Questions and Answers
What is the most common type of muscle tissue in the body?
What are the functions of skeletal muscle?
- Shapes the body, 2. Gives the ability to move, 3. Manipulate the environment, 4. Produces heat, 5. Maintain body posture and position, 6. Stabilize joints
What are muscle fibers?
Skeletal muscle cells that are long, cylindrical, and have more than one nucleus.
What is the sarcolemma?
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What are myofibrils?
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What are myofilaments made of?
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What slides past each other during muscle contraction?
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What are sarcomeres?
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What are thin filaments primarily composed of?
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What are thick filaments primarily composed of?
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What is a transverse (T) tubule?
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What is a terminal cistern?
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What is the sarcoplasmic reticulum?
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What makes up a triad?
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What is the endomysium?
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What is the perimysium?
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What is a fascicle?
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What is the epimysium?
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What are tendons?
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What are aponeuroses?
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What is an insertion in muscle anatomy?
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What is an origin in muscle anatomy?
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What functions do tendons serve?
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What is a neuromuscular junction?
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What is a motor unit?
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What is the synaptic cleft?
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What characteristics do all muscles share?
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What is the structure of a sarcomere?
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What do myosin heads do?
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What happens as a muscle shortens?
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What sequence of events must occur for a muscle to contract?
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How does a motor neuron stimulate a skeletal muscle fiber?
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What is the generation of an action potential in a skeletal muscle fiber?
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Study Notes
Skeletal Muscle Overview
- Skeletal muscle is the predominant type of muscle tissue in the body.
- Key functions include shaping the body, facilitating movement, manipulating the environment, generating heat, maintaining posture, and stabilizing joints.
Muscle Structure
- Muscle fibers are long, cylindrical cells that contain multiple nuclei.
- The sarcolemma is the plasma membrane surrounding a muscle fiber.
- Myofibrils are rod-shaped organelles that occupy the sarcoplasm, recognizable by alternating light (I) and dark (A) bands that create a striped appearance.
- Myofilaments, composed of actin (thin) and myosin (thick), are the threadlike structures forming myofibrils.
Muscle Contraction
- Myosin heads interact with actin filaments during muscle contraction, allowing them to slide past each other.
- Sarcomeres serve as contractile units, defined between two Z discs.
- During muscle contraction, I bands shorten, the distance between Z discs decreases, H zones vanish, and A bands remain the same length.
Muscle Fiber Components
- Transverse (T) tubules are found at the junction of A and I bands, extending deep into muscle fibers alongside terminal cisterns.
- Terminal cisterns are cross channels of the sarcoplasmic reticulum, which is akin to endoplasmic reticulum in muscle fibers.
- A triad consists of a T tubule and two terminal cisterns.
Connective Tissue Coverings
- Endomysium is the sheath around individual muscle fibers made of areolar connective tissue.
- Perimysium surrounds groups of muscle fibers, forming bundles (fascicles), and consists of collagenous tissue.
- Epimysium encases the entire muscle, enclosing numerous fascicles with dense irregular connective tissue.
Tendons and Aponeuroses
- Tendons connect muscles to bones or other muscles, derived from extensions of the epimysium, having a cord-like structure.
- Aponeuroses are sheet-like extensions of epimysium that also connect muscles to each other or to bones.
Muscle Attachments
- The insertion refers to the movable part of the muscle, while the origin is the fixed attachment.
Neuromuscular Physiology
- Tendons help in durability and conserving space.
- The neuromuscular junction is where a motor neuron connects with a muscle fiber.
- A motor unit consists of one neuron and all muscle fibers it innervates.
- The synaptic cleft is the small gap separating neuron and muscle fiber membranes.
Muscle Characteristics
- All muscle types share properties such as excitability, contractility, extensibility, and elasticity.
Action Potential Generation
- Muscle contraction initiates when a nerve stimulate occurs, leading to an action potential in the sarcolemma.
- The action potential travels along the sarcolemma and requires a rise in intracellular calcium levels for contraction.
- ACh (acetylcholine) is released from the axon terminal into the synaptic cleft, binding to receptors on the sarcolemma and triggering electrical events that lead to contraction.
- The process includes generation of an end plate potential, depolarization (Na influx), and repolarization (K efflux).
Myosin Functionality
- Myosin heads pull on actin filaments, which is crucial for muscle contraction.
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Description
Explore the key concepts of skeletal muscle anatomy with this quiz, focusing on the structure and functions of muscle tissue. Understand how skeletal muscles shape the body, enable movement, and contribute to heat production and posture maintenance.