8. Muscle Tissue and Physiology.pdf - 3/19/2020 Human...

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3/19/20201Human Anatomy and Physiology I:Muscle Tissue and PhysiologyFocusing Primarily on Skeletal Muscleand Smooth MuscleFunctions of Muscle TissueFunctional characteristics of allmuscle tissues:Excitability(electrical)the ability to receive and respond toan electrochemical stimulus; some muscle cells can generatean action potential (such as certain types of cardiac andsmooth muscle cells).Contractilitythe ability to shorten when an adequatestimulus is present (separates muscle from all other tissues);possess a highly specialized cytoskeleton for generation offorce; requires calcium ions for contraction.Extensibilitythe ability to be stretched or extended (due tothe relaxation of the myofibrils).Elasticitythe ability of a muscle to resume resting lengthafter it has contracted or been stretched (probably due topassive tension from the connective tissues).
3/19/20202Functions of Skeletal Muscle TissueMovement/locomotion:Most voluntary movements are due to skeletal muscularcontraction; with the exception of amoeboid, ciliary, andflagellar movements.Posture Maintenance:Due to posture containing muscles, such as the soleus anderector spinae muscles.Stabilizing Joints:Increasing the muscle tone (therestinglevels of contraction)will stabilize joints.Heat Generation:About 50% of the energy from ATP hydrolysis is heat energy.Skeletal muscle is most important; about 40% of body mass.Introduction to Skeletal Muscle TissueThere are three different types of muscle tissues:1) skeletal, 2) cardiac, and 3) smooth.Individual musclecellsare also calledfibers.Skeletal Muscle Tissue:Typically, has the longest fibers (unbranched) and composes 40% of the total bodymass.Multinucleated cells (derived from unicellular precursor cells that fuse) or fibers.Striated(myofibrils/contractile machinerythe myofilamentsare regularly arrangedto show bands, layers, or lines).Often called “voluntary muscle;” controlled by thesomatic nervous system.Can contract rapidly and vigorously, but tires easily (when compared to cardiac andsmooth muscles).
3/19/20203Gross Anatomy of a Skeletal MuscleA skeletal muscle is a discreet organ.Each muscle also contains substantial amounts of connective tissue, bloodvessels, and nerve fibers.There are probably over 600 skeletal muscles in the body.Each skeletal muscle is typically composed of hundreds tothousands of muscle cells (or fibers); however, this is variable.Skeletal muscles develop embryonically by fusion of manyuninucleatemyoblasts.Anatomy of a Skeletal MuscleEach fiber is surrounded by a thin basal lamina with a loss mesh ofreticular fibers; this wrapping called theendomysium.Between the endomysium and the muscle fibers are scatteredsatellite cells.

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JONES
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Skeletal Muscle Tissue

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