Anatomy Chapter 10 – Flashcards
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fascicles
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bundles of muscle fibers
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epimysium
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Connective tissue layer surrounding an individual muscle. Dense irregular.
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perimysium
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Connective tissue surrounding a fascicle. Dense irregular
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endomysium
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Connective tissue surrounding a muscle fiber. Areolar.
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deep fascia
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an expansive sheet of dense irregular connective tissue that separates individual muscles, binds together muscles with similar functions, and forms sheaths to help distribute nerves, blood vessels, and lymphatic vessels, and to fill spaces between muscles. Also called visceral or muscular fascia.
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superficial fascia
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also called subcutaneous layer, composed of areolar and adipose connective tissue that separates muscle from skin.
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aponeurosis
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a thin, flattened sheet formed by a tendon.
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axon
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nerve fiber. a motor neuron's long extension.
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muscle fiber
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single muscle cell - metabolic activities, contraction
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sarcolemma
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plasma membrane of a muscle fiber - surrounds muscle fiber and regulates entry and exit of materials
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sarcoplasm
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cytoplasm of a muscle fiber - site of metabolic processes for normal muscle fiber activities
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sarcoplasmic reticulum
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smooth endoplasmic reticulum in a muscle fiber - stores calcium ions needed for muscle contraction
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terminal cisternae
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expanded ends of a sarcoplasmic reticulum that are in contact with the transverse tubules - site of calcium ion release to promote muscle contraction
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transverse tubule (T-tubule)
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narrow, tubular extensions of the sarcolemma in to the sarcoplasm, contacting the terminal cisternae; wrapped around myofibrils - quickly transports a muscle impulse from the sarcolemma throughout the entire muscle fiber
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myofibrils
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organized bundles of myofilaments; cylindrical structures as long as the muscle fiber itself - contain myofilaments that are responsible for muscle contraction
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thick filament
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composed of bundles of myosin
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thin filament
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composed of actin, troponin, and tropomyosin
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actin
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double-stranded contractile protein - binding site for myosin to shorten a sarcomere
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tropomyosin
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double-stranded regulatory protein - covers the active sites on actin, preventing myosin from binding to actin when muscle fiber is at rest
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troponin
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regulatory protein that holds tropomyosin in place and anchors to actin - when calcium ions bind to one of its subunits, troponin changes shape, causing the tropomyosin to move off the actin active site, and this permits myosin binding to actin
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titin
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filaments of an elastic protein - help return myofilaments to resting position after contaction; maintain positions of myofilaments in sarcomere
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triad
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a structure made of two terminal cisternae and the centrally placed T-tubule
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myoblasts
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groups of embryonic cells that fuse to form single skeletal muscle fibers
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satellite cells
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embryonic-like cells that remain in skeletal muscle tissue that may be differentiated to aid in repair and regeneration
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myofilaments
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bundles of short myofilaments combine to make myofibrils. bundles are classified as thick or thin filaments
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crossbridges
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formed when myosin heads bind thick filaments to actin in the thin filaments during muscle contraction
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z disc
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a thin transverse protein structure in the center of the i band that serves as an attachment site for thin filament ends.
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sarcomere
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the functional contractile unit of a skeletal muscle fiber. distance between two z discs
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neuromuscular junction
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the point where a motor neuron meets a skeletal muscle fiber
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synaptic knob
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an expanded tip of an axon. when it nears the sarcolemma, it expands further to cover a relatively large surface area of the sarcolemma. a nerve impulse travels through the axon to the synaptic knob
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synaptic vessicles
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small membrane sacs filled with molecules of the neurotransmitter acetylcholine (ACh) located in synaptic knob cytoplasm
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motor end plate
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specialized region of the sarcolemma that has folds and indentations to increase the membrane surface area covered by the synaptic knob.
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synaptic cleft
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narrow space separating the synaptic knob and the motor end plate
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ACh receptors
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in motor end plate, act like doors that normally are closed. ACH is the only "key to open these receptor doors
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acetylcholinesterase (AChE)
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resides in the synaptic cleft, rapidly breaks down molecules of ACh that are released into the synaptic cleft. It is needed so that ACh will not continuously stimulate the muscle.
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motor unit
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composed of a single motor neuron and all of the muscle fibers it controls
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all-or-none principle
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a muscle fiber either contracts completely or does not contract at all.
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Myofibrils
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(smallest) bundles of thick and thin filaments which are covered by sarcoplasmic reticulum.
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Skeletal muscle fibers
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(small) multinucleate, striated, and covered by endomysium.
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Muscle fascicles
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(medium) bundles of muscle fibers which are covered by perimysium.
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muscle trunk
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(big) bundle of fascicles and is covered by epimysium and fascia.
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connective tissue of muscle
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bound firmly to the connective tissue of the tendon.
