BIOL 460 1st Edition Lecture 18Outline of Last Lecture I. Muscle Twitch II. Skeletal Muscle Fiber TypesIII. Cardiac Muscle IV. Smooth MuscleOutline of Current Lecture I. Smooth Musclea. Multiunit b. Single unitc. Excitation/contraction coupling II. The Heart/Circulatory System (Chapter 9)Current LectureSmooth Muscle Review 1. Innervated by autonomic neurons2. Two typesa. Multiunit – iris of eye; individual smooth muscle cells all receiving innervation by one axonb. Single Uniti. Much more commonii. Walls of hollow organsiii. Innervation by synapses en passantiv. Cells are connected together with gap junctionsv. All contract togethervi. Generate peristaltic waves3. Non-striated – no A and I bands, no sarcomeres4. Cells are spindle shaped, uninucleate5. No z discs, thin filaments attach to sarcolemma or masses of protein called dense bodies6. Thick myofilaments are less common (much more actin than myosin, 16:1 ratio)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.7. Thick myofilaments are composed of myosin organized with cross bridges parallel to shaft (unlike skeletal muscle)8. No bare zone without cross bridges9. LOOK AT FIGURE 12.3710. Single unit SM – innervation occurs via gap junctions11. Smooth musclea. More thin:thick ratio (16:1) than skeletal muscle (2:1)b. No bare zone on thick myofilamentc. Cross bridges parallel to myosin bandd. Makes smooth muscle better able to stretche. Slow, sustained contractions (slow myosin ATPase’s)12. Excitation/Contraction coupling in Smooth musclea. Trigger is Ca2+ from extracellular environment (NOT FROM SR)b. Sarcolemma contains Ca2+ VGCc. EPSPs/Graded contractions – result of amount of Ca2+ going in celld. Low Ca2+, weak contractione. High Ca2+, strong contractionf. No troponin or tropomyosing. Ca2+ in cell, bonds to calmodulin, making Ca2+/calmodulin complexh. Activates myosin light chain kinasei. Phosphorylates myosin light chainsj. Cross bridges attach to thin myofilaments and cross bridge cyclek. Turning contraction ofi. Ca2+ pumped out of sarcopasm via Ca2+ pumpsii. Myosin phosphatase dephosphorylates myosin light chains The Heart/Circulatory System (Chapter 13)1. Right atrium2. Right ventricle3. Left atrium4. Left ventricle5. Atria separated by interatrial septum6. Ventricles separated by interventricular septum7. Fibrous skeleton – band of connective tissue in walls of ventricles and valves8. Valves prevent backflowa. AV valvesi. R – tricuspidii. L – bicuspidiii. Flaps are connective tissueiv. Underside connected to connective tissue fibers (chordae tenineae) otherend connects to papillary muscles in ventriclev. This holds the valve in place so they don’t open the other way during contractionvi. Murmurs1. Backflow due to damaged valve2. Caused by streptococcus pyrogenase (antibodies for strep attach to connective tissues in body, causing destruction of those cells)3. Don’t class all the way –
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