UWL BIO 312 - Final Exam Study Guide (10 pages)

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Final Exam Study Guide

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Final Exam Study Guide


Summary of lectures 19-23.

Study Guide
University of Wisconsin-La Crosse
Bio 312 - Human Anatomy and Physiology I
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BIO 312 1st Edition Final Exam Study Guide Lecture 19 Introduction to Muscles Muscle Characteristics One of the 4 primary tissues 3 types Skeletal smooth cardiac Specialized to generate force produce movement perform work Converts chemical energy ATP into mechanical energy and heat Comprises about 40 50 of body weight most skeletal Characteristics o Excitability ability to change membrane potential o Contractility ability to contract and move bones o Extensibility ability to stretch and withstand force o Elasticity ability to recoil back to original length when stretched Striated muscle has striped appearance under microscope o Skeletal and cardiac muscle Unstriated muscle has smooth non striped appearance under scope o Smooth muscle Voluntary skeletal muscle Involuntary smooth and cardiac muscle Anatomy and Histology Each muscle consists of o muscle cells fibers o Endomysium connective tissue that covers each muscle fiber o Fascicle bundle of parallel muscle fibers covered by perimysium Length of cells muscle length o Epimysium connective tissue that covers several fascicles that make up the muscle as a whole o Blood and lymphatic vessels o Efferent and afferent nerves Skeletal Muscle Fiber structure much larger cells than smooth or skeletal o Sarcolema muscle cell membrane contains many sodium gated and voltage gated ion channels o Sarcoplasm cytoplasm of muscle cell o Mitochondria very high density of mitochondria for ATP production o Contain several nuclei on periphery of cell under sarcolema o Myofibril tube like structures that compose majority of volume of muscle cells Number of myofibril per cell vary based on diameter of cell Arranged parallel to the long axis of the muscle Structures that shorten and do the work during contraction Each myofibril loosely surrounded by series of membranes and sacs called sarcoplasmic reticulum o Striations repeating pattern of bands along each myofibril Sarcomeres one repeating unit of striations that is the basic unit of contraction in striated muscle Z line to z line A band dark bands of striated muscle composed primarily of thick filaments Length does not change during contraction I band lighter bands of striated muscle Gets shorter during contraction Z line divides I band in half anchors thin filaments and titin filaments o Myofilaments 3 different types of protein fibers that make up sarcomeres Sliding filament mechanism Huxley 1954 contraction results from sets of tin and thick filaments sliding past each other To shorten thin slide past thick filaments towards center of sarcomeres o Length of myofilaments does not change o Thick filament thicker filaments composed of myosin make up A band H zone central portion of A band where thick and thin filaments do not overlap Essentially disappears during contraction M line anchor point for center of A band Composed of several hundred myosin molecules shaped like golf clubs Shafts of bundles of myosin called tails make up bare zone Ends of golf clubs called heads that make up cross bridges and attach to thin filaments responsible for contraction by pulling thin filaments inward Contain ATPase binding site and Actin binding site o Titin filaments anchor thick filaments in place Not directly involved in contraction Elastic structural protein o Thin filaments thinner filaments made from actin anchored to Z lines G Actin molecules contain binding site for attachment with myosin F Actin molecules G actin composed double stranded helical strand of protein Tropomyosin thin filamentous protein that coat the outer surface of actin backbone Troponin three different proteins associated with tropomyosin o Cross Bridge Cycle Binding myosin cross bridge to actin molecule Power Stroke cross bridge bends pulling thin myofilament inward Detachment cross bridge detaches at end of power stroke and returns to original shape Binding cross bridge binds to more distal actin molecule cycle repeated Cycles operate asynchronously to provide smooth coordinated movement Chemical events of cross bridge cycle o Myosin cross bridge attaches to actin filament o ATP ADP P during power stroke waste products sloughed off o ADP P ATP allows for usable energy to relax cross bridge entire muscle Thick and thin filaments are called contractile protein because their interaction produces tension and shortening of sarcomere High degree of three dimensional order allows maximum amount of myosin myosin and actin actin interaction Lecture 20 Muscular contraction and mechanics Muscular Contraction Neuromuscular junction where nerve cell axon synapses with skeletal muscle o Always excitatory somatic muscles are always nicotinic o Synapse in middle of muscle fiber for most uniform action potential throughout fiber Sarcoplasmic reticulum membranous sac surrounding every myofibril stores Ca2 when not stimulated o Releases calcium during stimulation o Active re uptake of calcium when relaxed Transverse tubules invaginations of sarcolemma that occur at regular intervals throughout sarcolemma o Rapidly conduct action potentials to interior of cell so all myofibrils can be activated simultaneously o Action potential passing down T tubule opens nearby calcium channels located on the sarcoplasmic reticulum flooding the area surrounding the myofibrils sarcoplasm with calcium ions o Extensiveness of the sarcoplasmic reticulum assures that when calcium is released it quickly reaches all areas of the myofibrils Role of Ca 2 ions in sarcoplasm o No calcium present means that tropomyosin blocks actin binding sites keeping cross bridges from binding to actin molecules o Raise in concentration of calcium ions rotates actin and revealing the binding sites allowing cross bridges to bind to actin and initiate contraction o Re uptake of calcium into S R causes tropomyosin to go back to blocking actin binding sites causing relaxation of the muscle Action potential initiates Excitation Contraction Coupling 1 Action potential generated and propagated along the sarcolemma and down the T tubule via voltage gated ion channels same as unmyelinated axon 2 Action potential triggers Ca 2 release from sarcoplasmic reticulum 3 Calcium ions bind to troponin removing the blocking action of tropomyosin exposing actin binding sites 4 Myosin cross bridges alternately attach to actin and detach pulling the actin filaments toward the center of the sarcomere release of energy by ATP hydrolysis powers the cycling process 5 Removal of Ca 2 by active transport into SR after the

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