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Unit 3 Muscle.docx

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University of Waterloo
BIOL 273
Catherine Studholme

Unit 3 Muscle A INTRODUCTION TO MUSCLE IntroductionWhat is a Muscleo Tissue specialized to convert biochemical reactions into mechanical work Muscle Function uses contraction to generate motion and generate force o Can only contract o Cannot expand except when physically pulled by antagonistic muscle groupso Also generate heatcontribute to body temperature homeostasis Muscle Types FIGURE 121 o Skeletalattached to bones of the skeleton to generate force for body movementContract in response to signal from somatic motor neuron cannot initiate contraction on its own or influenced by hormones in the somatic nervous system No cellcell binding long cells run the length of a muscleStriations o Smoothprimary muscle of internal organstubes eg stomach blood vessels urinary bladder Small and do not attach to each otherInfluences movement of materials through the body autonomic nervous system No striationso Cardiacfound only in the heart and creates a pump to move blood around the body autonomic nervous system Striations Branched and joined by intercalated disk junctionsB SKELETAL MUSCLEGross Structure of Skeletal MuscleCharacteristicsResponsible for positioning and movement of skeleton skeletal muscles are 40 of body weight Attached to bones via tendons composed of dense regular connective tissue collagen made of protein arranged into cable like fibers Skeletal muscles generally have two attachment pointso Origintends to be the least moveable part of the bodyo Insertiontends to be the most moveable pointTwo types of Muscleso Flexor Musclebones brought closer to together when muscles contract biceps o Extensorbones move further apart when muscles contract triceps o Antagonistic Muscle Groupsneed pairs of muscles to move in both directionsStructureEpimysiumouter connective tissue arranged as each individual muscle fiber Contains bundles of muscle tissue called Fascicleso Covered by the Perimysium a connective tissue sheatho Nerves and blood vessels Muscle fibers muscle cells are found within each fascicleo Covered by an innermost connective tissue sheath Endomysiumo Within the muscle fibers are the functional units of skeletal muscle myofibrils o Contain so many myofibrils that there is little room for other organelles o Cytosol contains many glycogen granules energy storagemitochondria ATP synthesis Structure of a Muscle Fibre FIGURE 123b 124 Long cylindrical cell Several hundred nuclei on the surface of the fibreCell membrane is called the sarcolemmaMajority of the space is taken up by myofibrilso Contractileelastic protein bundles Sarcoplasmic Reticulum SRa specialized ER important for contractionso Associated with this SR are a series of branching tubes called TTubules Transverse tubulesLumen continuous with ECFAllows for the whole cell to contract at once during depolarization 2o Closely associated with the terminal cisternae squester Ca for the contractions
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