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Notes: Sliding Filament Theory

Notes: Sliding Filament Theory. [Muscle Contraction Physiology]. (1) Muscle Contraction. Sliding Filaments = Muscle Contraction The Basic Steps: 1- Message sent 2- Neurotransmitter 3- Depolarization 4- Calcium + Troponin = Actin Exposed 5- Actin + Myosin (Contraction).

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Notes: Sliding Filament Theory

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  1. Notes: Sliding Filament Theory [Muscle Contraction Physiology]

  2. (1) Muscle Contraction • Sliding Filaments = Muscle Contraction • The Basic Steps: 1- Message sent 2- Neurotransmitter 3- Depolarization 4- Calcium + Troponin = Actin Exposed 5- Actin + Myosin (Contraction)

  3. (2) Neuron  Muscle (Muscle Fiber) • Cause: • Conscious decision to move • Homeostatic response • Nervous System  Effector • Neurotransmitter released (ACh, acetylcholine) • ACh binds to sarcolemma of muscle fiber • ACh initiates opening of sodium-potassium channels

  4. (3) Depolarization • Cause: • Binding of ACh to sodium-potassium channels • Opening of channels + Movement of Na-K+ across sarcolemma • Movement of Charges: • More Na+ moves in, Than K+ moves out • Imbalance of charges  electrical current (action potential)

  5. (4) Sarcoplasmic Reticulum  Calcium • Cause: Depolarization • Action Potential releases Calcium: • Ca+ released from membrane of sarcoplasmic reticulum to sarcomere • Ca+ binds with troponin: • Troponin-Tropomyosion conformation changes • Troponin & Tropomyosin no longer cover Actin • Actin is exposed

  6. (5) Myosin  Actin • Cause: • Troponin & Tropomyosin unveils Actin • Actin exposed • Myosin releases Inorganic Phosphate + ADP • Pi + ADP = ATP • Myosin changes conformation • Myosin binds to Actin • Myosin and Actin slide towards each other • WE HAVE A CONTRACTION! WOO WOO!

  7. (6) Relaxation • ATP binds back with myosin… • Myosin detaches and moves away from Actin • Troponin & Tropomyosin cover up Actin • Ca+ moves back into Sarcoplasmic Reticulum • Repolarization  Sarcolemma stable again

  8. (7) Why is it called the Sliding Filament Theory? • Movement of myofilaments causes contraction • Myosin grabs actin & SLIDES them towards the center

  9. (1-2) Depolarization of Sarcolemma & Generation of Action Potential (3) Calcium Ions released from Sarcoplasmic Reticulum (10) Everything moves back & contraction done! (4-6) Calcium binds to troponin, tropomyosin moves, actin exposed (9) Calcium removed by active transport (7-8) Myosin attaches to actin, Myosin moves actin, ATP released

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