Muscular System I: Skeletal Muscle Tissue and Muscle Organization
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| 3 types of muscle tissue | skeletal, cardiac, smooth
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| skeletal muscle attaches to | skeleton
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| skeletal muscles have...very...and... | single...long...cylindrical striated cells
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| skeletal muscle | multinucleate (peripherally located)
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| skeletal muscle can be controlled | voluntarily
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| cardiac muscle occurs in the | heart wall
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| cardiac muscle has branching chains of | striated cells
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| cardiac muscle has one | nucleus per cell; some can be binucleate
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| intercalated discs of cardiac muscle contain | several types of cell junctions
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| cardiac cells are | electrically coupled by gap junctions
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| cardiac muscles are controlled | involuntarily
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| smooth muscle occurs chiefly in | walls of hollow organs
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| smooth muscle has what type of cells | single, fusiform nonstriated cells
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| smooth muscle cells are | uninucleate
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| smooth muscle is controlled | involutnarily
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| 3 types of tissues share | 4 specialized properties
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| 4 specialized properties | excitability, contractility, elasticity, extensibility
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| excitability is the ability of a muslce cell to respond to | nerve signals or other stimuli, causing electrical impulses to travel along the muscle plasma membrane
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| contractility is the ability to generate a strong | pulling force while muscle cells shorten or contract
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| elasticity is the ability of a muscle after being stretched, to | recoil passively to its original or resting length
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| extensibility is the ability to continue to | contract over a range of resting lengths
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| skeletal muscle tissue produces | movement
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| skeletal muscle tissue maintains | posture and body position
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| skeletal muscle tissue supports | soft tissue
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| skeletal muscle tissue regulates | entrance and exit of materials
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| skeletal muscle tissue generates | heat through muscle contractions to maintain body temperature
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| skeletal muscle tissue stabilizes | joints
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| skeletal muscles is surrounded by...and is comprised of | epimysium...bundles of muscle fascicles
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| muscle fascicle is a group or bundle of | muscle fibers surrounded by a perimysium
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| muscle fiber (myofiber or muscle cells) | a highly elongated cell comprised of myofibrils surrounded by endomysium
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| sarcolemma (skeletal) | plasma membrane of muscle fiber which is comprised of abundant myofibrils
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| sarcoplasm | cytoplasm of muscle fiber which contains numerous myofibirls
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| myofibril is a cylindrical structure which is as | long as the entire cell and consists of sarcomeres; surrounded by sarcoplasmic reticulum
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| myofibrils can...and are | shorten...responsible for contraction of the skeletal muscles fiber
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| myofibril contraction leads to | shortening the entire cell bec. a myofibiril is attached to the sarcolemma at each end of the cell
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| sarcoplasmic reticulum (SR) | internal membrane complex that is similar to the SER of other cells
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| the SR is closely associated with | the transverse tubules (T)
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| SR plays important role in | controlling the contraction of individual myofibrils via the release of calcium ions
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| transverse (T) tubules | deep invaginations of the sarcolemma which allow electrical impulses to quickly travel to the interior of the cell
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| terminal cisternae | expanded chambers on either side of a transverse tubule where the tubule of the SR has enlarged and fused
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| triad | combination of a pair of terminal cisternae plus a transverse tubule
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| sarcomere | myofibrils consist of sarcomeres, which are repeating units of myofilaments; smallest functional units of muscle fibers
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| myofilaments | sarcoplasm of muscle contains protein filaments, which generate contractile force
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| myofilaments determine the | striation pattern in skeletal muscle fibers
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| myofilaments fill most of the | sarcoplasm of each musle fiber (cytoplasm)
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| myofilaments are organized in the | repeating units called sarcomeres
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| 2 primary types of myofilaments in muscle cells | actin and myosin
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| actin | protein filaments found in thin filaments
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| myosin | protein filaments found in thick filaments
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| the striated apperance of skeletal muscle tissue arises from the | organization of the thick and thin filaments within the myofibrils of the sarcomere
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| myofibrils are arranged | parallel to the long axis of teh cell, with their sarcomeres arranged side to side
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| myofibrils of the sacromere give the apperance of | distinct dark and light bands
(striations correspond to these bands of the individual sarcomeres)
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| m line | group of proteins which link the thick filaments that lie in the center of the sarcomere
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| z lines or z discs are open | meschworks of interconnecting proteins called actinins, which occur where thin filaments from adjacent sarcomeres join
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| thin filaments are attached to the | z lilne and extend toward the m line
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| zone of overlap | area where the thin filaments pass between the thick filaments
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| in a 3-D cross-sectional view each thin filament is surrounded by | 3 thick filaments arranged in a triangle, while 6 thin filaments surround each thick filament
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| a band | area containing thick filaments, including the m line, the h band, and the zone of overlap; appears as a "dark band"
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| h band is the area | containing thick filaments only
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| i band | the area containing thin filaments only, appears as a "light band"
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| during contraction, the z lines/discs move | closer together, and the I bands and H bands shorten
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| memory aid | A bands are dArk, I bands are lIght (anisotropic characteristics and isotropic characteristics respectively)
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| thin filaments | F actin, nebulin, G actin, tropomyosin, troponin
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| F actin | strand of 300-400 globular G actin molecules
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| nebulin | slender strand of proteins that holds the F actin strand together
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| G actin molecules contains an | active site that can bind to a thick filament, in the same manner that a substrate molecule binds to an enzyme's active site
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| tropomyosin: protein molecules that | form a long chain, which covers the active sites, preventing actin-myosin interaction
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| troponin | protein molecules that hold the tropomyosin strand in place
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| troponin changes position to | move the tropomyosin molecule, exposing the active site prior to a muscle contraction
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| troponin acts as the | regulator molecule of a muscle contraction
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| thick filaments | myosin, proteins of M line, cross bridges, titin
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| approximately how many myosin molecules comprise the thick filament? | 500
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| each myosin molecule consists of a | double myosin strand with an attached, elongate tail and a free globular head
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| proteions of the m line interconnect | adjacent thick filaments, midway along their length
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| myosin heads are also known as | cross-bridges bec they connect thick filaments and thin filaments during a muscle contraction
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| myosin heads project | outward toward the surrounding thin filaments, as the entire myosin molecules are oriented away from the M line
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| titin | protein molecule that makes up the core of each thick filament
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| a strand of titin extends the | length of the filament and attaches the M line to the Z line
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| an exposed portion within the I band is | highly elastic and will recoil after stretching
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| titin is completely | relaxed in the normal resting sarcomere
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| titin becomes tense only | when some external force stretches the sarcomere
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| when sarcomere of titin is stretched the titin strands help | maintain the normal alignment of the thick and thin filaments
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| when the stretching force is removed, titin fibers help | return the sarcomere to its normal resting length
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| shapes of skeletal muscle | spindle-shaped cylinders, triangles, sheets
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| each skeletal muscle is an...and contains | organ...tissue elements, blood vessels and nerves, as well as being comprised mostly of muscle fiberss
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| organization levels in a skeletal muscle | whole muscle - fascicle - fiber - myofibril - sarcomere - myofilament (actin and myosin)
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| connective tissue elements | epimysium, perimysium, endomysium
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| epimysium | DICT sheath wrapped around a whole muscle
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| perimysium | fibrous CT sheath around a fascicle
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| endomysium | thin reticular fiber CT sheath around each muscle fiber
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| every skeletal muscle fiber is | innervated and stimulated by a nerve cell to contract
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| every skeletal muscle fiber has a | rich blood supply and has fine nerve fibers and capillaries in the endomysium
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| origin of skeletal muscle | immovable attachment from which a muscle extends
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| insertion of skeletal muscle | more movable attachment
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| skeletal muscles attach to bones through | tendons, aponeuroses or direct attachments
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| skeletal muscle contraction exerts a | pull, or tension, and shortens the muscle fiber in length
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| the skeletal muscles attach to the | skeleton in a way that keeps them at a near-optimal length for generating maximum contractile forces
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| muscle contraction is accurate for | muscles involved in activities such as walking where the muscles contract and relax repeatedly
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| muscle fibers(skeletal) are stretched to | near optinmal length before stimulation of contraction occurs
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| the presence of | calcium ions is the trigger for a contraction in skeletal muscle
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| the presence of | ATP is required for the contraction to occur
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| sliding filament theory or mechanism explains the | physical changes that occur between the thin and thick filaments during muscle contraction
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| the h band and i band get...with the sliding filament theory | smaller
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| the zone of overlap gets...with sliding filament theory | larger
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| the z lines move...with sliding filament theory | closer
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| the width of the a band ...during sliding filament theory | remains constant throughout the contraction
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| mechanism steps of the sliding filament theory 1) | myosin heads of thick filaments bind to active sites on thin filaments, causing sliding to occur
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| step 2) | cross-bridge binding; myosin head pivots toward the m line, pulling the thin filament toward the center of the sarcomere
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| step 3) | cross bridge then detaches and returns to irs original position and is ready for the next cycle of "bind, pivot, detach, return" regarding its original position
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| step 4) | z lines move toward the m line when the thick filaments pull on the thin filaments, causing the sarcomere to shorten
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| when a nerve cell stimulates a muscle fiber, it sets up an | impulse in the sarcolemma that signals the sarcoplasmic reticulum to release calcium ions
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| the release of calcium ions then initiates the | sliding of the myofilaments (translates to muscle contraction)
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| motor neurons innervate individual skeletal muscle fibers at | neuromuscular synapses or junctions (motor end plates)
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| neuromuscular synapse is a specific synapse between | a motor neuron and a muscle cell
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| synaptic terminal is the expanded tip of the | motor neuron's axon, at the neuromuscular synapse
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| synaptic vesicles are small | secretory vesicles in the cytoplasm of the synaptic terminal
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| synaptic vesicles contain | acetylcholine
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| neurotransmitter is a | chemical released by a neuron to communicate with another cell
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| acetylcholine is a (ACh) | neurotransmitter that signals the muscle cell to contract; released at the axon terminal
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| synaptic cleft is a narrow space that seperates | the synaptic terminal from the motor end plate of the skeletal muscle fiber
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| acetylcolinesterase or cholinesterase | is an enzyme which breaks down ACh molecules and is released into the synaptic cleft
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| an electrical impulse arrives at the | synaptic terminal
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| ACh is released and | binds to receptor sites on motor end plate
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| a change in local transmembrane potential occurs and results in | generation of an electrical impulse, or action potential
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| electrical impulse travels | all over the surface of the sarcolemma and into each T tubule
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| action potential's continue to be | generated until AChE removes the bound ACh
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| immediately after ACh signals a single contraction it is | broken down by AChE
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| each muscle fiber must be | served by a neuromuscular junction
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| motor unit consits of one | motor neuron and all the skeletal muscle fibers it innervates(controls)
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| motor units contain different | numbers of muscle fibers distributed widely within a muscle
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| the size of a motor unit indicates | the level of control of the movement
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| a motor neuron that controls 2 or 3 muscle fibers (eye) has more | precise control of muscle movement than a motor neuron that innervates up to 2000 muscle fibers (leg)
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| muscle twitches contain different | numbers of muscle fibers distributed widely within a muscle
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| all-or-none principle states that a characteristic in which each muscle fiber | either contracts completely or not at all
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| all or none principle says that all muscle fibers in a motor unit | contract simultaneously
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| all or none principle says that the amount of force, exerted by the muscle as a whole, depends on | how many motor units are activated
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| recruitment is the smooth, but | steady incrase in muscular tension that is produced by increasing the number of motor units that are activated
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| muscle tone is teh | resting tension in a skeletal muscle
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| in a resting muscle, some | motor units are always active w/o producing enough tension to cause movement, but the activity tenses the muscle
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| intermediate fibers contract | quickly
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| fast glycolytic fibers or white fibers are .... fibers bec.... | white...contain little myoglobin
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| few...are in white fibers...but there are | mitochondria or capillaries...abundant glycosomes that contain glycogen as a fuel source
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| white fibers contract...fatigue | rapidly...quickly
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| levers are | rigid bars or structures that move on a fixed point
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| fixed point is called | fulcrum
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| when effort is applied to the lever | a load is moved
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| a motor neuron that controls two or three muscle fibers (eye) has more...control of muscle movement than a motor neuron that.. | precise...innervates up to 2000 muscle fibers (leg)
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| muscle twitch | a single, momentary contraction, which is a response to a single stimuli
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| muscle twitches contain different | numbers of muscle fibers distributed widely within a muscle
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| all or none principle says that a characteristic in each muscle fiber either | contracts completely or not at all
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| all or none princple says that all muscle fibers | in a motor unit contract simultaneously
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| all or none principle says that the amount of force exerted by the muscle as a whole depends on | how many motor units are activated
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| recruitment is the smooth, but | steady, increase in muscular tension that is produced by increasing the number of motor untis that is activated
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| muscle tone | the resting tension in a skeletal muscle
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| muscle tone in a resting muscle, some motor units are | always active without producing enough tension to cause movement, but the activity tenses the muscles
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| muscle tone stabilizes the | position of bones and joints
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| muscle spindles are specialized muscle cells that are monitored by | sensory nerves, which control the muscle tone in the surrounding muscle tissue
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| muscle hypertrophy is the enlargment of | skeletal muscles that undergo excessive repeated stimulation that produces near maximal tension
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| muscle atrophy is reduction in | skeletal muscle size, tone, and power, as a result of inadequate stimulation to maintain resting muscle tone in the affected area
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| types of skeletal muscle fibers | slow oxidative (red I), intermediate (fast oxidative, IIa),fast glycolytic fibers (white, type IIx)
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| red fibers are relatively | thin fibers which are red becasue of their abundant myoglobin
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| red fibers obtain energy from | aerobic metabolic reactions
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| red fibers contract...extremely... | slowly...resistant to fatigue as long as enough oxygen is present
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| red fibers deliver | prolonged contractions
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| red fibers are best for | maintaining postures
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| inter. fibers contract | quickly
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| inter. fibers are...dependent and have a high... | oxygen...myoglobin content and have abundant mitochondria and a rich capillary supply
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| inter. fibers are fatigue | resistant but less so than type I
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| inter. fibers are...in many of their characteristrics compared to types I and IIx | intermediate
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| inter. fibers are best for | long term production of fairly strong contractions such as required locomotion of the lower limbs
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| white fibers are...fibers because... | pale...they contain little myoglobin
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| white fibers are about | twice the diameter or type I fibers
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| white fibers contain more | myofilaments
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| white fibers generate much more | power
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| white fibers depend on | anearobic patheways to make ATP
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| few...are present in white fibers but there are... | mitochondria or capillaries...abundant glycosomes that contain glycogen as a fuel source
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| white fibers contract | rapidly and fatigue quickly
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| white fibers are best for | short burts of power, such as required in lifting heavy objects for brief periods
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| lever is a rigid | bar/structure that moves on a fixed point
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| fixed point | fulcrum
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| when effor is applied to the lever | a load is moved
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| in the human body | bones = levers, joint = fulcrum, effort is exerted by skeletal muscles pulling on their insertions
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| 1st class levers (effort-fulcrum-load) may operate at a | mechanical advantage or disadvantage
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| 2nd class levers (fulcrum-load-effort) all work at a | mechanical advantage
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| 3rd class levers (fulcrum-effort-load) all work at a | mechanical disadvantage
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| most muscles of the body are in | 3rd class lever systems to provide speed of movement
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| mechanicnal advanctage allows | slow and strong movements
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| mechanical disadvantage allows muscles to | move quickly and far but takes extra effort
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| fascicle = | bundle of muscle fibers
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| parallel muscle | long axes of the fascicles are parallel to the long axis of the muscle, and the muscle extends from origin to insertion
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| most of the skeletal muscles in the body are | parallel muscles
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| parallel muscles have a | central body, or belly/gaster
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| example of parallel muscle | biceps brachii
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| convergent muscle | origin is broad, and the fascicles converge toward the tendon of insertion, its common attachment site
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| convergent muscle fibers may pull on a | tendon, or tendinous sheet, or a slender band of collagen fibers known as a raphe
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| example of convergent muscle | pecoralis major of anterior chest
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| circular muscle (sphincter) | fascicles are arranged in concentric rings around an opening or recess
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| in a circular muscle, when the muscle contracts, the diameter | of the opening decreases
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| example of circular muschle | orbicularis oris
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| pennate muscle (penna -feather) the fascicles are | short and attach at an oblique angle to a tendon that runs through the body of the muscle
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| unipennate | fascicles insert into one side of the tendon
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| example of unipennate | extensor digitorum longus muscle
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| bipennate | fascicles insert into both sides of the tendon
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| example of bipennate | rectus femoris muscle of thigh
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| multipennate | fascicles insert into a tendon that branches within the muscle
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| arrangement of multipennate muscles look like many | feathers situated side by side, whose quills are all inserted into one tendon
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| example of multipennate | deltoid muscle of shoulder
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| skeletal muscles are arranged in | opposing groups across movalbe joints, allowing one group of muscles to reverse or modify the action of the opposing group
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| agonist (prime mover) | muscle whose contraction bears the main responsibility for a particular movement
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| example of agonist | biceps brachii for forearm flexion of the elbow
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| antagonist | groups of muscles whose actions oppose that of the corresponding agonist
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| example of antagonist | triceps brachii during forearm flexion but they also act as antagonist by extending the forearm
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| synergists aid the | agonists either by adding a little extra force to the same movement or by reducing undesirable extra movements that the agonist may produce
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| synergists stabilize | joints as fixators
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| naming skeletal muscles | location, shape, relative size, direction of fascicles, location of attachments, number of origins, action
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| brachialis muscle | arm
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| intercostal muscles | between ribs
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| externus or supericialis | describe muscles that are visible at the body surface
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| internus/profundus | describe muscles lying beneath the body surface
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| extrinsic | superficial muscles that position/stabilize organs
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| intrinsic | deep muscles that function within the organ
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| trapezius | trapezoidal shape
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| deltoid | triangular
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| rhomboideus | rhomboid
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| orbicularis | circle
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| magnus/major/maximus vs | minor/minimus
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| longus (long)/longissimus vs | brevis
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| teres | long and round
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| rectus | straight
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| transervsus | fascicles lie at right angles
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| oblique | fascicles lie at oblique angles
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| origin is always | named first
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| biceps, triceps, quadriceps | 2, 3, 4
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| flexor vs | extensor
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| abductor vs | adductor
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| exceptions | platysma and diaphragm
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