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Lecture 16

Lec16 - Skeletal Muscles.doc

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University of Toronto Scarborough
Biological Sciences
Mary Olaveson

Skeletal Muscles1 TopicsNeuromuscular JunctionSkeletal Muscle StructureSarcomere StructureThin actin and Thick myosin Filaments CrossbridgesForce Generation in MuscleRegulation of Actin and Myosin BindingThe Muscle TwitchIsometric and Isotonic ContractionsEffects of High Frequency Stimulation TetanusTypes of Skeletal MusclesRegulating the Strength of Muscle ContractionThe Motor UnitVertebrates vs Invertebrates2 The Neuromuscular JunctionSituation between a nerve and a muscleoThe never is known as a motor nerve exerting motor control over the muscleoThe synapse in general is known as the neuromuscular junctionoAction potential comes down the axonoCauses a neurotransmitter to be released into the synaptic cleftoAcetylcholine is a neurotransmitter that binds to acetylcholine nicotinic receptors on the muscle cellStimulated by nicotineAll muscles in our body are stimulated by nicotineoThe binding causes an action potential which triggers muscles to contract3 Skeletal Muscle StructureThe basic units of the muscle are the muscle cell fibreoThese are very long and run the entire length of the muscleoThey are multinucleated developed from multiple cells fusing togetheroMacroscopic viewThey are bound into these structures called fascicle which are groupings of fibres connected by connective tissue which are bound by more connective tissue which form the muscle as a wholeoMicroscopic viewActin and myosin protein filaments are grouped into myofibrils which collectively make up a single muscle fibre Muscle contracts because the thin and thick respectively protein filaments slide across one another4 Skeletal Muscle StructureMuscle fibres are multinucleated made up of thin actin filaments and thick myosin filaments collectively known as myofibrilsoThe repeating pattern of actin and myosin filaments are known as a sarcomere one contractile unitMitochondria surround the space between myofibrils containing actin and myosin filamentsoRole of hydrolysing ATP in muscle contraction oRole of ATP in muscle relaxationSarcolemma is the plasma membrane of a muscle cellSarcoplasmic reticulum is among other things a site of calcium storageTTubule
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