A&P.tricOH.ch9.muscles.fall2008
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| muscular system-function (7) | 1. Body movement 2. maintenance of posture 3. respiration 4. production of body heat 5. communication (speaking, gesturing, facial expression) 6. constriction of organs and vessels (internal) 7. heart beat
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| PROPERTIES of muscle | 1. contractility 2. excitability (respond to stimulus 3. extensibility (stretch & come back) 4. elasticity (recoil to original length)
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| contractility | ability of muscles to shorten forcefully - causes movement of structures to which it is attached; or increase pressure inside organs or vessels
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| excitability | capaciy of muscle to respond to stimulus Ex cardiac muscles-can respond to hormones or nerves
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| extensibility | muscle can be stretched beyond its normal limit and contract
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| elasticity | ability of muscle to recoil to its original resting length after it has been stretched
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| types of muscle tissue (3) | skeletal, smooth, cardiac
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| skeletal muscle is how much of the body's weight? | 40%
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| skeletal muscle is responsible for | locomotion, facial expression, posture, respiratory movements and many other body movements -
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| how are skeletal muscles controlled? | the nervous system controls VOLUNTARILY
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| Smooth muscle | hollow organs & tubes
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| what is most widely distributed kind of muscle? | smooth muscle (think long intestine!
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| Cardiac muscle | found only in the heart- AUTORHYTHMIC - contract spontaneosly at regular intervals
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| what are skeletal muscle cells called? | skeletal muscle FIBERS
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| are skeletal muscle fibers short & stumpy? | Each skeletal muscle fiber is a single, long, cylindrical cell containing SEVERAL nuclei
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| Where are the nuclei located in skeletal muscle tissue? | Around the periphery of the fiber near the plasma membrane
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| myo | gr. "muscle"
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| how many new muscle fibers do you get every week???? | number of skeletal muscle fibers remains relatively constant after birth
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| myoblasts | multinucleated cell -immature - primordial muscle cell
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| muscle fiber | skeletal muscle cell
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| what happens shortly after the myoblasts form? | nerves grow into the area and innervate the developing muscle fibers
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| striated | L. "striatus" - furrowed striped appearance
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| sarcolemma | plasma membrane in muscle fiber cell Gr. "lemma" meaning "husk"
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| sarco | Gr. combining form meaning "muscle" or flesh
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| endomysium | a delicate netwrok of loose connective tissue with numerous reticular fibers, surrounds each muscle fiber outside the external lamina
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| peri mysium | a bundle of muscle fibers with their endomysium is sourrounded by another heavier connective tissue layer called the perimysium
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| fasciculus | each bundle ensheathed by perimysium is a muscle fasciculus
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| fascia pl. fasciae | a.) a sheet of fibrous tissue that envelops the body beneath the skin; b. encloses muscles and groups of muscles and separate their several layers or groups
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| epimysium | a dense, collagenous connective tissue and which covers the entire surface of the muscle
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| a muscle consists of many __________ grouped together and surrounded by a (third and heavier) layer of ___________ | muscle consists of many fasciculi grouped together and surrounded by a (third and heavier) layer of epimysium
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| fascia around an individual muscle is also called | epimysium
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| motor neuron | special nerve cells; cell bodies in brain or spinal cord - axons extend to skeletal muscle fibers through nerves
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| what do motor neurons do? | stimulate muscles to contract
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| hypertrophy | # of muscle fibers remains constant throughout life - genetics & exercise can increase the size, but not the number of muscle fibers
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| axons | motor neurons - the "tail" of the nerve cell, extending the length of the muscle fiber - branch at level of the perimysium throughout muscle fiber
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| arteries and veins in muscle fibers | an arter7 and 1 or 2 veins extend together with a nerve through the connective tissue layers of skeletal muscle remember ARTERY-VEIN-NERVE the three stooges!! of muscle action
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| sarcoplasm | the name given to cytoplasm within myofibrils
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| myofibril | a threadlike structure approximately 1-3 "U" m in diameter that extends from one end of the muscle fiber to the other
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| myofilaments | there are two main kinds of protein filements in muscle: actin "thin" myofilaments and myosin "thick" microfilaments
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| actin myofilaments | composed of tropomyosin - and troponin
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| tropism | the phenomenon, ovserved in living organisms, of moving toward or away from light, heat or other stimulus
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| tropomyosin | a fibrous protein extractable from muscle - runs; each is long enough to cover seven G actin sites
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| troponin | proteins that function as regulators of muscle contractions
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| how many different proteins does troponin have? | three - one binds to actin, one binds to tropomyosin, and the third binds to calcium ions
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| Z disk to Z disk | sarcomere extends from one Z line to another
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| cross bridge | heads of myosin myofilaments (thick) can bind to active sites on the actin molecules to form cross-bridges
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| ATPase | enzymes that break down ATP - releasing energy
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| sliding-filament mechanism | includes all events that result in actin myofilaments fliding over myosin myofilaments to shorten the sarcomeres of muscle fibers.
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| do actin and myosin fibers change length during muscle contractions? | NO - actin & myosin myofilments slide past one another
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| what is shortened during a muscle contraction? | the SARCOMERE is shortened
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| what zone disappears during a muscle contraction? | the H zone
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| six steps of the sliding-filament mechanism | 1. CA2+ binds troponin - shape is altered 2. tropomyosin can slide away from the actin active site (it "opens") 3. myosin heads interact with actin and "walk" toward center of sarcomere 4. detachment of actin & myosin 5. cross-bridge- myosin head binds t
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| what is contraction the result of? | contraction is the result of ACTION POTENTIALS
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| action potentials are | electric signals - which travel from the brain or spinal cord along the axons to muscle fibers and cause them to contract
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| resting membrane potential | 1. plasma membranes are POLORIZED (there is a voltage difference across each plasma membrane 2. the charge difference across the plasma membrane of an unstimulated cell is called the resting membrance potential
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| relative concentration of Na+ and K+ | the Na+-K+ pump moves Na+ to the outside of the cell and K+ to the inside of the cell; but the positively charge K+ cells tend to diffuse out of the cell through k+ channels leaving the netatively charged molecules behind, thus polaring the membrane
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| are channels for K+ gated? are they open? | K+ are NON-gated & they are open continuously- the resting membrane potential is established
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| ligand-gated channels | "LIGANDS" bind to receptors, which are proteins with receptor sites
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| when do ligand-gated channels open? | they open in response to a ligand bind to a receptor that is part of the ion channel
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| ion | atom or group of atoms carrying an electric charge having gained or lost one or more electrons (cations - positive; anions-negative)
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| neurotransmitters release | ligands - which bind to ligand-gated Na+ channels in the membranse of the muscle fibers
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| voltage-gated ion channels | open & close in response to small voltage (charge) across the the plasma membrane
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| are voltage-gated ion channels open to all? | NO - they are "members only" Na+ and K+ each have their own channels
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| Action potential | the change in membrane potential occurring in muscle tissue when excitation occurs
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| Depolarization | inside of plasma membrane becomes less negative
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| threshold is reached when | depolarization phase changes the membrane potential to a certain value
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| what happens when threshol is reached? | action potential is triggered
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| what is repolarization? | membrane is returned to resting value (re-polarization equals re-sting)
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| All or none principle | like a flash system of a camera, if the shutter is depressed, the flash goes - when the cell has a stimulus to depolarize, the voltage-gated channels will open & bring NA+ in, which depolarized the cell, then K+ voltage channels will open, which will caus
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| Do action potentials move in one action across the cell membranes? | NO - they are like dominoes - one cell stimulates an adjacent location, which must then go through the resting potential-depolarization-action potential - repolarization resting potential cycle by itself; action potentials move like dominoes
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| Action potential frequency is affected by | the strength of the stimulus
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| synapse | syn Gr. "joined" or "together" and Gr. Hapto "to clasp"
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| presynaptic terminal | the axon terminal - part of the neuromuscular junction
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| neuromuscular junction consists of | axon terminals and the area of the muscle fiber sarcolemma they innervate
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| an axon terminal is a | presynaptic terminal
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| the space between the axon terminal and the muscle fiber is | the synaptic cleft
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| the muscle plasma in the are of the junction is the | postsynaptic membrane or motor end-plate
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| muscle contraction - afternerve initiated stimulus | 1. action potential reaches presynatpic terminal 2. voltage-gated Ca2+ channels in axonplasma membrane open 3. Ca2+ enters axon - 3. acetylcholine exocytosed from vesicle 4. acetylcholine binds to ligand-gated Na+ channels in sarcolemma 5 releases Na+, wh
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| how does cell ensure that only one action POST-synapse action potential for everyone on PRE-synaptic action potential? | acetylcholinesterase
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| excitation-contraction coupling | action potentials can lead to contraction of the fiber-the entire mechanism involving the sarcolemma, t-tubles, sarcoplasmic reticulm, Ca+ and troponin
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| sarcoplasmic reticulum | sarco "muscle" (meaning a formation in the muscle) reticulum L. combining form meaning "net"
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| plasma | combining form meaning "something formed"
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| sarcoplasmic reticulum & T tubules | when action potentials are propagated, they surge through the sarcoplasmic reticulum & T tubules into the sarcomeres in myofibril; Ca2+ then binds to troponin - which then opens tropomyosin & troponin - a cross-bridge can be formed -
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| what happens after Ca2+ is released from sacroplasmic reticulum? | the cross-bridge is formed as Ca2+ binds to troponin which "turns toward" an opening & the tropomyssin opens
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| cross bridge movement - action | ATP - myosin is at rest - ADP & phosphate are bound to myosin head, one ATP must be utilized for myosin to release actin
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| power stroke | movement of the myosin molecule while the cross-bridge is attached is called the POWER STROKE
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| recovery stroke | return of the myosin head to its original position after cross-bridge release is called the recovery stroke
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| muscle twitch | contraction of a muscle ins response to a stimulus in one or more muscle fibers
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| lag or latent phase of muscle twitch | the time between application of the stimulus to the motor neuron & the beginning of the contraction
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| contraction (muscle twitch) | time during which contraction occurs
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| relaxation (muscle twitch) | muscle has contracted & rest; muscle fibers lengthen passively
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| does whole muscle contraction occur like muscle twitch??? | no, it can occur in graded fashion (muscle twitch is all-or-none)
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| what two ways can you vary the amount of tension in a whole muscle? | 1. FREQUENCY of stimulation or 2. NUMBER OF MOTOR UNITs stimulated
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| rigor mortis is caused by what after death? | lack of ATP - no cellular metabolism
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| tetanus complete & incomplete | in complete tetanus, action potentials are produced so rapidly that NO RELAXATION occurs
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| motor units | consists of a single motor neuron and all the muscle fibers it ennervates
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| graded muscle contraction | in WHOLE Muscle contraction, the stimuli can be weak or strong,
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| multiple motor unit summation | as more & more motor units are stimulated, the force of the contraction is greaterd
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| subthreshold stimulus | not strong enough; no action potentials and therefore no movement
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| threshold stimulus | strong enough to produce an action potential in a single motor unit axon
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| stimulus frequency | is there rest before the next action potential?
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| does rapid, repeated stimulation of a muscle fiber increase its force of contraction? | yes, this increased tension is called multiple-wave summation
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| multiple-wave summation | as the frequency of action potentials increase, the frequency of contraction increases
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| incomplete tetanus | muscle fibers partially relzx between contractions
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| complete tetanus | action potentials are produced so rapidly in muscle fibers that no muscle relaxation occurs between them
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| tetanos | L from Gr - convulsive tension
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| treppe | staircase
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| treppe muscles | when a rested muscle is stimulated at a frequency that allows complete relaxation between stimuli, the second contraction produces slightly greater tension than the first, and the third contraction produces greater tension than the second - "warmup on the
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| muscle contractions - isometric | "iso" means "equal" - muscle length is same; remains constant - Posture is maintain in isometric concentration - postural muscles that hold the spine erect
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| isotonic | "equal" tonic refers to muscle tension; TENSION is constant while length of muscle changes -movements of arms or fingers
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| concentric muscle | a muscle produces increasing tension as it shortens - most muscles of body
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| eccentric contractions | isotonic contractions in which a muscle produces tension, but the length of the muscle is increasing
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| muscle tone | the constant tension produced by muscles of the body for long periods of time-responsible for keep back straight & head upright
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| active tension | force applied to an object to be lifted when a muscle contracts - the initial length of a muscle has a strong influence on the amount of active tension it produces - ex. weightlifters crouch so muscles are stretched close to their optimum length before li
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| active tension curve | if muscle is NOT stretched, little tension is produced - also, if overstretched because actin & myosin myofilaments are not being utilized for movement - when muscle is optimally stretched, the number of crossbridges formed is maximal
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| fatigue | decreased capacity to do work - reduced efficiency of performance
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| psychologic fatigue | person believes that additional muscular work is possible
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| muscular fatigue | results from ATP depletion - most common type
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| synaptic fatigue | in neuromuscular junction; under extreme exertion - insufficient acetylcholine is released to stimulate muscle fibers
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| muscle soreness & exercise | develops 1-2 days after training - inflammation to muscle fibers & connective tissue
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| types of muscle soreness | shin splints (inflammation in anterior tibial compartment) plantar fascitis ("falling arches) patellofemoral (runner's knee)
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| rigor mortis | rigid muscles after death 1.) ATP production stops shortly after death 2. CA+2 leaks into sarcoplasma 3. cross-bridges form as Ca+2 4. However, little ATP is available to bind the myosin molecules, so the cross-bridges are unable to release and re-from in
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| energy sources | ATP provides immediate source of energy; it must be synthesized continuously
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| where does energy to produce ATP come from (only a small amount can be stored) | 1. creatine phosphate 2. anaerobic respiration and 3. aerobic respiration
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| creatine phosphate | during resting conditions, energy from aerobic respiration is used to synthesize creatine phosphate
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| anaerobic respiration | occurs in absence of oxygen and results in the breakdown of glucose to yield ATP and lactic acid-used during bursts of energy
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| aerobic respiration | requires oxygen and breaks down glucose to produce ATP, carbon dioxide and water.
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| oxygen debt | after intense exercise, AEROBIC metabolism keeps going to restore ATP levels
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| slow-twitch-high-oxidative or TYPE I muscle fibers | contract more slowly, are smaller in diameter; have more blood supply, more miochondria, and are more fatigue-resistant
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| what are slow-twitch muscle fibers sometimes called? | high-oxidative muscle fibers - Ex. dark meat in chicken legs & thighs
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| myoglobin | darkpigment similar to hemoglobin; binds oxygen & acts as a reservoir when blood does not supply adequate amount
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| fast-twitch, low-oxidative or TYPE II muscle fibers | respond to nervous stimulation; contain myosin molecules that break down ATP more rapidly; cross-bridges from , release & re-form rapidaly- very little myoglobin (white color) and fewer mitochondria Ex. in chickens, white meat is on breast of wings--they
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| source of long-term energy | aerobic respiration-complete glucose breakdown to produce 36 or 38 ATP
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| slow twitch muscles | long distance runners, cycling, swimming
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| duchenne's muscular dystrophy | muscular weakness-waddling gaitwasting of the skeleton
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| what makes muscles extensible and elastic? | titin-on myosin filaments - like a watch spring nebulin- hold thin filaments on the Z line
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| Blocking acetylcholine receptors and acetylcholinersterase | 1. insecticides bind & inhibit functions of acetylcholinesterase - therefore, muscle are constantly stimulated- SPASTIC PARALYSIS - if humans get insecticide in system, they will die of respiratory paralysis
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| curare - flaccid paralysis | curare binds to acetylchline receptors, preventing acetylcholine from binding; therefore, the muscle cannot contract in response to nervous stimulation FLACCID PARALYSIS
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| Myasthenia gravis | antibodies bind to acetylcholine receptors, causing destruction of the receptor, reducing the number of receptors-muscle are weak or exhibit flaccid paralysis
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| muscular atrophy - disuse | decrease in size of muscles due to disuse - bedridden people; limbs in casts
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| denervation atrophy | if nerves are damaged, they will atrophy & FLACCID PARALYSIS is the result - therefore, electrical stimulation to wounds or muscles within casts is necessary to prevent permanent damage
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| muscular dystrophy - on of MYOPATHIES | skeletal muscle is destroyed Duchenne's -sex-linked recessive disorder affecting males - muscles atrophy & are replaced by connective tissue - Faciosapulohumoral muscular dystrophy is an autosomal-dominant condition
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| fibrosis | scarring - replacement of damaged c ardiac muscle or skeltal muscle by connective tissue
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| fibromyalgia | chronic muscle pain syndrome - pain in muscle joints muscles & tendons (not in joints)
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| origin or head of muscle | most stationery part
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| insertion | end that is attached to bone; greatest amount of movement
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| belly of muscle | middle part (men's arms swell in the belly of well-developed muscle)
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| agonist | muscle accomplishing certain movement Ex. biceps brachii is the agonist in elbow flexion, whereas the triceps brachii is the antogonist (extends the elbow)
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| antagonist | a muscle acting in opposition to the agonist
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| synergists | muscles working together to accomplish desired movement Ex. biceps brachii & brachialis are synergists in elbow flexion
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| fixators | muscles that hold one bone in place relative to body while a more distal bone is moved Ex. muscles of scapula hold it in place while other muscles move the humerus
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| Nomenclature - how are muscles named? | by location, size, shape, orientation, origina & insertion, number of head, or function
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| location - muscle named by | pectoralis, gluteus, brachial
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| muscle named by size | maximus, longus, brevus
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| muscle named by shape | deltoid, quadratus, teres
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| orientation | rectus
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| origin & insertion | sternocledomastoid, brachioradialis
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| number of heads | biceps, triceps
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| function | abductor, adductor, masseter
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