Lecture 5 - Motor Mechanism

Break types of muscle bers oxida4ve bers contain

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Unformatted text preview: nts –  Each head binds to ac4n and ATP/ADP –  Change in conforma4on depending if it’s ajached to ATP or ADP Doesn’t bind to ac4n Binds to ac4n 32 Muscle  ­ Sliding mechanism •  Myosin state will determine its binding affinity to ac4n filaments •  Cross ­bridge cycle: Addi4on of Ca2+ causes the myosin binding site to be exposed. 33 Muscle  ­ Sliding mechanism •  Cross ­bridge cycle: 34 Muscle  ­ Sliding mechanism •  Cross ­bridge cycle: 35 Muscle  ­ Sliding mechanism •  Cross ­bridge cycle: 36 Muscle  ­ Sliding mechanism •  Cross ­bridge cycle: Removal of Ca2+ causes the myosin binding site to be occluded. 37 Skeletal Muscle – Neurotransmijer junc4on •  Junc4on of motor neuron’s axon and muscle fiber •  Axon divides into terminals containing vesicles of acetylcholine (ACh) •  ACh receptor is a ligand ­gated ion channel •  Na+ flows into muscle cell leading to depolariza4on and an ac4on poten4al 38 Skeletal Muscle Structure •  In muscle cells –  ER = sarcoplasmic re4culum –  Cytoplasm = sarcoplasm •  Sarcoplasmic re4culum is surrounding the myofibril 39 Ac4va4on of Skeletal Muscle •  Ac4on poten4al spreads through T ­tubules, which connect with sarcoplasmic re4culum •  Ac4on poten4al ac4vates Ca2+ ­selec4ve channels in the T ­tubules allowing Ca2+ to move from the sarcoplasmic re4culum to the sarcoplasm – muscle contrac4on •  Ca2+ is taken up by the sarcoplasmic re4culum, termina4ng muscle contrac4on 40 Types of Muscle fibers •  Different muscle fibers contain forms of myosin that differ in the maximal rates at which they can hydrolyze ATP –  Fast fibers contain myosin with high ATPase ac4vity –  Slow fibers have myosin with a lower ATPase ac4vity Doesn...
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This document was uploaded on 03/05/2014.

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