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The Muscular System
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The Muscular System

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  • 1. T- 1-855-694-8886Email- info@iTutor.comBy iTutor.com
  • 2.  The muscular system is a complexcollection of tissues, each with a differentpurpose. Understanding the components of themuscular system, including the varioustypes of connective tissues, is a good wayto understand how bodies and physicalmovement work.© iTutor. 2000-2013. All Rights Reserved
  • 3.  Body movement (Locomotion) Maintenance of posture Respiration– Diaphragm and intercostal contractions Communication (Verbal and Facial) Constriction of organs and vessels– Peristalsis of intestinal tract– Vasoconstriction of b.v. and other structures (pupils) Heart beat Production of body heat (Thermogenesis)© iTutor. 2000-2013. All Rights Reserved
  • 4.  Excitability: capacity of muscle to respond to astimulus. Contractility: ability of a muscle to shorten andgenerate pulling force. Extensibility: muscle can be stretched back to itsoriginal length. Elasticity: ability of muscle to recoil to original restinglength after stretched.© iTutor. 2000-2013. All Rights Reserved
  • 5. © iTutor. 2000-2013. All Rights Reserved
  • 6.  Skeletal– Attached to bones– Makes up 40% of body weight– Responsible for locomotion, facial expressions, posture, respiratorymovements, other types of body movement– Voluntary in action; controlled by somatic motor neurons Smooth– In the walls of hollow organs, blood vessels, eye, glands, uterus, skin– Some functions: propel urine, mix food in digestive tract,dilating/constricting pupils, regulating blood flow,– In some locations, auto rhythmic– Controlled involuntarily by endocrine and autonomic nervous systems Cardiac– Heart: major source of movement of blood– Auto rhythmic– Controlled involuntarily by endocrine and autonomic nervous systems© iTutor. 2000-2013. All Rights Reserved
  • 7. © iTutor. 2000-2013. All Rights Reserved
  • 8. Muscle attachments– Most skeletal muscles run fromone bone to another.– One bone will move – otherbone remains fixed.Origin – less movableattachment.Insertion – more movableattachment.© iTutor. 2000-2013. All Rights Reserved
  • 9. Muscle attachments (continued)– Muscles attach to origins and insertions byconnective tissueFleshy attachments – connective tissue fibers areshort.Indirect attachments – connective tissue forms atendon or aponeurosis.– Bone markings present where tendons meetbonesTubercles, trochanters, and crests.© iTutor. 2000-2013. All Rights Reserved
  • 10.  Composed of muscle cells (fibers), connective tissue, bloodvessels, nerves. Fibers are long, cylindrical, and multinucleated. Tend to be smaller diameter in small muscles and larger inlarge muscles. 1 mm- 4 cm in length. Develop from myoblasts; numbers remain constant. Striated appearance. Nuclei are peripherally located.© iTutor. 2000-2013. All Rights Reserved
  • 11. © iTutor. 2000-2013. All Rights Reserved
  • 12.  SR is an elaborate, smooth endoplasmic reticulum– runs longitudinally and surrounds each myofibril– Form chambers called terminal cisternae on either side of the T-tubules A single T-tubule and the 2 terminal cisternae form a triad SR stores Ca++ when muscle not contracting– When stimulated, calcium released into sarcoplasm– SR membrane has Ca++ pumps that function to pump Ca++ out ofthe sarcoplasm back into the SR after contraction© iTutor. 2000-2013. All Rights Reserved
  • 13. © iTutor. 2000-2013. All Rights Reserved
  • 14.  Many elongated myosin molecules shaped like golf clubs. Single filament contains roughly 300 myosin molecules. Molecule consists of two heavy myosin molecules wound togetherto form a rod portion lying parallel to the myosin myofilament andtwo heads that extend laterally. Myosin heads1. Can bind to active sites on the actins molecules to form cross-bridges.(Actin binding site)2. Attached to the rod portion by a hinge region that can bend andstraighten during contraction.3. Have ATPase activity: activity that breaks down adenosinetriphosphate (ATP), releasing energy. Part of the energy is used tobend the hinge region of the myosin molecule during contraction© iTutor. 2000-2013. All Rights Reserved
  • 15. Tropomyosin Tropoin ActinMyosin© iTutor. 2000-2013. All Rights Reserved
  • 16.  Thin Filament: composed of 3 major proteins1. F (fibrous) actin2. Tropomyosin3. Troponin Two strands of fibrous (F) actin form a double helix extending thelength of the myofilament; attached at either end at sarcomere.– Composed of G actin monomers each of which has a myosin-binding site (see yellow dot)– Actin site can bind myosin during muscle contraction. Tropomyosin: an elongated protein winds along the groove of the Factin double helix. Troponin is composed of three subunits:– Tn-A : binds to actin– Tn-T :binds to tropomyosin,– Tn-C :binds to calcium ions.© iTutor. 2000-2013. All Rights Reserved
  • 17.  Cells are not striated Fibers smaller than those in skeletal muscle Spindle-shaped; single, central nucleus More actin than myosin No sarcomeres– Not arranged as symmetrically as in skeletal muscle,thus NO striations. Caveolae: indentations in sarcolemma;– May act like T tubules Dense bodies instead of Z disks– Have noncontractile intermediate filaments© iTutor. 2000-2013. All Rights Reserved
  • 18. © iTutor. 2000-2013. All Rights Reserved
  • 19. Grouped into sheets in walls of hollow organs. Longitudinal layer – muscle fibers run parallel to organ’slong axis. Circular layer – muscle fibers run around circumference ofthe organ. Both layers participate in peristalsis.© iTutor. 2000-2013. All Rights Reserved
  • 20.  Found only in heart where it forms a thick layer calledthe myocardium. Striated fibers that branch Each cell usually has one centrally-located nucleus Fibers joined by intercalated disks– IDs are composites of desmosomes and gap junctions– Allow excitation in one fiber to spread quickly to adjoiningfibers Under control of the ANS (involuntary) and endocrinesystem (hormones) Some cells are autorhythmic– Fibers spontaneously contract (aka Pacemaker cells)© iTutor. 2000-2013. All Rights Reserved
  • 21. © iTutor. 2000-2013. All Rights Reserved
  • 22. The endCall us for moreInformation:www.iTutor.com1-855-694-8886Visit