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Muscle Tissue Handout #5 Muscles and #6 Excitation-Contraction

A. Types of muscle B. Functions of muscle C. Characteristics of muscle D. Anatomy and innervation of skeletal muscle tissue 1. Nerve and blood supply 2. Connective tissue components 3. The motor unit 4. The neuromuscular junction

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Muscle Tissue Handout #5 Muscles and #6 Excitation-Contraction

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  1. A. Types of muscle B. Functions of muscle C. Characteristics of muscle D. Anatomy and innervation of skeletal muscle tissue 1. Nerve and blood supply 2. Connective tissue components 3. The motor unit 4. The neuromuscular junction 5. Microscopic anatomy of muscle a. Myofibrils b. Sarcoplasmic reticulum and transverse tubules E. Contraction of skeletal muscle 1. Sliding filament mechanism a. Role of calcium and regulator proteins b. The power stroke and the role of ATP 2. Relaxation 3. Muscle tone 4. Homeostasis of body temperature F. Adjusting muscle tension 1. Twitch 2. Frequency of stimulation a. Tetanus b. Staircase effect (treppe) 3. Number of muscle cells contracting 4. Isotonic and isometric contractions G. Cardiac muscle H. Smooth muscle Muscle TissueHandout #5 Muscles and #6 Excitation-Contraction

  2. Motion results from alternating contraction (shortening) and relaxation of muscles. The prime function of muscle is to: • convert chemical energy (ATP) into mechanical energy in order to: • 1. generate force • 2. perform work • 3. produce movements

  3. Types of Muscle Tissue • 1. skeletal muscle • 2. cardiac muscle • 3. smooth muscle

  4. Functions of Muscle Tissue • 1. motion • 2. stabilizing body positions and regulating organ volume • 3. thermogenesis

  5. Characteristics of Muscle Tissue • 1. excitability (irritability) • 2. contractility • 3. extensibility • 4. elasticity

  6. Anatomy of Skeletal Muscle • Blood supply and innervation of skeletal muscle tissue

  7. Fascia • 1. superficial • 2. deep Deep Fascia Superficial fascia

  8. Connective Tissues of Skeletal Muscle • 1. epimysium • 2. perimysium -- fascicles • 3. endomysium _______________ • 4. tendon • 5. tendon sheath • 6. aponeurosis

  9. Microscopic Anatomy • 1. myofiber • 2. sarcolemma • 3. sarcoplasm • 4. myofibrils • 5. myofilaments • 6. sarcomeres

  10. Skeletal Muscle Anatomy Summary

  11. Sarcomere • 1. Z disc • 2. thin and thick myofilaments • 2. A bands and I bands • 3. striations

  12. Thin Myofilament • 1. actin a. actin filaments (2) b. myosin-binding sites • 2. tropomyosin • 3. troponin _______________________ • 4. tropomyosin-troponin complex

  13. Thick Myofilament • 1. myosin • 2. filamentous tail (shaft) • 3. globular head (cross bridge) ___________________ • 4. titan (elastin filament)

  14. Sarcoplasmic Reticulum • 1. intracellular tubules • 2. stores Ca++ at rest • 3. releases Ca++ when stimulated • 4. Ca++ diffuse into sarcoplasm

  15. Transverse Tubules • 1. tunnel-like infoldings of sarcolemma • 2. lie at right angles to myofibrils • 3. filled with ECF • 4. terminal cisternae • 5. muscle triad

  16. The Nerve Muscle Relationship • 1. motor neuron • 2. motor unit • 3. precise vs gross control • 4. What is recruitment?

  17. The Neuromuscular Junction • 1. axon terminals • 2. synapse and synaptic cleft • 3. motor end plate • 4. synaptic vesicles • 5. neurotransmitter = acetylcholine (ACh) • 7. exocytosis • 8. ACh receptors on motor end plate

  18. Neuromuscular Junction

  19. Excitation-Contraction Coupling • Sliding filament theory • 1. thick myofilaments attach to thin myofilaments • 2. cross bridges "tilt" or swivel • 3. thin myofilaments "slide" across thick myofilaments • 4. Z discs are drawn together • 5. sarcomeres shorten

  20. Sliding filament theory

  21. Excitation-Contraction Coupling

  22. Power Stroke • 1. ACh stimulates motor end plate • 2. action potential crosses sarcolemma, T-tubules, and sarcoplasmic reticulum • 3. Ca++ channels open a. Ca++ bind T-T complex b. Ca++ activate ATPase • 4. cross bridges bind and swivel

  23. Cross Bridge Cycle

  24. Recovery stroke (muscle relaxation) • acetylcholinesterase • calsequestrin

  25. Summary of Muscle Contraction

  26. Muscle Tone • 1. sustained, small contractions of motor units • 2. few motor units contracting, others relaxed • 3. muscle firmness without producing movement • 4. essential for maintaining posture • 5. asynchronous firing of motor units

  27. Muscle Metabolism During Contraction • 1. aerobic • 2. phosphagen • 3. glycogen-lactic acid

  28. Phosphagen System

  29. What is oxygen debt? • The difference between oxygen consumption at rest and oxygen consumption following exercise. This "debt" must be "repaid" in order to: • 1. replace the body's oxygen reserves • 2. replenish the phosphagen system • 3. oxidize accumulated lactic acid • 4. serve the elevated metabolic rate post-exercise

  30. Physiological Classes of Muscle Fibers • 1. slow oxidative, slow-twitch, red, or type I fibers abundant mitochondria, myoglobin, and capillaries aerobic respiration • 2. fast glycolytic, fast-twitch, white, or type II fibers poor in mitochondria, myoglobin, and capillaries rich in enzymes of the phosphagen and glycogen pathways vast sarcoplasmic reticulum (rapid Ca++ movement) anaerobic respiration fatigue quickly • 3. intermediate fibers (at least 3 types)

  31. Homeostasis of Body Temperature • Controlled Condition- A stimulus or stress disrupts homeostasis by causing body temperature to decrease below normal. • Receptors-Thermoreceptors, located in the skin and in the hypothalamus, detect the decreased body temperature and provide nervous input to the hypothalamus. • Control Center- The hypothalamic temperature control center integrates the input, then provides output that leads to stimulation of skeletal muscles. • Effectors- In response, large skeletal muscle groups increase their muscle tone involuntarily (shivering). • Return to Homeostasis- Due to the inefficient use of energy by contracting skeletal muscles, heat is generated, the body temperature increases, and the negative feedback loop turns off the shivering. .

  32. BODY TEMPERATURE CONTROL negative feedback CONTROLLED CONDITION A stimulus or stress disrupts homeostasis by causing a decrease in body temperature RETURN TO HOMEOSTASIS Due to inefficient use of energy by contracting skeletal muscles, heat generated raises body temperature RECEPTOR Thermoreceptors in skin and hypothalamus are activated and send nerve impulses to the control center EFFECTORS Large skeletal muscle groups increase their muscle tone involuntarily (shivering) CONTROL CENTER Hypothalamic control center initiates nerve impulses that lead to stimulation of skeletal muscles end

  33. Regulation of Body Temperature

  34. Behavior of Whole Muscles Adjusting muscle tone • 1. all-or-none principle • 2. threshold stimulus

  35. Adjusting muscle tone -- The amount of force (tension) that a muscle can generate depends upon four factors: • 1. frequency of stimulation of muscle fibers by motor neurons • 2. length of muscle fibers before they contract • 3. number of muscle fibers contracting at any one time (number of activated motor units) -- process of recruitment • 4. structural components of the muscle itself

  36. Length Tension Relationship

  37. Twitch Contractions • 1. latent period • 2. contraction period • 3. relaxation period • 4. refractory period

  38. Treppe contractions(staircase phenomenon)

  39. Wave Summation • 1. incomplete tetany • 2. complete tetany

  40. Isotonic versus Isometric Contratctions

  41. Cardiac Muscle • 1. striated • 2. single nucleus/cell • 3. intercalated discs • 4. functional syncytium • 5. involuntary • 6. self-stimulating

  42. Smooth Muscle • 1. non-striated • 2. no sarcomeres • 3. single nucleus/cell • 4. two types a. visceral (functional syncytium) b. multiunit

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