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Neuromuscular Fundamentals

Introduction to the structure and function of muscles and the neural control of movement. Covers the role of muscles in movement, protection, posture, and heat production. Explores the properties of muscle tissue and the structure and function of the nervous and muscular systems. Describes the process of nerve impulse transmission and the release of neurotransmitters. Includes a detailed explanation of the sliding filament theory and the coupling of actin and myosin.

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Neuromuscular Fundamentals

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  1. Neuromuscular Fundamentals Anatomy and Physiology of Human Movement 420:050

  2. Outline • Introduction • Structure and Function • Muscle Actions • Role of Muscles • Neural Control

  3. Introduction • Responsible for movement of body and all of its joints • Muscles also provide • Protection • Posture and support • Produce a major portion of total body heat • Over 600 skeletal muscles comprise approximately 40 to 50% of body weight • 215 pairs of skeletal muscles usually work in cooperation with each other to perform opposite actions at the joints which they cross • Aggregate muscle action - muscles work in groups rather than independently to achieve a given joint motion

  4. Muscle Tissue Properties • Irritability or Excitability - property of muscle being sensitive or responsive to chemical, electrical, or mechanical stimuli • Contractility - ability of muscle to contract & develop tension or internal force against resistance when stimulated • Extensibility - ability of muscle to be passively stretched beyond it normal resting length • Elasticity - ability of muscle to return to its original length following stretching

  5. Outline • Introduction • Structure and Function • Muscle Actions • Role of Muscles • Neural Control

  6. Structure and Function • Nervous system structure • Muscular system structure • Neuromuscular function

  7. Figure 14.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  8. Nervous System Structure • Integration of information from millions of sensory neurons  action via motor neurons Figure 12.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  9. Figure 12.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings. Terminal ending Synaptic vescicle Neurotransmitter: Acetylcholine (ACh)

  10. Structure and Function • Nervous system structure • Muscular system structure • Neuromuscular function

  11. Classification of Muscle Tissue • Three types: 1. Smooth muscle 2. Cardiac muscle 3. Skeletal muscle

  12. Skeletal Muscle: Properties • Extensibility: The ability to lengthen • Contractility: The ability to shorten • Elasticity: The ability to return to original length • Irritability: The ability to receive and respond to stimulus

  13. Muscular System Structure • Organization: • Muscle (epimyseum) • Fascicle (perimyseum) • Muscle fiber (endomyseum) • Myofibril • Myofilament • Actin and myosin • Other Significant Structures: • Sarcolemma • Transverse tubule • Sarcoplasmic reticulum • Tropomyosin • Troponin

  14. Figure 10.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  15. Figure 10.4, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  16. http://staff.fcps.net/cverdecc/Adv%20A&P/Notes/Muscle%20Unit/sliding%20filament%20theory/slidin16.jpghttp://staff.fcps.net/cverdecc/Adv%20A&P/Notes/Muscle%20Unit/sliding%20filament%20theory/slidin16.jpg

  17. Figure 10.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  18. Structure and Function • Nervous system structure • Muscular system structure • Neuromuscular function

  19. Neuromuscular Function • Basic Progression: 1. Nerve impulse 2. Neurotransmitter release 3. Action potential along sarcolemma 4. Calcium release 5. Coupling of actin and myosin 6. Sliding filaments

  20. Nerve Impulse • What is a nerve impulse? -Transmitted electrical charge -Excites or inhibits an action -An impulse that travels along an axon is an ACTION POTENTIAL

  21. Nerve Impulse • How does a neuron send an impulse? -Adequate stimulus from dendrite -Depolarization of the resting membrane potential -Repolarization of the resting membrane potential -Propagation

  22. Nerve Impulse • What is the resting membrane potential? -Difference in charge between inside/outside of the neuron -70 mV Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  23. Nerve Impulse • What is depolarization? -Reversal of the RMP from –70 mV to +30mV Propagation of the action potential Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  24. Nerve Impulse • What is repolarization? -Return of the RMP to –70 mV Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  25. +30 mV -70 mV

  26. Neuromuscular Function • Basic Progression: 1. Nerve impulse 2. Neurotransmitter release 3. Action potential along sarcolemma 4. Calcium release 5. Coupling of actin and myosin 6. Sliding filaments

  27. Release of the Neurotransmitter • Action potential  axon terminals 1. Calcium uptake 2. Release of synaptic vescicles (ACh) 3. Vescicles release ACh 4. ACh binds sarcolemma

  28. Figure 12.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings. Ca2+ ACh

  29. Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  30. Neuromuscular Function 1. Nerve impulse 2. Neurotransmitter release 3. Action potential along sarcolemma 4. Calcium release 5. Coupling of actin and myosin 6. Sliding filaments

  31. Ach

  32. AP Along the Sarcolemma • Action potential  Transverse tubules 1. T-tubules carry AP inside 2. AP activates sarcoplasmic reticulum

  33. Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  34. Neuromuscular Function 1. Nerve impulse 2. Neurotransmitter release 3. Action potential along sarcolemma 4. Calcium release 5. Coupling of actin and myosin 6. Sliding Filaments

  35. Calcium Release • AP  T-tubules  Sarcoplasmic reticulum 1. Activation of SR 2. Calcium released into sarcoplasm

  36. CALCIUM RELEASE Sarcolemma

  37. Neuromuscular Function 1. Nerve impulse 2. Neurotransmitter release 3. Action potential along sarcolemma 4. Calcium release 5. Coupling of actin and myosin 6. Sliding filaments

  38. Coupling of Actin and Myosin • Tropomyosin • Troponin

  39. Blocked Coupling of actin and myosin

  40. Neuromuscular Function 1. Nerve impulse 2. Neurotransmitter release 3. Action potential along sarcolemma 4. Calcium release 5. Coupling of actin and myosin 6. Sliding filaments

  41. Sliding Filament Theory • Basic Progression of Events 1. Cross-bridge 2. Power stroke 3. Dissociation 4. Reactivation of myosin

  42. Cross-Bridge • Activation of myosin via ATP -ATP  ADP + Pi + Energy -Activation  “cocked” position

  43. Power Stroke • ADP + Pi are released • Configurational change • Actin and myosin slide

  44. Dissociation • New ATP binds to myosin • Dissociation occurs

  45. Reactivation of Myosin Head • ATP  ADP + Pi + Energy • Reactivates the myosin head • Process starts over • Process continues until: -Nerve impulse stops -AP stops -Calcium pumped back into SR -Tropomyosin/troponin back to original position

  46. Outline • Introduction • Structure and Function • Muscle Actions • Role of Muscles • Neural Control

  47. Muscle Actions: Terminology • Origin (Proximal Attachment): • Structurally, the proximal attachment of a muscle or the part that attaches closest to the midline or center of the body • Functionally & historically, the least movable part or attachment of the muscle • Note: The least movable may not necessarily be the proximal attachment

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