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The Muscular System

The Muscular System. J. Hinson Human Anatomy and Physiology JCHS. I. Introduction. The human body has over 400 skeletal muscles, which accounts for ~ 50 % of the body weight! Muscles are generally named for their location , size , direction of fibers, or number of attachments.

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The Muscular System

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  1. The Muscular System J. Hinson Human Anatomy and Physiology JCHS

  2. I. Introduction • The human body has over 400skeletal muscles, which accounts for ~ 50% of the body weight! • Muscles are generally named for their location, size, direction of fibers, or number of attachments. • The gluteus maximus is the largest muscle in the body. • The strongest muscle in the body is the masseter.

  3. II. Some Key Terms • origin: muscle attachment on immovable bone; usually proximal • insertion: muscle attachment on movable bone; usually distal • prime mover: major contractile muscle producing movement • synergist: muscle assisting PM • antagonist: muscle stretched when PM contracts

  4. Major Muscle Groups

  5. III. Functions - Characteristics • Contractility: ability to shorten** • Excitability: (responsiveness or irritability) ability to receive and respond to stimuli • Extensibility: ability to be stretched or extended • Elasticity: ability to recoil after stretch

  6. III. Functions - General • PROVIDES FOR MOVEMENT via contraction of fibers • Maintaining posture • Stabilizing joints • Generating heat • Protect internal organs

  7. IV. Types • Voluntary (skeletal) • Attached to bone • Controlled by the individual • Responsible for body movements http://www.medical-look.com/systems_images/Muscular_System.jpg

  8. IV. Types • Voluntary (skeletal) • Wrapped in layers of connective tissue called fascia • Fascia merges to form a tendon (connects two!) http://www.ditchfieldpt.com/assets/fascia_1244463_white.jpg http://www.eorthopod.com/images/ContentImages/foot/foot_achilles/foot_achilles_tendon_anatomy01a.jpg

  9. IV. Types • Smooth (involuntary) • Found in walls of digestive and urinary system • Found in blood vessels and bronchi http://webanatomy.net/histology/muscle/smooth_muscle_arrangement.jpg

  10. IV. Types • Cardiac (Involuntary) • Found only in the heart • Can go without blood for only a short time http://webanatomy.net/histology/cardiac/cardiac_muscle.jpg http://eduspace.free.fr/vs_pages/bionic_heart_fichiers/real_heart.jpg

  11. V. Structures • Epimysium: “overcoat” of dense irregular connective tissue surrounding entire muscle • Perimysium: fibrous connective tissue surrounding each fascicle • Endomysium: reticular connective tissue surrounding each individual muscle fiber

  12. V. Structures • Muscle: organ • Fascicle: bundle of muscle cells • Muscle fiber: striated cell; covered by sarcolemma (membrane) • Myofibril: rod-like contractile unit of muscle fiber • Sarcomere: contractile unit of a myofibril • Tendon/Aponeurosis: connective tissue wrapping extending from muscle

  13. SLIDING FILAMENT THEORY J. Hinson Human Anatomy and Physiology JCHS

  14. I. The Neuromuscular Junction • Connection b/w nerve and muscle fiber • In response to a motor nerve impulse, the end of a motor nerve secretes a neurotransmitter, Acetylcholine (ACh), which stimulates a muscle fiber.

  15. 1. http://academic.wsc.edu/faculty/jatodd1/351/motor_unit.jpg

  16. http://camilolab.slu.edu/444/graphics/Leeson6-12.jpg

  17. I. The Neuromuscular Junction C. Threshold stimulus – minimal stimulus needed to cause a muscular contraction 1.“all or none” response http://www.bbraunusa.com/stimuplex/graphics/hi_speed_nerve.jpg

  18. II. Skeletal Muscle Contraction • Muscle fiber contraction results from actin sliding over myosin. • The SARCOMERE is the structural and functional unit of the muscle. http://www.3dotstudio.com/zz.html

  19. http://www.ucl.ac.uk/~sjjgsca/MuscleSarcomere.gif Myosin Actin

  20. http://www.peprotech.com/uploadedimages/Sarcomere2.jpg

  21. http://gilead.org.il/hcm/sarcomere.jpg

  22. II. Skeletal Muscle Contraction Contraction Animation:http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__action_potentials_and_muscle_contraction.html • Contraction Stimulus • Acetylcholine stimulates. • Nerve impulse travels over the mm. fiber surface and via transverse tubules into fiber. • Sarcoplasmic reticulum releases Ca2+. • Cross-bridge forms b/w filaments, and actin moves inward causing the muscle to shorten.

  23. http://www.ivy-rose.co.uk/Topics/Muscles/Sliding-Filament_Theory.jpghttp://www.ivy-rose.co.uk/Topics/Muscles/Sliding-Filament_Theory.jpg

  24. II. Skeletal Muscle Contraction • Contraction Stimulus 5. Fiber relaxes w/ uptake of Ca2+. 6. Cholinesterase decomposes ACh. 7. Actin-myosin cross-bridge breaks. 8. Muscle fiber relaxes. Myofilament Contraction: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__myofilament_contraction.html Sarcomere Contraction Animation:http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__sarcomere_contraction.html

  25. http://www.octc.kctcs.edu/GCaplan/anat/Notes/API%20Notes%20J%20%20Muscle%20Contraction.htmhttp://www.octc.kctcs.edu/GCaplan/anat/Notes/API%20Notes%20J%20%20Muscle%20Contraction.htm

  26. II. Skeletal Muscle Contraction • ATP supplies the energy for mm. fiber contraction, and creatine phosphate stores energy that can be used to synthesize ATP. ** Contraction will sustain as long as enough ATP and Ca2+ is available!

  27. II. Skeletal Muscle Contraction D. Other responses • Twitch: short, single contraction • Sustained contraction: rapid succession of twitches (fluid movement). • Tetany: forceful, sustained contraction • Muscle tone: minimal sustained contraction (Posture!) • Myogram: recording of muscle contraction

  28. http://media.wiley.com/Lux/05/21805.nfg002.jpg

  29. III. Muscular Response to Exercise • Myoglobin: mm. cell protein that stores Oxygen • Oxygen supply is sufficient at rest or during moderate exercise to support aerobic respiration. 1. Energy released is lost as heat.

  30. III. Muscular Response to Exercise C. During vigorous exercise, an O2 deficiency may develop, and lactic acid may be produced, thus DOMS (delayed onset muscle soreness). • Lactic acid accumulation responsible for fatigue. D. Oxygen Debt – O2 needed to convert LA to glucose and restore ATP and CP

  31. http://img.sparknotes.com/figures/1/18b9012870c85fba3a8046a767b52ddf/anaerobicaerobic.gifhttp://img.sparknotes.com/figures/1/18b9012870c85fba3a8046a767b52ddf/anaerobicaerobic.gif

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