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Questions and Answers
What structure contains both terminal cisternae and transverse tubule?
What structure contains both terminal cisternae and transverse tubule?
Which component of muscle fiber is primarily responsible for the storage of calcium ions?
Which component of muscle fiber is primarily responsible for the storage of calcium ions?
What is the function of the sarcolemma in muscle fibers?
What is the function of the sarcolemma in muscle fibers?
Which band in a muscle cell appears dark and contains thick myofilaments?
Which band in a muscle cell appears dark and contains thick myofilaments?
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Where are openings into the transverse tubules located in relation to muscle contraction?
Where are openings into the transverse tubules located in relation to muscle contraction?
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What is the primary mode of ATP synthesis during short, intense exercise?
What is the primary mode of ATP synthesis during short, intense exercise?
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Which enzyme is responsible for transferring Pi from one ADP to another?
Which enzyme is responsible for transferring Pi from one ADP to another?
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How is oxygen supplied at the onset of intense exercise?
How is oxygen supplied at the onset of intense exercise?
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What is the role of creatine kinase in ATP synthesis?
What is the role of creatine kinase in ATP synthesis?
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Which of the following is NOT part of the immediate energy pathways?
Which of the following is NOT part of the immediate energy pathways?
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What is the effect of cholinesterase inhibitors on muscle function?
What is the effect of cholinesterase inhibitors on muscle function?
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Which condition is characterized by spastic paralysis?
Which condition is characterized by spastic paralysis?
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What neurotransmitter is crucial at the neuromuscular junction?
What neurotransmitter is crucial at the neuromuscular junction?
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Which event occurs first in the sequence of muscle activation at the neuromuscular junction?
Which event occurs first in the sequence of muscle activation at the neuromuscular junction?
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How does curare affect muscle function?
How does curare affect muscle function?
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What is the consequence of botulism toxin at a neuromuscular junction?
What is the consequence of botulism toxin at a neuromuscular junction?
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What is the key role of glycine in muscle contractions?
What is the key role of glycine in muscle contractions?
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Which of the following describes flaccid paralysis?
Which of the following describes flaccid paralysis?
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What triggers the release of acetylcholine (ACh) at the neuromuscular junction?
What triggers the release of acetylcholine (ACh) at the neuromuscular junction?
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During which phase does a muscle fiber develop tension?
During which phase does a muscle fiber develop tension?
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What is the purpose of excitation–contraction coupling in skeletal muscle contraction?
What is the purpose of excitation–contraction coupling in skeletal muscle contraction?
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What happens during the relaxation phase of a muscle fiber?
What happens during the relaxation phase of a muscle fiber?
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Which component is responsible for increasing calcium concentrations at the NMJ?
Which component is responsible for increasing calcium concentrations at the NMJ?
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Which ion is critical for the exocytosis of ACh from synaptic vesicles?
Which ion is critical for the exocytosis of ACh from synaptic vesicles?
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What initiates the process of muscle contraction?
What initiates the process of muscle contraction?
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What occurs after the motor nerve fiber releases ACh into the synaptic cleft?
What occurs after the motor nerve fiber releases ACh into the synaptic cleft?
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What initiates the contraction of smooth muscle?
What initiates the contraction of smooth muscle?
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Which type of smooth muscle has pacemaker cells that facilitate contraction?
Which type of smooth muscle has pacemaker cells that facilitate contraction?
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What is the role of calmodulin in smooth muscle contraction?
What is the role of calmodulin in smooth muscle contraction?
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Which neurotransmitter has the ability to relax smooth muscle in arteries?
Which neurotransmitter has the ability to relax smooth muscle in arteries?
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What is the primary source of calcium during smooth muscle contraction?
What is the primary source of calcium during smooth muscle contraction?
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What structure in smooth muscle allows it to contract without nervous stimulation?
What structure in smooth muscle allows it to contract without nervous stimulation?
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Which statement best describes the contrasting effects of norepinephrine in smooth muscle?
Which statement best describes the contrasting effects of norepinephrine in smooth muscle?
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What mechanism allows sliding of thin filaments past thick filaments during smooth muscle contraction?
What mechanism allows sliding of thin filaments past thick filaments during smooth muscle contraction?
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Study Notes
Muscle Fiber Components:
- Sarcolemma: Plasma Membrane that encloses the muscle fiber.
- Sarcoplasm: Cytoplasm of the muscle fiber, containing myofibrils.
- Myofibrils: Long protein cylinders that make up muscle fibers.
- Myofilaments: Protein filaments within the myofibrils.
- A band: Dark band of myofibril, containing thick filaments of myosin.
- I band: Light band of myofibril, containing thin filaments of actin.
- Z disc: Attachment point for thin filaments, marking the boundary between sarcomeres.
- Sarcomere: Functional unit of skeletal muscle contraction, region between two Z discs.
- Transverse tubules (T-tubules): Invaginations of the sarcolemma, conduct muscle action potentials.
- Sarcoplasmic reticulum (SR): Network of internal membranes that stores and releases calcium, essential for contraction.
- Triad: A complex of terminal cisternae, T-tubule, and terminal cisternae.
- Terminal cisternae: Enlarged regions of the sarcoplasmic reticulum, store calcium ions.
Neuromuscular Junction:
- Synaptic knob: Enlarged ending of a motor neuron, containing neurotransmitters.
- Synaptic vesicles: Sacs within the synaptic knob containing acetylcholine (ACh).
- Synaptic cleft: Space between the synaptic knob and muscle fiber, where ACh diffuses.
- ACh receptors: On the sarcolemma, bind to ACh to initiate muscle contraction.
- Cholinesterase inhibitors: Substances that inhibit the enzyme acetylcholinesterase, preventing the breakdown of ACh.
- Tetanus toxin: Blocks the release of glycine, a neurotransmitter that inhibits muscle contractions.
- Curare: Competes with ACh for receptors, causing flaccid paralysis.
- Botulism toxin: Blocks the release of ACh, causing flaccid paralysis.
Contraction and Relaxation:
- Excitation: Conversion of a nerve impulse into a muscle impulse.
- Excitation-contraction coupling: The series of events that link the muscle action potential to the sliding of myofilaments.
- Contraction: The muscle fiber shortens and develops tension.
- Relaxation: The muscle fiber returns to its resting length.
Energy Sources for Muscle Contraction:
- Phosphagen system: Short-term energy source that utilizes creatine phosphate to rapidly produce ATP.
- Glycogen-lactic acid system (anaerobic fermentation): Produces ATP for short-term, intense exercise.
- Aerobic respiration: Uses oxygen to produce ATP for sustained, moderate activity.
Smooth Muscle:
- Involuntary: Contracts without conscious control.
- Can contract in response to:
- Chemical stimuli (hormones, carbon dioxide, low pH, oxygen deficiency)
- Stretch
- Pacemaker cells
- Innervated by autonomic nerve fibers: Stimulates contraction with acetylcholine or norepinephrine.
- Contraction is triggered by calcium: Enters from the extracellular fluid (ECF) or the sarcoplasmic reticulum (SR).
- Ca2+ binds to calmodulin: Activates myosin light-chain kinase, which phosphorylates myosin.
- Myosin ATPase hydrolyzes ATP: Enables myosin's power stroke, pulling actin filaments.
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Description
Test your knowledge on the key components of muscle fibers, including structures like sarcolemma, sarcoplasm, and myofibrils. This quiz covers essential terms and their functions that are vital for understanding muscle contraction. Perfect for students studying anatomy or physiology.
