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Questions and Answers
Muscle tissue, one of the four principal types of tissue, consists chiefly of muscle cells that are highly specialized for:
Muscle tissue, one of the four principal types of tissue, consists chiefly of muscle cells that are highly specialized for:
Which of the following is NOT a type of muscle tissue?
Which of the following is NOT a type of muscle tissue?
Skeletal muscle tissue forms skeletal muscles, organs that also contain each of the following, EXCEPT:
Skeletal muscle tissue forms skeletal muscles, organs that also contain each of the following, EXCEPT:
Each cell in skeletal muscle tissue is a:
Each cell in skeletal muscle tissue is a:
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Skeletal muscles perform each of the following functions, EXCEPT:
Skeletal muscles perform each of the following functions, EXCEPT:
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During development, groups of ______________ fuse together to form individual skeletal muscle fibres.
During development, groups of ______________ fuse together to form individual skeletal muscle fibres.
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What is another name for the cell membrane of a muscle fibre?
What is another name for the cell membrane of a muscle fibre?
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Electrical impulses (action potentials) travel down _____________ into the muscle cells to efficiently trigger muscle fibre contraction.
Electrical impulses (action potentials) travel down _____________ into the muscle cells to efficiently trigger muscle fibre contraction.
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What is the name for the cylindrical structures, which can actively shorten and thus are responsible for skeletal muscle fibre contraction?
What is the name for the cylindrical structures, which can actively shorten and thus are responsible for skeletal muscle fibre contraction?
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Myofibrils consist of bundles of ______________, which are protein filaments composed primarily of thin filaments and thick filaments.
Myofibrils consist of bundles of ______________, which are protein filaments composed primarily of thin filaments and thick filaments.
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The ______________________ is an intracellular membrane complex, containing Ca2+ ions.
The ______________________ is an intracellular membrane complex, containing Ca2+ ions.
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_____________ ions are released into the sarcoplasm on receiving electrical signals.
_____________ ions are released into the sarcoplasm on receiving electrical signals.
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Myofilaments are organized into repeating functional units called _______________________ and interactions between the thick and thin filaments of these functional units are responsible for muscle contraction.
Myofilaments are organized into repeating functional units called _______________________ and interactions between the thick and thin filaments of these functional units are responsible for muscle contraction.
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A sarcomere contains each of the following except:
A sarcomere contains each of the following except:
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Visually, when viewed microscopically, the sarcomeres have a banding pattern of A bands (dark bands) with a ____________ at the centre.
Visually, when viewed microscopically, the sarcomeres have a banding pattern of A bands (dark bands) with a ____________ at the centre.
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The ______________ marks the boundary between adjacent sarcomeres and is attached to thin filaments.
The ______________ marks the boundary between adjacent sarcomeres and is attached to thin filaments.
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In the _________________ thin filaments are situated between the thick filaments and they can slide across each other during contraction.
In the _________________ thin filaments are situated between the thick filaments and they can slide across each other during contraction.
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Strands of the protein ___________, which stretch from one Z line to the next M line, function to keep the thick and thin filaments in proper alignment, helps resist extreme stretching, and returns stretched muscles to resting length.
Strands of the protein ___________, which stretch from one Z line to the next M line, function to keep the thick and thin filaments in proper alignment, helps resist extreme stretching, and returns stretched muscles to resting length.
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A strand of the protein __________________ lies alongside thin filaments (and is attached to the M line), which helps align thin filaments of the sarcomere.
A strand of the protein __________________ lies alongside thin filaments (and is attached to the M line), which helps align thin filaments of the sarcomere.
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Under resting conditions, interaction between thick and thin filaments and thus muscle fibre contraction is prevented by the ___________________ complex.
Under resting conditions, interaction between thick and thin filaments and thus muscle fibre contraction is prevented by the ___________________ complex.
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Muscle fibre contraction involves the interaction of ______________ of the thick filaments with binding sites (active sites) on the thin filaments.
Muscle fibre contraction involves the interaction of ______________ of the thick filaments with binding sites (active sites) on the thin filaments.
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Which strands are part of the thin filament and function to cover active sites thus preventing actin-myosin interaction?
Which strands are part of the thin filament and function to cover active sites thus preventing actin-myosin interaction?
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How many subunits does a troponin molecule have?
How many subunits does a troponin molecule have?
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When a skeletal muscle contracts:
When a skeletal muscle contracts:
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During contraction, thin filaments slide towards the centre of each sarcomere alongside the thick filaments and sliding occurs in every sarcomere along a myofibril, thus the:
During contraction, thin filaments slide towards the centre of each sarcomere alongside the thick filaments and sliding occurs in every sarcomere along a myofibril, thus the:
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The model representing the physical changes that occur, which describes what happens to the sarcomere during contraction is called the:
The model representing the physical changes that occur, which describes what happens to the sarcomere during contraction is called the:
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Normal skeletal muscle contraction only occurs when skeletal muscle fibres are activated by motor neurons resulting in so-called:
Normal skeletal muscle contraction only occurs when skeletal muscle fibres are activated by motor neurons resulting in so-called:
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The first step in muscle contraction is the release of _________ into the sarcoplasm.
The first step in muscle contraction is the release of _________ into the sarcoplasm.
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After release from the sarcoplasmic reticulum, ions then trigger interactions between ___________________________, resulting in muscle fibre contraction.
After release from the sarcoplasmic reticulum, ions then trigger interactions between ___________________________, resulting in muscle fibre contraction.
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Interactions during contraction produce __________________ and consume energy.
Interactions during contraction produce __________________ and consume energy.
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When sarcomeres shorten in a contraction, they _________________ the muscle fibre:
When sarcomeres shorten in a contraction, they _________________ the muscle fibre:
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__________________ produced by an individual muscle fibre, or indeed an entire skeletal muscle, can vary widely and can change moment to moment.
__________________ produced by an individual muscle fibre, or indeed an entire skeletal muscle, can vary widely and can change moment to moment.
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A muscle fibre is either contracting ('on') or relaxed ('off'), this is the ______________________ and when a fibre contracts it does so fully (although it may not shorten fully).
A muscle fibre is either contracting ('on') or relaxed ('off'), this is the ______________________ and when a fibre contracts it does so fully (although it may not shorten fully).
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A single stimulus-contraction-relaxation sequence in a muscle fibre is called a twitch, which can be measured as a:
A single stimulus-contraction-relaxation sequence in a muscle fibre is called a twitch, which can be measured as a:
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Which of the following can NOT be used to describe part of a single twitch:
Which of the following can NOT be used to describe part of a single twitch:
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If a skeletal muscle is stimulated a second time immediately after the relaxation phase has ended, the force will rise; if this happens repeatedly force rises like steps in a staircase, a phenomenon called:
If a skeletal muscle is stimulated a second time immediately after the relaxation phase has ended, the force will rise; if this happens repeatedly force rises like steps in a staircase, a phenomenon called:
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If a second stimulus arrives before the relaxation phase has ended a second, more powerful contraction occurs, which is referred to as:
If a second stimulus arrives before the relaxation phase has ended a second, more powerful contraction occurs, which is referred to as:
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_____________________ is induced in muscle when the stimulation rate is increased so much that the relaxation phase is completely eliminated.
_____________________ is induced in muscle when the stimulation rate is increased so much that the relaxation phase is completely eliminated.
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Which of these is not one of the three major types of skeletal muscle fibre:
Which of these is not one of the three major types of skeletal muscle fibre:
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What is generally considered in terms of power and endurance?
What is generally considered in terms of power and endurance?
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Study Notes
Muscle Tissue and Functions
- Muscle tissue is highly specialized for contraction.
- There are three types of muscle tissue: smooth, cardiac, and skeletal.
- Skeletal muscle tissue forms skeletal muscles which contain connective tissues, nerves, and blood vessels.
- Each skeletal muscle cell is a single muscle fibre.
- Skeletal muscles perform numerous functions including maintenance of posture, guarding entrances and exits, movement of digestive contents, and support of soft tissues.
Muscle Fibre Structure
- Muscle fibres are formed by fusion of myoblasts during development.
- The cell membrane of a muscle fibre is called the sarcolemma.
- Electrical impulses are transmitted through transverse (T) tubules into muscle cells to trigger contraction.
- Myofibrils are cylindrical structures responsible for muscle fibre contraction.
- Myofibrils are composed of myofilaments, which are protein filaments made up of thin and thick filaments.
- The sarcoplasmic reticulum (SR) is an intracellular membrane complex containing Ca2+ ions.
- Calcium (Ca2+) ions are released into the sarcoplasm upon receiving electrical signals.
Sarcomere: The Functional Unit of Muscle Contraction
- Myofilaments are organized into repeating units called sarcomeres, responsible for generating muscle contraction.
- A sarcomere contains thin filaments, thick filaments, proteins that regulate filament generation, and proteins that stabilize filament positions.
- Sarcomeres exhibit a banding pattern when viewed microscopically, with A bands (dark) and an M line at the center.
- The Z line marks the boundary between adjacent sarcomeres and is attached to thin filaments.
- The zone of overlap is the region where thin filaments interdigitate with thick filaments and sliding occurs during contraction.
Protein Structure and Function in Sarcomeres
- Titin is a protein that connects the Z line to the M line, maintaining alignment, resisting stretching, and returning stretched muscles to resting length.
- Nebulin aligns thin filaments within the sarcomere.
- Under resting conditions, the troponin-tropomyosin complex prevents interaction between thick and thin filaments, inhibiting muscle fibre contraction.
Muscle Contraction Mechanisms
- Muscle fibre contraction involves the interaction of myosin heads with binding sites on thin filaments.
- Tropomyosin strands cover active sites on thin filaments, preventing actin-myosin interaction.
- Troponin is a protein with three subunits, and it plays a role in regulating the interaction of tropomyosin with myosin.
- During contraction, thin filaments slide towards the center of each sarcomere, shortening the myofibril.
- The sliding filament theory describes the physical changes that occur within the sarcomere during contraction.
Excitation-Contraction Coupling and Muscle Twitch
- Normal skeletal muscle contraction is initiated by activation from motor neurons, a process called excitation-contraction coupling.
- The initial step in muscle contraction is the release of calcium (Ca2+) ions into the sarcoplasm.
- These ions then trigger interactions between thick and thin filaments, leading to muscle fibre contraction.
- Muscle fibre contractions involve the production of tension and consume ATP.
- A single stimulus-contraction-relaxation sequence in a muscle fibre is called a twitch and can be measured using a myogram.
- A single twitch can be divided into a latent period, contraction phase, and relaxation phase.
Muscle Twitch Summation and Tetanus
- If a skeletal muscle is stimulated repeatedly, the force of contraction increases, a phenomenon known as treppe.
- When a second stimulus arrives before the relaxation phase has ended, a more powerful contraction occurs, known as wave summation or temporal summation.
- Complete tetanus occurs when the stimulation rate is high enough to eliminate the relaxation phase, resulting in a sustained contraction.
Skeletal Muscle Fibre Classification
- There are three major types of skeletal muscle fibres: slow, fast, and intermediate, each with different characteristics regarding power and endurance.
Muscle Performance
- Muscle fibre classification and fatigue are important aspects related to muscle performance.
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Description
This quiz explores the specialized structures and functions of muscle tissue, including the three types: smooth, cardiac, and skeletal. Discover how muscle fibres are formed and how they function in contraction and overall muscle operations. Ideal for students studying human anatomy and physiology.
