Muscle Structure Flashcards

Connective Tissue Structures

• Epimysium: Dense connective tissue layer surrounding an entire muscle, providing structural support and protection.
• Perimysium: Connective tissue that groups muscle fibers into bundles called fascicles, containing blood vessels and nerves.
• Endomysium: Thin connective tissue layer encasing individual muscle fibers, allowing for interaction between muscle cells and nerves.

Muscle Structures

• Tendon: Connective tissue that attaches muscle to bone, transmitting the force generated by muscles during contraction.
• Aponeurosis: Flat sheet of connective tissue that connects muscles to muscles or to other structures, serving a similar role as tendons.
• Muscle Fiber: Basic unit of muscle tissue, long multinucleated cells capable of contraction and force generation.

Cellular Components

• Sarcolemma: Plasma membrane surrounding each muscle fiber, playing a crucial role in muscle contraction by conducting electrical impulses.
• Myofibrils: Rod-like structures within muscle fibers, composed of repeating units called sarcomeres, responsible for muscle contraction.
• Myofilaments: The contractile proteins within myofibrils, divided into thick (myosin) and thin (actin) filaments.

Filament Proteins

• Thin Filaments: Composed primarily of actin, along with regulatory proteins such as tropomyosin and troponin, essential for muscle contraction regulation.

  • Actin: Globular protein that polymerizes to form thin filaments.
  • G Actin: Monomeric form of actin, the building block of filamentous actin.
  • F Actin: Filamentous form of actin, formed from G actin subunits.
  • Tropomyosin: Overlapping protein that covers binding sites on actin in relaxed muscles.
  • Troponin (TnC, TnT, TnI): Complex of three proteins that regulate muscle contraction by binding calcium ions and moving tropomyosin.

• Thick Filaments: Composed mainly of myosin molecules, responsible for generating muscle tension.

  • Myosin: Motor protein with a tail and head structure, functioning as a crossbridge during muscle contraction.
  • Myosin Tail: The elongated tail part of myosin that anchors it within the thick filament.
  • Myosin Head: The globular part of myosin that binds to actin to form crossbridges during contraction.

Neuromuscular Junction Components

• Synaptic Vesicles: Membrane-bound structures within nerve endings that store neurotransmitters, including acetylcholine.
• Synaptic Cleft: The small gap between the presynaptic terminal and the postsynaptic membrane, across which neurotransmitters diffuse.
• Motor End Plate: Specialized region of the muscle fiber plasma membrane that contains receptors for neurotransmitters.

Channels and Proteins

• Voltage Operated Channels: Ion channels that open or close in response to changes in membrane potential, critical for action potential propagation.
• Receptor Operated Channels: Ion channels that open in response to the binding of neurotransmitters, allowing ions to flow in or out.
• Calcium Channels: Specialized channels that allow calcium ions to enter the muscle cells, initiating contraction.
• Ca-ATPase: Enzyme that pumps calcium ions back into the sarcoplasmic reticulum post-contraction, essential for muscle relaxation.

Muscle Fiber Organization

• T Tubules: Extensions of the sarcolemma that penetrate into the muscle fiber, facilitating the rapid transmission of action potentials.
• Terminal Cisternae: Enlarged areas of the sarcoplasmic reticulum adjacent to T tubules, stores calcium ions for muscle contraction.
• Triads: Structural units consisting of a T tubule flanked by two terminal cisternae, important for the regulation of calcium release during muscle contraction.

Sarcomere Structure

• A Band: Dark band in the sarcomere consisting of thick filaments (myosin) and overlapping thin filaments.
• I Band: Light band in the sarcomere containing only thin filaments (actin).
• H Zone: Central region of the A band where thick filaments do not overlap with thin filaments during relaxation.
• M Line: Midpoint of the sarcomere, anchoring thick filaments together.
• Z Line: Boundary between adjacent sarcomeres, anchoring thin filaments and providing structure to the muscle fiber.

Miscellaneous

• Fascicle: A bundle of muscle fibers grouped together, surrounded by perimysium.
• Sarcomere: Functional unit of a muscle fiber, defined as the segment between two Z lines, responsible for muscle contraction mechanics.

Test your knowledge on various muscle structures with this engaging flashcard quiz. Identify terms like epimysium, tendon, and sarcolemma to solidify your understanding of muscular anatomy. Perfect for students of biology or health sciences!