Muscle Tissue

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Muscle TissueTypes and characteristics of muscular tissue______________________________________Nerve-Muscle relationshipBehavior of skeletal muscle fibers/whole muscles____________________________________________________________________________

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Introduction to MuscleMovement is a characteristic of living things______________________________________ ______________________________________Types of muscle______________________________________Physiology of skeletal muscle

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Characteristics of Muscle_____________________ (excitability)chemical signals, stretch and electrical changes across the plasma membrane_____________________local electrical change triggers a wave of excitation that travels along the muscle fiber____________________________________Extensibility -- capable of being stretched____________________________________ ____________________________________

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Skeletal Muscle_________________________ attached to bones______________________ as long as 30 cmExhibits alternating light and dark transverse bands or striationsreflects overlapping arrangement of internal contractile proteins

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Muscle Fibers______________________________________________ has tunnel-like infoldings or transverse (T) tubules that penetrate the cellcarry electric current to cell interior

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________________ is filled with ______________ (bundles of myofilaments)glycogen (stored energy) and myoglobin (oxygen)______________________________ = smooth ERnetwork around each myofibrildilated end-sacs (terminal ___________) store calcium

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____________________Made of 200 to 500 ___________________entwined polypeptides (golf clubs)In bundles with heads directed outward around the bundled tails

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Thin FilamentsTwo strands __________________Has a myosin binding siteGroove holds _______________________each blocking 6 or 7 active sites of G actins_______________ (calcium-binding) on each tropomyosin molecule

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Regulatory and Contractile ProteinsMyosin and actin are ________________________________________________________ = regulatory proteinsswitch that starts and stops shortening of muscle cellcontraction activated by release of calcium into sarcoplasm and its binding to troponin, troponin moves tropomyosin off the actin active sites

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Overlap of Thick and Thin Filaments

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Striations = Organization of Filaments________________ unit of contraction; gives striated appearance________________ (regions) alternate with lighter I bands anisotrophic (A) and isotropic (I) stand for the way these regions affect polarized light__________________________________________lighter, central H band area contains no thin filaments__________________________________________bisected by ___________ protein anchoring elastic and thin filamentsfrom one Z disc (Z line) to the next is a sarcomere

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Relaxed and Contracted Sarcomeres________________________________________ ________________________________________ pulling Z discs closer togetherpulls on sarcolemmaNotice neither thick nor thin filaments change length during shorteningTheir overlap changes as sarcomeres shorten

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Motor Units___________________________________ ___________________________________throughout the musclewhen contract together causes weak contraction over wide areaprovides ability to sustain long-term contraction as motor units take turns resting (_____________________)________________________small motor units contain as few as 20 muscle fibers per nerve fibereye muscles________________________gastrocnemius muscle has 1000 fibers per nerve fiber

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Neuromuscular Junctions (Synapse)Connection between nerve fiber and muscle cell__________________________________ stimulates muscle cell Components of synapse (NMJ)synaptic knob is swollen end of nerve fiber (contains ACh)junction region of sarcolemmacontains acetylcholinesterase (breaks down Ach)__________________ gap between nerve and muscle cells

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Neuromuscular Toxins________________ (cholinesterase inhibitors) bind to acetylcholinesterase and prevent it from degrading AChspastic paralysis and possible suffocation___________________________________ ___________________________________blocks glycine release in the spinal cord and causes overstimulation of the muscles_____________________ (limp muscles) due to curare that competes with AChrespiratory arrest

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Electrically Excitable Cells_____________________________________ resting membrane potential due to Na+ outside of cell and K+ and other anions inside of cell________________________________________ ________________________________________Stimulation opens ion gates in membraneion gates open (Na+ rushes into cell and K+ rushes out of cell)quick up-and-down voltage shift = action potentialspreads over cell surface as nerve signal

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Muscle Contraction and RelaxationFour actions involved in this process_______________ = nerve action potentials lead to action potentials in muscle fiberexcitation-contraction coupling = action potentials on the sarcolemma activate myofilaments________________ = shortening of muscle fiber ________________ = return to resting length

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