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Module 3.docx - Muscular System Types of Muscle 3 types:...

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Muscular SystemTypes of Muscle3 types: cardiac, smooth, and skeletalEach muscle is a distinct organ composed of skeletal muscle tissue, bloodvessels, tendons, and nervesMuscle tissue acts to move substances throughout the body and can be foundin the heart, digestive organs, and blood vesselsSmooth muscle is controlled by the nervous system or hormones. It mayeither be generally inactive and then respond to stimulation, or it may berhythmicSkeletal muscles help the human body move. Most skeletal; muscle isattached to bones via tendonsCardiac muscle is found on the heart. It contracts rhythmically, modulated byneural activity and hormonesMuscles can be characterized based on their morphology or how theyfunctionMorphological:oSmooth muscle: fusiform cells with no striations and centrally locatednucleus within the cell. Smooth muscle is found in blood vessels, thedigestive system, and other visceraoStriated muscle: marked by both light and dark bans in appearanceSkeletal: striations, long muscle fibers, multinucleated cells.Peripherally located nucleus within a cellCardiac: intercalated discs, striations. Centrally located nucleuswithin cells.Functional:oVoluntary muscle: consciously controlled in order to perform aspecific function. Skeletal muscle is voluntaryoInvoluntary muscle: not consciously controlled. Consists of smoothmuscle and cardiac muscleMuscle has 2 basic properties:oExcitability: muscle tissue receives electrical signals from nerves orstimulation from hormones to contractoContractility: when a muscle cell is activated by a nerve or stimulatedby a hormone (when excited) this causes the muscle to shorten,resulting in contractionSkeletal MuscleThe only voluntary muscle tissue in the human body, meaning it is controlledconsciouslyEvery physical action that a person consciously performs requires skeletalmuscleAttached to the bones of the skeletal system are about 700 named musclesthat account for roughly half of a person’s body weight
Each of these muscles is a discrete organ composed of skeletal muscle tissue,epithelial, connective, and nervous tissueSkeletal muscle contracts to move parts of the bodyMost skeletal muscles are attached to 2 bones across a joint, so the musclebrings parts of those 2 bones closer to each otherSkeletal muscle functions to:oProduce movementoMaintain posture and stabilize jointsoControl excretion and swallowingoProduce heatConsists of muscle tissue and connective tissueThe connective tissue surrounds the muscle tissue and attaches the ends ofeach muscle to boneConnective tissue in skeletal muscle is categorized into 3 layers:oEpimysium: the layer of connective tissue that surrounds an entiremuscle and is continuous with the tissue that becomes the tendonoPerimysium: surrounding a bundle of muscle fibres (fascicle) within amuscleoEndomysium: surrounds individual muscle cells (muscle fibre) withina muscle bundleWithin a muscle cell (myofiber), there are many myofibers that containnumerous myofilaments, the units of contraction for the muscle cellMuscle cell:1.

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