Questions and Answers
What characterizes the function of the sarcoplasmic reticulum in muscle fibers?
Which component of a skeletal muscle fiber conducts action potentials to the sarcoplasmic reticulum?
What is the primary protein that makes up thick myofilaments in skeletal muscle?
What is the structure of a myosin molecule composed of?
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Which of the following is NOT a protein found in thin myofilaments?
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How are the different types of muscle tissue primarily classified?
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What is the name of the membrane that surrounds muscle fibers?
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What distinguishes skeletal muscle from other muscle types?
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What is the role of the acetylcholinesterase enzyme in muscle contraction?
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Which ion influx is primarily responsible for depolarizing the sarcolemma?
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What occurs immediately after calcium binds to troponin C (Tn.C)?
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What triggers the contraction of skeletal muscle fibers?
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Which type of muscle tissue is characterized as involuntary and non-striated?
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What happens to the myosin head during muscle contraction?
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What is the function of T-tubules in muscle contraction?
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In which systems is smooth muscle predominantly found?
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What is the role of tropomyosin in muscle contraction?
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Which subunit of troponin inhibits contraction?
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What initiates the release of acetylcholine at the neuromuscular junction?
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In the process of excitation-contraction coupling, what is the second step?
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What is the primary neurotransmitter involved in communication between the nerve and muscle at the neuromuscular junction?
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What happens when calcium ions bind to troponin C during muscle contraction?
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Where is the motor end plate located within the muscle fiber?
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What is one of the main components of the neuromuscular junction?
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Study Notes
Types of Muscle Tissue
- Muscles are classified based on their location, histological structure, and control mechanism.
Skeletal Muscle
- Composed of striated muscle fibers that contain myofibrils and myofilaments.
- Myofibrils consist of thick and thin filaments; thick filaments contain myosin, while thin filaments are made of actin.
- Each muscle fiber is encased in a cell membrane known as the sarcolemma, which conducts action potentials.
- The sarcoplasmic reticulum (sER) stores calcium ions (Ca²⁺).
- T-tubules conduct action potentials from the sarcolemma to the sarcoplasmic reticulum.
Myofilaments Structure
- Thick myofilaments are primarily composed of myosin, featuring a head, tail, and flexible hinge (neck).
- The myosin head has an actin-binding site and an ATP-binding site essential for muscle contraction.
- Thin myofilaments include three proteins: actin, tropomyosin, and troponin.
- Each actin protein has a binding site for myosin.
- Tropomyosin wraps around actin and blocks myosin-binding sites during relaxation.
- Troponin, a multi-subunit protein, regulates contraction by binding Ca²⁺.
Excitation-Contraction Coupling
- Muscle contraction involves two main steps: excitation and contraction.
- The neuromuscular junction is where the nervous system communicates with muscle fibers.
- Nerve endings at the neuromuscular junction release acetylcholine (ACh) in response to action potentials.
- ACh diffuses across the synaptic cleft and binds to receptors on the sarcolemma, triggering muscle fiber depolarization.
Excitation Steps
- Depolarization occurs when Na⁺ enters the muscle fiber, leading to action potential propagation along the sarcolemma and T-tubules.
- This triggers the release of Ca²⁺ from the sarcoplasmic reticulum.
Contraction Steps
- Ca²⁺ binds to troponin C, exposing binding sites on actin for myosin.
- Myosin heads, energized by cleaving ATP, attach to actin, initiating muscle contraction.
- The binding of a new ATP molecule leads to detachment of myosin from actin, resulting in muscle relaxation.
Smooth Muscle
- Characterized as involuntary and non-striated muscle tissue.
- Found in various systems:
- Cardiovascular: located in blood vessels.
- Digestive: forms sphincters in the alimentary canal.
- Respiratory: regulates airway diameter.
- Urinary: forms sphincters for the urinary bladder.
- Reproductive: comprises the male reproductive tract.
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Description
Explore the intricacies of muscle physiology in Chapter 5. This quiz covers the different types of muscle tissues, including their histological structure and control mechanisms. Test your understanding of skeletal, smooth, and cardiac muscles.
