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Questions and Answers
Which type of muscle is voluntary?
Which type of muscle is voluntary?
What is the basic structural and functional unit of a skeletal muscle?
What is the basic structural and functional unit of a skeletal muscle?
Which of the following is not a function of the muscular system?
Which of the following is not a function of the muscular system?
Which muscle type is classified as voluntary?
Which muscle type is classified as voluntary?
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Which of the following definitions correctly describes extensibility?
Which of the following definitions correctly describes extensibility?
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What is the basic functional unit of skeletal muscle?
What is the basic functional unit of skeletal muscle?
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Which of the following is NOT a function of the muscular system?
Which of the following is NOT a function of the muscular system?
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Which structure of the muscle fiber helps with the regulation of intracellular calcium levels?
Which structure of the muscle fiber helps with the regulation of intracellular calcium levels?
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What does the term 'extensibility' refer to in muscle physiology?
What does the term 'extensibility' refer to in muscle physiology?
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Which component of muscles is responsible for facilitating communication between muscle fibers?
Which component of muscles is responsible for facilitating communication between muscle fibers?
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What characteristic primarily distinguishes skeletal muscle from other muscle types?
What characteristic primarily distinguishes skeletal muscle from other muscle types?
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Which structure in muscle fibers is primarily responsible for the regulation of intracellular calcium levels?
Which structure in muscle fibers is primarily responsible for the regulation of intracellular calcium levels?
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Which function does NOT pertain to skeletal muscles?
Which function does NOT pertain to skeletal muscles?
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Which muscle property allows it to respond to stimuli and generate force?
Which muscle property allows it to respond to stimuli and generate force?
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Which of the following definitions describes the ability of muscle to return to its original length after being stretched?
Which of the following definitions describes the ability of muscle to return to its original length after being stretched?
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Among the following, which is a major function of the muscular system linked to communication?
Among the following, which is a major function of the muscular system linked to communication?
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In which way does skeletal muscle contribute to maintaining body temperature?
In which way does skeletal muscle contribute to maintaining body temperature?
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Which type of muscle is not under voluntary control?
Which type of muscle is not under voluntary control?
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What role do skeletal muscles play in respiration?
What role do skeletal muscles play in respiration?
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What is the relationship between skeletal muscles and posture maintenance?
What is the relationship between skeletal muscles and posture maintenance?
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What primary function do skeletal muscles perform to help maintain posture?
What primary function do skeletal muscles perform to help maintain posture?
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How do skeletal muscles contribute to respiration?
How do skeletal muscles contribute to respiration?
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Which function of muscles involves the creation of heat as a by-product?
Which function of muscles involves the creation of heat as a by-product?
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Which type of muscle is responsible for the contraction of the heart?
Which type of muscle is responsible for the contraction of the heart?
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What is contractility defined as in muscle tissue?
What is contractility defined as in muscle tissue?
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Which property of muscle allows it to return to its original shape after being stretched?
Which property of muscle allows it to return to its original shape after being stretched?
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What role do smooth muscles play in the body?
What role do smooth muscles play in the body?
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Which function of the muscular system is involved in all aspects of human interaction?
Which function of the muscular system is involved in all aspects of human interaction?
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What occurs during muscle extensibility?
What occurs during muscle extensibility?
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In terms of muscle function, which of the following is a primary role of skeletal muscle?
In terms of muscle function, which of the following is a primary role of skeletal muscle?
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What is the term for the muscle's ability to return to its original length after being stretched?
What is the term for the muscle's ability to return to its original length after being stretched?
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Which connective tissue surrounds a bundle of muscle fibers known as a fascicle?
Which connective tissue surrounds a bundle of muscle fibers known as a fascicle?
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What structure in a muscle cell is responsible for storing calcium ions?
What structure in a muscle cell is responsible for storing calcium ions?
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Which protein subunit is a key component of thin myofilaments?
Which protein subunit is a key component of thin myofilaments?
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What describes the structure that extends from one Z line to another in a muscle fiber?
What describes the structure that extends from one Z line to another in a muscle fiber?
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Which muscle tissue type is primarily under voluntary control?
Which muscle tissue type is primarily under voluntary control?
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What is the name of the covering that surrounds the entire muscle?
What is the name of the covering that surrounds the entire muscle?
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Which term refers to the capacity of a muscle to be stimulated and contract?
Which term refers to the capacity of a muscle to be stimulated and contract?
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What term is used for the structure that connects muscle to bone?
What term is used for the structure that connects muscle to bone?
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In a sarcomere, which proteins are primarily responsible for contraction?
In a sarcomere, which proteins are primarily responsible for contraction?
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What is the primary role of the presynaptic terminal in muscle contraction?
What is the primary role of the presynaptic terminal in muscle contraction?
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What connects the neuronal axon to the muscle fiber at the neuromuscular junction?
What connects the neuronal axon to the muscle fiber at the neuromuscular junction?
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Which ion's influx is critical for initiating the release of acetylcholine at the neuromuscular junction?
Which ion's influx is critical for initiating the release of acetylcholine at the neuromuscular junction?
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What is the name of the gap that separates the axonal ending and the muscle fiber?
What is the name of the gap that separates the axonal ending and the muscle fiber?
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Which component in the axonal endings contains the neurotransmitter crucial for muscle activation?
Which component in the axonal endings contains the neurotransmitter crucial for muscle activation?
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What primarily occurs at the neuromuscular junction to initiate muscle contraction?
What primarily occurs at the neuromuscular junction to initiate muscle contraction?
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What role does acetylcholine play at the neuromuscular junction?
What role does acetylcholine play at the neuromuscular junction?
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In muscle physiology, what is a primary consequence of the action potential arriving at the presynaptic terminal?
In muscle physiology, what is a primary consequence of the action potential arriving at the presynaptic terminal?
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Which statement accurately describes the role of tropomyosin in muscle contraction?
Which statement accurately describes the role of tropomyosin in muscle contraction?
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What is the primary function of the T tubule in skeletal muscle fibers?
What is the primary function of the T tubule in skeletal muscle fibers?
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During a heavy weight lifting attempt where the weight is immovable, what type of contraction is primarily occurring?
During a heavy weight lifting attempt where the weight is immovable, what type of contraction is primarily occurring?
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Which sequence correctly depicts the events leading to muscle contraction?
Which sequence correctly depicts the events leading to muscle contraction?
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What component of muscle contraction directly binds to an active site on G actin?
What component of muscle contraction directly binds to an active site on G actin?
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What is the primary role of troponin in muscle contraction?
What is the primary role of troponin in muscle contraction?
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Which event is necessary for the initiation of muscle contraction?
Which event is necessary for the initiation of muscle contraction?
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At what age does the loss of muscle fibers begin?
At what age does the loss of muscle fibers begin?
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Which mechanism is NOT involved in muscle fatigue?
Which mechanism is NOT involved in muscle fatigue?
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During muscle relaxation, what happens to calcium in the muscle fiber?
During muscle relaxation, what happens to calcium in the muscle fiber?
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What is the primary cause of muscle soreness after vigorous exercise?
What is the primary cause of muscle soreness after vigorous exercise?
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What distinguishes isometric contractions from isotonic contractions?
What distinguishes isometric contractions from isotonic contractions?
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The hinge region of myosin molecules allows which function?
The hinge region of myosin molecules allows which function?
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What condition is marked by painful spastic contractions of skeletal muscle?
What condition is marked by painful spastic contractions of skeletal muscle?
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What initiates the release of acetylcholine from synaptic vesicles?
What initiates the release of acetylcholine from synaptic vesicles?
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What primarily triggers contraction in skeletal muscle cells?
What primarily triggers contraction in skeletal muscle cells?
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Which of the following statements about Myasthenia Gravis is true?
Which of the following statements about Myasthenia Gravis is true?
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What is the main character of Duchenne Muscular Dystrophy?
What is the main character of Duchenne Muscular Dystrophy?
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What occurs immediately after acetylcholine binds to ligand-gated sodium channels on the motor end plate?
What occurs immediately after acetylcholine binds to ligand-gated sodium channels on the motor end plate?
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What happens during the cessation of action potential along the sarcolemma?
What happens during the cessation of action potential along the sarcolemma?
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Which diagnostic test is appropriate for identifying Duchenne Muscular Dystrophy?
Which diagnostic test is appropriate for identifying Duchenne Muscular Dystrophy?
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What is the function of acetylcholinesterase in the synaptic cleft?
What is the function of acetylcholinesterase in the synaptic cleft?
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What defines an eccentric contraction?
What defines an eccentric contraction?
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What role do the troponin complexes play in muscle contraction?
What role do the troponin complexes play in muscle contraction?
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What role does tropomyosin play in muscle contraction?
What role does tropomyosin play in muscle contraction?
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What causes tendinitis in skeletal muscles?
What causes tendinitis in skeletal muscles?
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What is fibromyalgia primarily characterized by?
What is fibromyalgia primarily characterized by?
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How is choline recycled to the presynaptic terminal?
How is choline recycled to the presynaptic terminal?
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What is a consequence of calcium returning to the sarcoplasmic reticulum?
What is a consequence of calcium returning to the sarcoplasmic reticulum?
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Which component of the muscle contraction process ensures that ligand-gated sodium channels close?
Which component of the muscle contraction process ensures that ligand-gated sodium channels close?
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What triggers the generation of an action potential in a muscle fiber?
What triggers the generation of an action potential in a muscle fiber?
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What is the primary structure that forms the fibrous actin in muscle fibers?
What is the primary structure that forms the fibrous actin in muscle fibers?
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What ensures the tropomyosin does not uncover active sites on actin in a relaxed muscle?
What ensures the tropomyosin does not uncover active sites on actin in a relaxed muscle?
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What happens to acetylcholine after it has fulfilled its role in muscle contraction?
What happens to acetylcholine after it has fulfilled its role in muscle contraction?
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Study Notes
Muscular System Function
- Movement of the Body: Skeletal muscles attached to bones are responsible for movement.
- Maintenance of Posture: Skeletal muscles maintain tone to keep the body upright.
- Respiration: Skeletal muscles in the thorax and diaphragm contract for breathing.
- Production of Body Heat: Skeletal muscle contraction produces heat as a byproduct.
- Communication: Facial muscles and vocal cords enable communication.
- Constriction of Organs and Vessels: Smooth muscle contraction in internal organs and vessels aids in constriction.
- Contraction of the Heart: Cardiac muscle contraction pumps blood throughout the body.
Functional Properties of Muscle Tissue
- Contractility: Muscle tissue's ability to shorten forcefully.
- Excitability: Muscle tissue can be stimulated to contract by a nerve.
- Extensibility: Muscle tissue's ability to stretch beyond its normal resting length and still contract.
- Elasticity: Muscle tissue has the ability to return to its original resting length after being stretched.
Neuromuscular Junction
- The neuromuscular junction is where a nerve stimulates a muscle cell.
- It is formed by the axonal endings and the motor end plate.
Axonal Endings
- Contain small membranous sacs called synaptic vesicles.
- These vesicles contain acetylcholine.
Motor End Plate
- The muscle plasma membrane in the area of the junction.
- Contains acetylcholine receptors.
Synaptic Cleft
- The space between the axonal endings and muscle fibers.
Muscle Contraction
- Muscle contraction happens at the neuromuscular junction.
- Steps involved:
- Action potential arrives at the presynaptic terminal, opening voltage-gated calcium channels.
- Calcium triggers the release of acetylcholine from synaptic vesicles by exocytosis.
- Acetylcholine diffuses across the synaptic cleft and binds to ligand-gated sodium channels on the motor end plate.
- Sodium enters the muscle fiber, causing depolarization, which can generate an action potential.
- Acetylcholine detaches from the channels, which close.
- Acetylcholinesterase removes acetylcholine from the synaptic cleft.
- Choline is transported back into the presynaptic terminal with sodium.
- Acetylcholine is reformed within the presynaptic terminal.
Actin Myofilament Structure
- Composed of:
- Globular (G) actin: Globular subunits that form fibrous (F) actin.
- Tropomyosin: Covers the active sites on G actin subunits in relaxed muscle.
- Troponin: Anchors to actin, prevents tropomyosin from uncovering active sites, and binds calcium.
Myosin Myofilament Structure
- Composed of myosin molecules:
- Two myosin heavy chains.
- Two myosin heads: Bind to active sites on actin to form cross-bridges, attached to the rod portion by a hinge region, and contain ATPase enzymes.
Excitation-Contraction Coupling
- The link between the electrical component of muscle contraction and the mechanical component.
- Occurs at the triad, where a T tubule and two terminal cisternae of the sarcoplasmic reticulum come together.
- For a skeletal muscle to contract, it must:
- Be stimulated by a nerve ending.
- Have an action potential propagated along its sarcolemma.
- Have an increase in intracellular calcium levels.
Cross-Bridge Movement
- The myosin head binds to an active site on actin to form a cross-bridge.
- The myosin head pivots, pulling the actin filament towards the center of the sarcomere.
- This movement is powered by ATP hydrolysis.
- The cross-bridge detaches, and the cycle repeats as long as calcium is present.
Muscle Relaxation
- Occurs when:
- Acetylcholine is no longer released at the neuromuscular junction.
- The action potential along the sarcolemma stops, halting calcium release.
- Calcium diffuses away from troponin molecules.
- Tropomyosin covers the active sites on G actin.
- Cross-bridge formation ceases.
Types of Muscle Contractions
- Isometric: Muscle does not shorten, tension increases.
- Isotonic: Muscle shortens, tone remains constant throughout the contraction.
- Concentric: Muscle shortens as it contracts.
- Eccentric: Muscle lengthens as it contracts.
Diseases of the Muscular System
-
Aging:
- Muscle atrophy: Age-related reduction in muscle mass and function.
- Loss of muscle fibers starts around 25 years old.
- Surface area of the NMJ and number of motor neurons decreases.
-
Muscle Fatigue:
- Temporary state of reduced work capacity.
- Mechanisms involved: Acidosis, ATP depletion, oxidative stress, and local inflammatory response.
-
Muscle Soreness:
- Occurs after vigorous exercise.
- Caused by inflammatory chemicals in the muscle fibers.
-
Cramps:
- Painful, spastic contractions of skeletal muscle.
- Causes: Dehydration and ion imbalance.
-
Tendonitis:
- Inflammation of a tendon or its attachment point due to overuse.
-
Fibromyalgia:
- Chronic, widespread pain in skeletal muscles with no known cure.
- Chronic muscle pain syndrome.
-
Myasthenia Gravis:
- Autoimmune disease.
- Production of autoantibodies that bind to acetylcholine receptors.
- Diagnostics: Electromyography and identification of autoantibodies.
-
Duchenne Muscular Dystrophy:
- Mutations in the dystrophin gene on the X chromosome.
- Progressive muscle weakness and muscle contractures.
- Slow motor development with progressive weakness and muscle wasting.
- Diagnostics: Serum creatinine, muscle biopsies, and immunohistochemical studies.
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Description
This quiz covers the various functions of the muscular system, including movement, posture maintenance, respiration, and heat production. It also highlights the functional properties of muscle tissue such as contractility, excitability, extensibility, and elasticity. Test your knowledge on how muscles operate within the body!
