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Questions and Answers
What are the three main types of muscles in the human body?
What are the three main types of muscles in the human body?
Skeletal muscles are responsible for involuntary movements.
Skeletal muscles are responsible for involuntary movements.
False
Smooth muscles are found in the walls of organs and blood vessels.
Smooth muscles are found in the walls of organs and blood vessels.
True
What is the primary function of cardiac muscle?
What is the primary function of cardiac muscle?
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What is the structural and contractile unit of myofibrils?
What is the structural and contractile unit of myofibrils?
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What is the role of ATP in muscle contraction?
What is the role of ATP in muscle contraction?
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The release of calcium ions (Ca2+) into the cytoplasm is essential for muscle contraction.
The release of calcium ions (Ca2+) into the cytoplasm is essential for muscle contraction.
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Which of the following is NOT a property of skeletal muscle?
Which of the following is NOT a property of skeletal muscle?
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The motor unit is composed of a motor neuron and the muscle fibers it innervates.
The motor unit is composed of a motor neuron and the muscle fibers it innervates.
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The neuromuscular junction is the junction between the motor neuron and the muscle fiber.
The neuromuscular junction is the junction between the motor neuron and the muscle fiber.
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What is the role of acetylcholinesterase?
What is the role of acetylcholinesterase?
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Rigor mortis occurs because the myosin cross-bridges cannot detach from actin due to the lack of ATP.
Rigor mortis occurs because the myosin cross-bridges cannot detach from actin due to the lack of ATP.
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Smooth muscle is found in the walls of hollow organs and blood vessels, but not in the heart.
Smooth muscle is found in the walls of hollow organs and blood vessels, but not in the heart.
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What is the difference between thick and thin filaments in smooth muscle compared to skeletal muscle?
What is the difference between thick and thin filaments in smooth muscle compared to skeletal muscle?
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Smooth muscles require ATP for contraction, but not for relaxation.
Smooth muscles require ATP for contraction, but not for relaxation.
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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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Muscle fatigue is a complex phenomenon that can result from metabolic, endocrine, or central factors.
Muscle fatigue is a complex phenomenon that can result from metabolic, endocrine, or central factors.
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The duration and intensity of muscle exercise are the main factors influencing the metabolic component of fatigue.
The duration and intensity of muscle exercise are the main factors influencing the metabolic component of fatigue.
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The endocrine system is not involved in muscle fatigue.
The endocrine system is not involved in muscle fatigue.
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Study Notes
Chapter 2: Muscular Physiology - Skeletal Striated Muscle
- Types of Muscles: Skeletal, smooth, and cardiac muscles.
- Muscle Functions: Movement production, posture maintenance, joint stabilization, heat release.
- Skeletal Striated Muscle (SSM): Experimental study of contraction.
Mechanical Phenomena
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Neuromuscular Junction: Acetylcholine (ACh) release from nerve terminal diffuses across synaptic cleft, and binds to receptors. This triggers a potential action that propagates the along the sarcolemma and T-tubules.
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Calcium Release: The potential action leads to calcium ion release from the terminal cisternae of the sarcoplasmic reticulum.
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Increased Calcium: Results in higher calcium concentration inside sarcoplasm.
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Filament Sliding (Contraction): Increased intracellular Calcium causes myosin heads to bind to actin filaments, creating cross-bridges. The sliding of thin (actin) filaments over thick (myosin) filaments shortens the sarcomere, leading to contraction.
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Contraction Termination: After the action potential ends, increased Calcium is recaptured into the sarcoplasmic reticulum.
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Relaxation (Termination): Calcium levels decrease, myosin releases from actin, and the sarcomere returns to its resting length.
Anatomical Support of Contraction
- Muscle Fiber: Specialized cells adapted for contraction. Elongated shape allows for shortening.
- Mitochondria: Cellular structures required for ATP production (energy for contraction).
- Myofibrils: Contractile units of the muscle fiber, made up of actin and myosin filaments.
- Sarcomere: Structural and contractile unit of myofibrils (fundamental unit of muscle contraction forming the striations).
Muscle Fiber Structure
- Myofibrils: Contain thin actin and thick myosin filaments organized into repeating units (sarcomeres).
- Sliding Filament Theory: The mechanism by which myosin filaments pull on actin filaments to cause contraction.
Contractile Proteins
- Myosin: Thick filaments with myosin heads that bind to actin.
- Actin: Thin filaments that interact with myosin heads to produce movement during contraction.
Excitation-Contraction Coupling
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Molecular Mechanism: Depolarization of sarcolemma propagates through the T-tubules, triggering calcium release from the sarcoplasmic reticulum.
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Energy Source: ATP hydrolysis provides the energy for myosin head movement during muscle contraction. Myosin binds to actin and changes shape pulling the actin filaments towards the center of the sarcomere.
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ATP binding to myosin allows detachment from actin preventing rigor mortis.
Muscle Fatigue
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Metabolic and Peripheral Component: Factors like metabolic changes (glycogen depletion, ion imbalances) and ionic changes affect muscle contractile ability and performance for short high intensity workouts.
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Central Component: Nervous system fatigue reduces peripheral stimulation leading to decreased contraction capabilities. Central nervous system fatigue reduces cortical motor control.
Smooth Muscle
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Structure: Spindle-shaped, single nucleus, fibers found in organs like airways, blood vessels, etc.
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No striations (smooth appearance).
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Contains actin and myosin but not organized in sarcomeres.
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Excitation-Contraction Coupling Mechanism: Similar sliding filament mechanism but differs in regulation. Calcium entry is necessary for contraction, but it’s regulated by different proteins.
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Description
Explore the intricacies of muscular physiology in this quiz focused on skeletal striated muscle. Test your understanding of muscle types, functions, and the mechanical phenomena involved in contraction at the neuromuscular junction. Ideal for students studying human anatomy and physiology.
