BIO 240 1st Edition Lecture 19Outline of Last Lecture III. Muscle PhysiologyA. Nervous System + Muscle System = ContractionB. Active Channels C. Steps of excitation contraction coupling. Outline of Current LectureIII. Muscle PhysiologyA. Nervous System + Muscle System = ContractionB. Active Channels C. Steps of excitation contraction coupling. D. Sliding Filament Theory E. Steps of Sliding Filament Theory Current LectureIII. Muscle PhysiologyA. Nervous System + Muscle System = ContractionB. Active Channels C. Steps of excitation contraction coupling. D. Sliding Filament Theory When actin and myosin side past one another (machinery of contraction).i. Actin Thin filaments1. Toponin A complex of three large proteins attached to tropomyosin on actin molecules. 2. Tropomyosin A rod shaped protein that spirals around actin and blocks myosin binding sites. 3. Myosin binding sites are located on actin molecules directly behind the tropomyosin. ii. Myosin Thick filaments 1. Myosin heads Form cross bridges with actin by binding ATPThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iii. Crossbridge Formed by the globular heads of myosin when they attachto actin. iv. Power stroke The myosin heads going from a cocked position to a low energy configuration. v. Ratcheting Many power strokes. Process of myosin heads attaching, detaching, and reattaching further back on the actin molecule E. Steps of sliding filament theory i. The calcium molecules that were released from the terminal cisternae bind to troponin. ii. This binding changes the shape of troponin.iii. This change in shape of the troponin pulls tropomyosin off of the myosin binding sites on actin.iv. ATP then activates myosin heads (that were previously in the cocked position), which causes crossbridge formation. v. Myosin pulls actin filament until it is stuck – power stroke.vi. ATP is used for detachement of the myosin heads after the power stroke so that myosin heads return to the cocked position and pull again. 1. Causes shortening of the sarcomeres as myosin is attached to the M-line and actin is attached to the Z-line.2. H-zone and I-band disappear when muscle is contracted. F. Clinical Applicationi. Troponin isoforms are a protein with the same structure as troponin. A simple blood test can be done to see the levels of these proteins. High levels can indicate probability of myocardial
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