin heads from binding to actin when a muscle is relaxed?
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Calcium ions (Ca2+) play a role in moving tropomyosin to allow muscle contraction.
Calcium ions (Ca2+) play a role in moving tropomyosin to allow muscle contraction.
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What must happen for the formation of actin-myosin cross-bridges?
What must happen for the formation of actin-myosin cross-bridges?
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In a relaxed state, Ca2+ is sequestered in the ______.
In a relaxed state, Ca2+ is sequestered in the ______.
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What triggers the muscle fiber to contract?
What triggers the muscle fiber to contract?
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High levels of Ca2+ lead to the inhibition of cross-bridge formation.
High levels of Ca2+ lead to the inhibition of cross-bridge formation.
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In low Ca2+ levels, tropomyosin ______ cross-bridge formation.
In low Ca2+ levels, tropomyosin ______ cross-bridge formation.
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Match the following components with their functions:
Match the following components with their functions:
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Study Notes
Musculoskeletal System Overview
- The musculoskeletal system is covered, including muscle contraction, muscle metabolism, and a concept map.
- Learning outcomes include explaining muscle movement at joints, antagonistic muscle function, the sliding filament mechanism, calcium's role in contraction, slow-twitch and fast-twitch muscle fiber differences, and smooth and cardiac muscles.
- Bones in mammals retain internal blood vessels (True).
Muscle Tissue Types
- Smooth muscle is found in blood vessels, stomach, and intestines, and powers rhythmic, involuntary movements.
- Skeletal muscle is voluntary and responsible for movements like walking and talking.
- Cardiac muscle is found in the heart, is interconnected for fast signal transmission, and powers rapid heart contractions.
Skeletal Muscle Movement
- Skeletal muscle fibers attach to bones directly or via tendons.
- The origin of a muscle remains stationary during contraction, while the insertion moves.
- Muscles can be antagonistic, meaning one muscle counters the action of another.
Muscle Contraction
- Each skeletal muscle contains numerous muscle fascicles.
- Muscle fascicles contain many muscle fibers (cells).
- Muscle fibers are composed of myofibrils, which are composed of thick (myosin) and thin (actin) myofilaments.
- Striations are due to the overlapping arrangement of thick and thin myofilaments within myofibrils.
- Myofibrils are made of thin and thick myofilaments.
- The sarcomere is the smallest subunit of muscle contraction.
- Titin runs the full length of the sarcomere.
- Myosin filaments are held in the center of sarcomeres by titin.
Myofibril Structure
- Myofibrils alternate dark and light bands.
- Dark bands (A bands) where thick and thin filaments overlap.
- Light bands (I bands) where thin filaments only occur.
- H zone is where only thick filaments are located.
- Z line is a protein disc that marks the boundaries of a sarcomere.
- M line is the middle of the sarcomere.
Muscle Contraction Process
- Myofilaments slide past each other.
- The muscle contracts when the sarcomeres shorten.
- Myosin cross-bridges bind to actin and slide past.
- The width of the A-band does not change during contraction.
- The sarcomere shortens.
- The H Zone and I band shorten as the filaments slide past one another
Muscle Contraction Regulation
- When a muscle is relaxed, myosin heads are blocked by tropomyosin and cannot bind to actin.
- For contraction to occur, tropomyosin must be moved aside by troponin, facilitated by calcium ion (Ca²⁺) levels.
- In low Ca²⁺ levels, tropomyosin inhibits cross-bridge formation.
- In high Ca²⁺ levels, Ca²⁺ binds to troponin, displacing tropomyosin, allowing actin-myosin cross-bridge formation.
- Ca²⁺ is stored within the sarcoplasmic reticulum.
- Muscle cell depolarization stimulates the release of Ca²⁺ from the sarcoplasmic reticulum (SR)
Muscle Metabolism
- At rest, skeletal muscles primarily derive energy from aerobic respiration of fatty acids.
- During exercise, energy also comes from glycogen and glucose from the blood.
- Energy from cellular respiration is needed to make ATP (for the cross-bridge cycle) and pump Ca²⁺ back into the SR during relaxation.
Types of Muscle Fibers
- Skeletal muscles have different proportions of fast-twitch and slow-twitch fibers depending on their main function.
- Fast-twitch fibers are adapted for rapid power generation and respire anaerobically.
- Slow-twitch fibers sustain action for long periods and maintain tension.
- Eye muscles have a higher proportion of fast-twitch fibers.
- Deep leg muscles have a high proportion of slow-twitch fibers.
Functional Types of Muscle Fibers
- Slow-twitch (Type I) fibers are rich in capillaries, mitochondria, and myoglobin, appear red, and are suited for sustained activities.
- Fast-twitch (Type II) fibers are poor in capillaries, mitochondria, and myoglobin, appear white, use stored glycogen, and are adapted for rapid, powerful movements.
Cardiac Muscle
- Cardiac muscle is striated, smaller than skeletal muscle, and has one nucleus per cell.
- Cardiac muscle cells branch and interdigitate to withstand high pressures.
- Intercalated discs provide mechanical adhesions between cells.
Additional Concepts
- Motor units contain one motor neuron and all the muscle fibers it innervates.
- Motor units allow for graded contraction strength, tailoring force to the task.
- Recruitment is the increase in the number of motor units and their size.
- Muscles can be selectively activated by the nervous system to adjust contraction strength.
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Description
This quiz explores the key concepts of the musculoskeletal system, focusing on muscle contraction and metabolism. Participants will learn about different muscle types, their functions, and the mechanics of movement at joints. Test your knowledge on skeletal, smooth, and cardiac muscles, including their roles and characteristics.
