Muscle Action, Recruitment, and Energy Sources. Muscle Activation ► Caused by message from brain...
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Transcript of Muscle Action, Recruitment, and Energy Sources. Muscle Activation ► Caused by message from brain...
![Page 1: Muscle Action, Recruitment, and Energy Sources. Muscle Activation ► Caused by message from brain ► Message sent along motor neuron (nerve cell attached.](https://reader036.fdocuments.in/reader036/viewer/2022062314/56649e5c5503460f94b544b9/html5/thumbnails/1.jpg)
Muscle Action, Muscle Action, Recruitment, and Recruitment, and Energy SourcesEnergy Sources
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Muscle ActivationMuscle Activation
► Caused by message Caused by message from brainfrom brain
►Message sent along Message sent along motor neuron motor neuron (nerve cell attached (nerve cell attached to muscle)to muscle)
►M.n. ends in M.n. ends in synaptic cleftsynaptic cleft
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Synapse Synapse ► Synaptic cleft Synaptic cleft
terminates in terminates in sarcolemma (outside of sarcolemma (outside of muscle cell)muscle cell)
► Releases acetylcholine, Releases acetylcholine, which causes which causes sarcolemma to release sarcolemma to release CaCa++ ions into muscle cell ions into muscle cell
► Begins muscle Begins muscle contractioncontraction
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Action PotentialAction Potential
► Influx of CaInflux of Ca++ ions ions causes an electrical causes an electrical current called action current called action potentialpotential
►Once sarcolemma is Once sarcolemma is activated, begins activated, begins chain reaction along chain reaction along entire muscle cellentire muscle cell
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RememberRemember
►Each muscle is composed of hundreds of Each muscle is composed of hundreds of muscle cells stacked into a bundlemuscle cells stacked into a bundle
►So far we have only activated ONE So far we have only activated ONE muscle fibermuscle fiber
►When a single muscle fiber is activated, When a single muscle fiber is activated, it is an “all-or-nothing” responseit is an “all-or-nothing” response
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Muscle recruitmentMuscle recruitment
► If more force is If more force is needed, nerve will needed, nerve will activate more activate more muscle fibers in the muscle fibers in the fascicle (muscle fascicle (muscle recruitment)recruitment)
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Another way to provide more Another way to provide more forceforce
►Nerve can also Nerve can also increase rate of increase rate of stimulation, stimulation, causing muscle to causing muscle to contract fastercontract faster
► Can reach complete Can reach complete tetanus (full tetanus (full contraction with no contraction with no relaxation)relaxation)
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Other forms of contractionOther forms of contraction
► Twitch- short, weak Twitch- short, weak signal causes brief signal causes brief contractioncontraction
► Summation- Summation- contraction rate contraction rate increases (no complete increases (no complete relaxation)relaxation)
► Incomplete tetanus – Incomplete tetanus – faster rate; faster rate; contractions closer contractions closer togethertogether
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Complete TetanusComplete Tetanus
► Continuous contraction Continuous contraction with no relaxationwith no relaxation
► Evident in isometric Evident in isometric exerciseexercise
► Also happens as a Also happens as a result of some diseases result of some diseases and infectionsand infections RabiesRabies C. tetaniC. tetani
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In reviewIn review
►Two ways to increase forceTwo ways to increase force Recruit more musclesRecruit more muscles Increase rate of contractionIncrease rate of contraction
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Energy for ContractionEnergy for Contraction
► 3 possibilities3 possibilities
1) Aerobic respiration1) Aerobic respiration
2)Lactic acid 2)Lactic acid fermentationfermentation
3)Direct 3)Direct phosphorylation phosphorylation (fastest, but only lasts (fastest, but only lasts about 20 seconds)about 20 seconds)
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Direct PhosphorylationDirect Phosphorylation
► ADP encounters ADP encounters Creatine Phosphate Creatine Phosphate (CP)(CP)
► Takes phosphate Takes phosphate molecule to form molecule to form ATP, leaves ATP, leaves creatinecreatine
► CP only present in CP only present in muscle cellsmuscle cells