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Motor Lectures - Central Pattern Generators

Anna mph Neurophysiology Degree Inglés 66 fichas

Fichas del conjunto (66)

  1. 1Where do locomotion pathways originate? (2)Mesencephalic locomotor region (MLR)
    Lateral Hypothalamus
  2. 2What is the step between higher brain centres and the spinal cord in locomotion?Reticulospinal neurons
  3. 3Where are central pattern generators located?Spinal Cord
  4. 4What role do activated muscles provide in locomotion (in terms of CPGs)Resist stretch and provide length/velocity feedback control.
  5. 5What provides load compensation in movements?Golgi tendon organ reflexes and other afferents.
  6. 6What/when can CPGs be adjusted?At stance-swing-stance transitions sensory input can adjust or override CPGs.
  7. 7What (and when) did T. Graham Brown say about locomotion?1911 - Basic pattern of stepping can be produced by the spinal cord without the need of descending commands from the cortex.
  8. 8What did Wilson et al determine about locomotion? When?1967 - Isolated locus nervous system could produce rhythmic output which resembled flying.
  9. 9What is a Central Pattern Generator?Biological neural network.
  10. 10What do CPGs produce? What type of functions do they serve?Produce rhythmic outputs without sensory feedback or central input.
    Oscillatory functions - movement, breathing etc.
  11. 11Describe a simplified spinal circuit of a CPG.Excitatory interneurons each in their own circuit feeding into opposing muscle pairs. Excitatory interneurons connected to each other by inhibitory interneurons so that activation of one excitatory interneuron interneuron switches off the other. Inhibitory interneuron feeds back onto itself disinhibiting the previously switched of excitatory interneuron.
  12. 12How was CPG shown in locust (Waldron)?Isolated nervous system - nerves which would have innervated elevator and depressor wing muscles fire antagonistically in a rhythmic pattern.
    PREPARATION LACKS SENSORY INPUT (DEAFFERENTED) BUT STILL ABLE TO GENERATE RHYTHMIC FLIGHT MOTOR PATTERNS.
  13. 13How do speed, force output and frequency all relate in terms of movement?Increasing frequency (wing-beat) increases force output which leads to an increase in speed.
  14. 14What is the function of the TIMER in CPGs? What can it be formed from?Generates step cycles of varying durations.
    -- Coupled oscillators, such as interneurons.
  15. 15What is the function of the PATTERN FORMATION LAYER?Selects and grades the activation of motor pools.
  16. 16How can the step cycle frequency be increased?Increase the neural drive from the MLR to the CPG
  17. 17What is neuromechanical tuning? What is the point?In well-predicted movements, CPG-generated phase durations and muscle forces closely match those required by evolving biomechanical movements. Less fine tuning and sensory input required.
  18. 18What type of locomotion was shown in a cat with a spinal cord transection? Why?Fictive locomotion. Step cycle still apparent, but not true locomotion as the movements can't be fine tuned (no descending commands or sensory feedback due to spinal cord transection).
  19. 19How do descending commands, sensory feedback and spinal cord intrinsic circuits all fit into CPGs?Descending commands and sensory feedback not necessary (cat + locust).
    Spinal cord intrinsic circuits are essential but also modifiable by descending commands and sensory feedback.
  20. 20Why might CPGS need to be modulated?To meet the requirements of an organism's internal or external surroundings.
  21. 21What are the different types of neuromodulation of CPGs? (3)1) Modulation as part of normal activity
    2) Modulation changes functional configuration to produce different types of motor output.
    3) Changes in neuron complement by switching neurons between circuits and fusing formerly separate networks into larger entities.
  22. 22What is the gastric mill?Effectively sets of teeth which grind down food.
  23. 23What is the function of the pylorus?Oscillatory movement to churn up food.
  24. 24How does the Somatogastric Ganglion (STG) affect muscles?Motor neurons from STG synapse at different muscle types (eg constrictor muscles, pyloric dilator muscle) -- Recruitment of muscles.
  25. 25What are the two movements controlled by the STG? What does this mean in terms of the motoneurons which leave the STG?Gastric mill movement and Pyloric movement. Same neurons can participate in different movements.
  26. 26What are the three different type of neuromodulators?1) Descending input from higher control centres.
    2) Ascending input from sensory neurons.
    3) Hormonal release by neurosecretory structures.
  27. 27Within a single neuron where can neuromodulators act?On several different voltage-gated channels.
  28. 28Where can neuromodulators act? (general)Neurons or synaptic inputs.
  29. 29Where can neuromodulators converge?Onto the same voltage-dependent conductance.
  30. 30What range of effects can a single neuromodulator have?Can influence CPG in opposing directions.
  31. 31Name four different intrinsic membrane properties.1) Endogenous bursting
    2) Rebound firing
    3) Spike adaptation
    4) Plateau potentials
  32. 32Explain how plateau potentials occur?Activation of L-type calcium channels by 5-HT or NA leads to long lasting depolarisation (due to slow inward current)
  33. 33What determines intrinsic membrane properties? What in turn to different intrinsic membrane properties lead to?Combination of ion channels - eg 5-HT, DA and GABAb. Leads to different spiking properties.
  34. 34What determines endogenous bursting?Opening and closing on NMDA channels.
  35. 35Why are CPGs rhythmic?1) Pacemaker Neurons
    2) Emergent property of network
  36. 36How does a pacemaker neuron work? What does it produce? Where would you expect to find this system?Pacemaker neuron activates and deactivates surrounding neurons producing a continuous rhythmic output. Pacemaker neuron systems are found in the pyloric rhythm of the somatogastric ganglion and respiratory movements.
  37. 37When is and emergent property of network generation of CPGs seen? How does it work?In an initiated movement - eg. walking.
    No single neuron is a pacemaker but a neuron starts of activity in response to a sensory or CNS input. All neurons in network are connected and switch each other on and off.
  38. 38Where are the two different types of CPG generation found in the somatogastric ganglion? Which neuron is the pacemaker?Emergent network in the gastric system.
    Pacemaker in the pyloric system - lateral pyloric neuron (oscillatory discharge pattern observed).
  39. 39How do the movements produced by neuromodulators vary?Family of movements produced.
  40. 40Which neurotransmitter especially affects individual neurons as well as synapses between neurons?DA
  41. 41How do neuromodulators reconfigure networks? What is the consequence of this?Sum of effects on different sets/parts of neurons by neuromodulators lead to an overall and synchronised change in the neuronal network - leads to learned behaviours.
  42. 42How do neuromodulators lead to different movements?Different neuromodulators cause different firing patterns and therefore different types of movement.
  43. 43What is a polymorphic network? Where might you see an example of this?A single neuronal network which can produce several different physical actions based on the organism's needs.
    Tritonia diomedea (Sea slug)
  44. 44What are the two different types of movements produced by the single network in the Tritonia Diomedea?1) Rhythmic muscle-based escape swimming
    2) Non-rhythmic, cilia mediated crawling
  45. 45What causes reflexive withdrawal in the Tritonia Diomedea?Weak sensory input into the swimming CPG.
  46. 46What causes a swimming behaviour in the Tritonia Diomedea?Strong sensory input into the swimming CPG
  47. 47What causes the Tritonia Diomedea to switch into swim mode? What is the benefit of this?Serotonin release from dorsal swim interneurons. Allows the Tritonia Diomedea to rapidly switch into swim mode.
  48. 48What prevents the swim pattern in Tritonia Diomedea?Serotonin antagonists - inhibit excitatory interneurons.
  49. 49What are the two types of neural rhythmicity?1) Interactions among neurons (network based rhythmicity)
    2) Endogenous oscillator neurons - interactions among currents of individual neurons.
  50. 50What is a half centre oscillator?Two neurons which individually have no rhythmic capability but when reciprocally coupled produce a rhythmic output.
  51. 51How do Half centre oscillators fire? (2)1) Antiphase
    2) Relative phase or even synchrony
  52. 52What type of modes can half centre oscillators have? What are the intrinsic membrane properties of these?Release mode (Spike frequency adaptation)
    Escape mode (Rebound firing)
  53. 53How can Half Centre Oscillators be altered?By intrinsic and network properties.
  54. 54How do reciprocally coupled neurons produce a rhythmic pattern?Activation of one neuron causes inhibition of the other.
  55. 55How do neurons in Half Centre Oscillators switch between active and inactive states?Depends on intrinsic membrane patterns - eg. spike adaptation gradually causes the neuron to stop firing, disinhibiting the reciprocally coupled neuron causing it to fire.
  56. 56Why is a Lamprey used to model vertebrate CPGs? (5)1) Nervous system has a vertebrate organisation
    2) Shares many positive characteristics with invertebrates
    3) Spinal cord can survive days in vitro
    4) Has very few neurons
    5) Easily stimulated to produce fictive motor pattern.
  57. 57What was suggested by Ayers in 1983?Basal CPG is responsible for most undulating movements in a Lamprey - swimming forward & backward, burrowing in mud and crawling on solid surfaces.
    Sensory input affects intrinsic membrane properties > spike firing > movement type.
  58. 58What was seen in recordings taken from an intact lamprey swimming and an isolated lamprey spinal cord?Emg from muscles very similar to ventral root activity in isolated spinal cord.
  59. 59What is being developed from lamprey studies?Artificial CPGs being generated to simulate swimming movements in lamprey-like robots.
  60. 60What can simple mathematical vertebrate models be used to describe? (2)1) Basic principles proposed by T.G. Brown with integrate-to-threshold units organised with mutually inhibitory connections.
    2) Complex properties of behaviour and MLR-induced fictive movements.
  61. 61Over what time scales are human locomotive CPGs adaptable? What type of adaptation can be seen? How can different motor patterns adapt?1) Short and Long
    2) Gait patterns and different walking contexts
    3) independently
  62. 62How are the different directions of walking controlled?Independent networks for forwards and backwards walking.
  63. 63What are the three different types of spinal cord repair?1) Protecting nerve cells from further damage
    2) Replacing damaged nerve cells
    3) Stimulating the re-growth of axons and targeting their connections
  64. 64What is the new CPG based way of restoring function after spinal cord damage? What is its other benefit?Retrain CPG circuits using robotic gait system to guide patients legs. Also helps to prevent muscle waste.
  65. 65What does the firing pattern of a single neuron depend on?Intrinsic properties (eg ion channel composition) and network which neuron is a part of
  66. 66What does the activity of large neuronal ensembles reflect?Individual neuronal properties and patterns of connectivity.

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Degree Neurophysiology Fichas sobre Motor Lectures - Central Pattern Generators, creado por Anna mph el 28/12/2015.
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