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Neuromuscular Fundamentals

Neuromuscular Fundamentals. Anatomy and Physiology of Human Movement 420:050. Outline. Introduction Structure and Function Fiber Arrangement Muscle Actions Role of Muscles Neural Control Factors that Affect Muscle Tension. Introduction.

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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 • Fiber Arrangement • Muscle Actions • Role of Muscles • Neural Control • Factors that Affect Muscle Tension

  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 • Fiber Arrangement • Muscle Actions • Role of Muscles • Neural Control • Factors that Affect Muscle Tension

  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. Nervous System Structure • Organization • Brain • Spinal cord • Nerves • Fascicles • Neurons Figure 12.2, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings. Figure 12.7, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  10. Nervous System Structure • Both sensory and motor neurons in nerves Figure 12.11, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

  11. Nervous System Structure • The neuron: Functional unit of nervous tissue (brain, spinal cord, nerves) • Dendrites: Receptor sites • Cell body: Integration • Axon: Transmission • Myelin sheath: Protection and speed • Nodes of Ranvier: Saltatory conduction • Terminal branches: Increased innervation • Axon terminals: Connection with muscular system • Synaptic vescicles: Delivery mechanism of “message” • Neurotransmitter: The message

  12. Dendrites Cell body Axon Myelin sheath Node of Ranvier Terminal ending Terminal branch Figure 12.4, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

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

  14. Figure 12.19, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

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

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

  17. 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

  18. 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

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

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

  21. 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

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

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

  24. 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

  25. 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

  26. 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

  27. 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.

  28. 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.

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

  30. +30 mV -70 mV

  31. 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

  32. 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

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

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

  35. 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

  36. Ach

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

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

  39. 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

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

  41. CALCIUM RELEASE Sarcolemma

  42. 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

  43. Coupling of Actin and Myosin • Tropomyosin • Troponin

  44. Blocked Coupling of actin and myosin

  45. 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

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

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

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

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

  50. 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

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