Physiology 206 Lecture 10 Outline of Last Lecture I Cholinergic neurons II Somatic branch of nervous system III Neurotoxins Outline of Current Lecture I Muscle II Thick filaments III Thin filaments IV Contraction V Types of contraction Current Lecture 2 7 14 Muscle 3 categories o Skeletal voluntary striated muscle o Smooth involuntary visceral non striated o Cardiac heart muscle Voluntary muscles can be consciously controlled Muscle cells are cylindrical o Muscle fiber muscle cell Myofibrils long cylindrical groups of proteins o Actin thinner known as thin filaments o Myosin thicker known as thick filaments o acto mysolin fibers Muscles generate tensions Thin filaments bundles of actin Thick filaments made up of myosin Thin and thick filaments These 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 o Regular repeting array o Lengthwise along muscle Cross bridges molecular connections between thick and thin filaments near tip o Give muscle cell longitudinal rigidity Muscle cells bound together to form a muscle Sarcomere length 2 micormeters Biological systems use ATP made by mitochondria Motor neuron o release Ach onto the motor endplate o Ach binds cholergenic receptors onto the endplate o Generates action potential in muscle Sarcolemma is smooth covering that dips into cytoplasem t tubules Action potential propagated through entire plasmolemma and down into sarcolemma o Down into body of cell onto sarcoplasmic reticulum Sarcoplasmic reticulum o Releases calcium into cytoplasm o Release of calcium causes contraction Contraction o Sliding Filament Mechanism Myofibrils slide across each other Ends of thin and thick filaments become closer Shortens muscle o Isometric contraction Generate force without shortening Cells shorten but muscles don t o Isotonic contraction Can shorten without generating force Generate motion at constant force Movement of limbs Length tensions Diagrams Tension Length Passive Tension o As you increase length you increase tensions o Not active no energy required o Elasticity stretchability of muscles Tension Active Tension I I I I I electricity Length Tension will increase reach a maximum then decline With the little tension the ends of the thick and thin filaments are far apart At maximum tension the ends of thick and thin filaments are completely aligned
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