Anatomy and Physiology Objectives Exam 1 Muscular System and Review 1 Define and identify the anatomy of the skeletal muscle and explain sliding filament theory leading to muscle contraction a The skeletal muscle is a connective tissue composed of thousands of muscle fibers and functions to produce movement maintain posture stabilize joints and generate heat Skeletal muscles functional characteristics are excitability contractility extensibility elasticity b The connective tissue of a skeletal muscle is composed of an outer layer known as the epimysium The epimysium contains fascicles whose outer layer is known as the perimysium Within each fascicle the endomysium is wrapped around each muscle fiber c Myofibers are composed of two types of filaments Thick filaments composed of bundles of myosin and thin filaments composed of strands of actin and have regulatory proteins tropomyosin and troponin d Sarcolemma plasma membrane basement membrane fuses with the tendon bone myoglobin e Sarcoplasm cytoplasm contains proteins minerals fats organelles glycogen f Transverse Tubules transport system deep into fiber allows rapid conduction of impulse Infoldings of the sarcolemma that conduct electrical impulses from the surface of the cell to the terminal cisternae g Sarcoplasmic Reticulum is a smooth endoplasmic reticulum surrounding each myofibril myofibrils account for roughly 80 of cellular volume SR is also a membranous channel parallel to myofibril and storage site for Calcium h Sarcomere the portion of a fiber between two Z discs Z discs are also known as I bands think filaments only Sarcomere is the smallest contractile unit of the skeletal myofiber i A Band dark band ii I band light band iii H zone central region of the A band where there is no thick and thin filament overlap H zone is bisected by the M line iv M line composed of proteins that keep the sarcomere in proper spatial orientation as it lengthens and shortens v Z discs are the most dense i Contractile Proteins Myosin and Actin i Actin G Actin globular actin actin monomers F Actin filamentous actin G Actins polymerize into F Actin and are arranged in a double helix j Regulatory proteins Tropomyosin and Tropnin together produce contraction k Structural Proteins C Protein part of thick filament involved in holding the tails of myosin in a correct spatial arrangement Titin links the end of the thick filament to the z disc l Sliding Filament Theory Actin and myosin filaments slide past one another shortening the sarcomere Myofilaments do no change in length just overlap to shorten sarcomere Myosin at rest has ADP Pi attached at the myosin heads Calcium released from SR bind to troponin causing tropomysoin to move and open up binding site on actin myofilaments Single Pi on myosin gets removed so myosin can attach to binding site on Actin forming cross bridge ADP is then expended in what is called the power stroke when myosin heads pull the actin inwards Once ADP is spent ATP attaches to myosin heads which triggers release of myosin from Actin binding sites and are broken down into ADP Pi as heads move back into resting position recovery stroke If Ca is still present cycle will repeat until sarcomere is shortened until Ca is transported back into SR and the muscle relaxes m Step of Muscle Contraction i Neuron AP arrives at the end of motor neuron ii Acetylcholine is released enters synaptic cleft iii ACH binds to receptors on motor end plates iv Sodium ions rush into muscle fibers v Muscle AP sweeps into T tubules invaginations in membrane vi SR releases Calcium vii Calcium binds to troponin viii When Ca binds to Ca it causes tropomyosin to move and expose myosin binding site ix Myosin binds to actin x Myosin pivots pulling actin filaments xi Myosin releases from actin xii Myosin re extends into ready rest position 2 Define and distinguish between the types of muscle fibers and explain the possibilities or lack thereof of fiber type morphology a Three types of muscle fibers I IIa IIx i Type I Red Slow function in antigravity weight bearing and sustained movement Slow contraction time small motor neuron fatigue resistant aerobic can last for hours low force production high mitochondrial and capillary density high oxidative capacity low glycolytic capacity and triglycerides are major storage fuel ii Type IIa Pink Fast oxidative function in sustained locomotion Moderately fast contraction time medium size motor neuron fairly high resistance to fatigue long term anaerobic duration less than 30 minutes medium force production high mitochondrial density oxidative capacity glycolytic capacity intermediate capillary density creatine phosphate and glycogen are major storage fuels iii Type IIx IIb White Fast oxidative glycolytic function in power movements Fast Very fast contraction time large motor neurons intermediate low resistance to fatigue short term anaerobic duration less than 5 minutes high very high force production medium low mitochondrial density low capillary density intermediate low oxidative capacity high glycolytic capacity creatine phosphate and glycogen are major storage fuels b Fiber type morphology can occur during loading and unloading i Loading exercise training IIx IIa ii Unloading space flight spinal cord injury I IIa IIx 3 State the different types of skeletal muscle contraction and the functions and characteristics of skeletal muscle a Skeletal muscle contraction types b Functions of skeletal muscles Produce movement maintain posture stabilize c Characteristics of skeletal muscles excitability contractility extensibility 4 What are the different types of fascicle arrangements Also what determines a muscles joints generate heat elasticity power and ROM a Fascicle arrangements i Circular arranged in rings Orbicularis Oris Eye ii Convergent Broad origin and fascicles converge towards insertion Pectoralis major Origin sternum clavicle Insertion tendon of humerus Converges towards humerus iii Parallel fascicles run parallel along the axis longest muscle Sartorius iv Fusiform spindle shaped biceps brachii v Pennate attach obliquely to the central tendon featherlike 1 Unipennate extensor digitorum longus 2 Bipennate rectus femorus 3 Multipennate delts a Looks like many feathers b Determining Muscle Power and ROM i Muscles with the greatest number of fibers have the most power 1 Bipennate rectus femorus and Multipennate delts are pound for pound the strongest muscles ii Parallel fascicle arrangement muscles that shorten
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