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Flashcards

NAB motor

Daniel Beresford Inglês 72 flashcards

Flashcards do conjunto (72)

  1. 1RedundancyGoals can be achieved in different ways
  2. 2Efference copyMotor commands relayed back to the CNS which can be used to simulate the future response of the motor system and thus predict the movement that will follow. Part of a 'forward model'.
  3. 3Sommatotropic organisationDistal muscles represented laterally
  4. 4Motor unitsSlow, fast (fatigue resistant), fast fatigable
  5. 5Rate codingMotoneuron firing rate translates into force generated. Twitches generated by mm. fuse into a tetanus at quite low frequencies.
  6. 6Motoneuron recruitmentControlling which motor units are active. As more force is needed, more motoneurons are recruited.
  7. 7Size principle of motoneuron recruitmentAs force increases, the lowest force motor units are recruited first- the highest last. Therefore as smooth as possible.
  8. 8Developmental plasticityMotoneurons with low firing threshold innervate few muscle fibres and induce them to become slow twitch, low force and fatique resistant. Motoneurons with the highest firing thresholds (recruited last) innervate many muscle fibres and induce them to become fast twitch and high force, but fatigable
  9. 9Local signDifferent reflexes are evoked from different locations.
  10. 10Muscle spindle afferentsMuscle stretch receptors
  11. 11Golgi tendon organ afferentsMuscle tension receptors. Signal 'active tension' as passive tension is absorbed by elasticity of muscle fibres.
  12. 12Joint receptorsSignal joint position and movement, especially at the extremes.
  13. 13Intrafusal fibresFibres of muscle spindle
  14. 14Bag fibresHave a swollen (elastic, non-contractile) central region containing many nuclei (the bag) and contractile ends which are viscoelastic.
  15. 15Chain fibresAre of uniform diameter and are uniformly contractile along their length. Sensory endings on them (especially II endings) signal muscle length approx. linearly (a static response).
  16. 16Primary of 1a spindle afferentsLarge (fast conducting) axons which have terminal branches that end in coils (annulospiral endings) around the central region of the intrafusal muscle fibres.
  17. 17Secondary or II spindle afferentsSmaller, slower conducting afferent fibres end adjacent to the central region of the intrafusal muscle fibres.
  18. 18y-motoneuronsA specialised group of smaller, slower-conducting motoneurons innervate the intrafusal fibres away from the sensory endings.
  19. 19Bag fibre signallingRapid stretches applied to bag fibres immediately elongate the central bag region (dynamic response), which is subsequently relieved as the viscous ends of the fibres elongate reducing stretch of the central region. As a result, during the stretch the central region is greatly elongated, generating a strong initial response but this declines to be distributed across the whole fibre at the end of the stretch.
    These properties give the primary endings on the bad fibres a largely rapidly adapting response. Their responses signal changes in muscle length.
  20. 20Efference copy regarding muscle spindlesTo interpret the muscle spindle signals unambiguously in terms of muscle length or length change the brain needs to ‘know’ the y motoneuron activity.
  21. 21Monosynaptic connectionsMuscle spindle afferents to the a-motoneurons that innervate the same muscle underly the stretch reflex
  22. 22Eye and tongue musclesExceptions as don't have a stretch reflex
  23. 23Reciprocal inhibitionExcitation of glycinergic interneurons (Ia inhibitory interneurons) that inhibit antagonist muscles, preventing further stretch. -> limb joints
  24. 24MyoclonusOscillation following muscle stretch.
  25. 25KinesthesiaSense of position, movement and effort
  26. 26Recurrent inhibitionGenerated by Renshaw cells. Motoneuron axons have recurrent collaterals within the spinal cord that innervate RC's. Regulate timing of MN firing, preventing synchrony.
  27. 27Babinskis signResponse to scratching the sole of the foot. Infant toes curl upward/adult downward. Following brain dmg, sign can reappear.
  28. 28SpasticityExaggerated stretch reflexes.
  29. 29Ventromedial pathwaysAxial (trunk) and proximal limb muscles and play a role in whole body movement (locomotion/posture).
  30. 30VestibulospinalFrom vestibular system
  31. 31ReticulospinalFrom reticular formation
  32. 32TectospinalFrom superior colliculus
  33. 33Dorsolateral systemsMost important route through which goal directed movements of the limbs are driven, especially movements of the hands, feet and face (and other prehensile structures, like the lips). Different species have different organisations.
  34. 34RubrospinalArises from the red nucleus in the midbrain, and is important in most species of mammal, e.g. cats and dogs, including monkeys. It is probably vestigial in man.
  35. 35Corticospinal tractArising from motor areas of cerebral cortex is the largest descending pathway in all mammals, and is the dominant descending control pathway in man.
  36. 36CupulaMass that almost closes semicircular canal- contains hair cells. Neutrally buoyant in endolymph. Deflected when head moves as fluid stays still due to inertia.
  37. 37Gaze-fixing mechanismsKeeps eyes fixed relative to the outside world.
  38. 38Vestibulo-ocular reflexMoves eyes equal and opposite to head. FF control system. SS canals > Vestibular nuclei > MLF > OM nuclei > eye muscles. Calibration requires the cerebellum.
  39. 39Vestibulocolic systemProduce compensatory head movements, as in owls
  40. 40Optokinetic systemMoves the eyes to follow slow movements of the visual field, this happens when looking out of a train or bus window. Optokinetic movements require detection of slow movements of the visual image. They are driven via the visual cortex.
  41. 41NystagmusSaw-tooth eye movements- resetting the eye to the centre. Physiologically nystagmus can occur in response to optokinetic or vestibular stimuli. Pathologically, nystagmus follows cerebellar or vestibular damage
  42. 42Gaze-shifting mechanismsMoving the eye as quickly as possible and resting at a new position. Saccades.
  43. 43SaccadesRetina > SC > brainsten reticular formation > OM nuclei. Deep layers of the SC also project to the cervical spinal cord (tectospinal tract), so neck movements can accompany eye movements.
  44. 44Smooth pursuitSlower eye movements made to 'follow' moving objects. FF predictive movements. Involves regions of the cortex, brainstem regions and cerebellum.
  45. 45Corticospinal tractCrossed pathway (cross in the lower medulla). Primary motor cortex > Internal capsule (FB) > Cerebral peduncle (MB) > pyramid (medulla) > lateral corticospinal tract in the dorsolateral funiculus of the spinal cord. Terminates in the intermediate zone in cats and dogs. 10-20% of fibres don't cross and travel ipsilaterally > uncrossed ventral tract > axial muscles.
  46. 46Corticobulbar fibresControl cranial nerve function
  47. 47Regulation of grip forceRegulated by motor cortex. Feedback control system.
  48. 48Supplementary motor areaInternally generated and bimanual movements. Heaviest projections from the basal ganglia.
  49. 49Lateral premotor areaMovements dependent on a sensory trigger signal. Heaviest projections from the cerebellum.
  50. 50Mirror neuronsNeurons that fire in relation to making a movement, but also to seeing another person making the same movement
  51. 51HypotoniaWeakness
  52. 52DysmetriaInappropriate displacement e.g. overreaching
  53. 53DysdiadochokinesisInability to make rapid alternating movement
  54. 54Decomposition of movementLack of coordination of different joint movements
  55. 55Cerebellar cortexOutput exclusively from purkinje cells (inhibit (GABA) cells in the deep cerebellar nuclei > motor structures). 3 layers.
  56. 56Dentate nucleusLargest cerebellar nuclei in man. Projects to parts of the thalamus (VL & VA) the supply motor and motor association areas of the cerebral cortex.
  57. 57Granule cellsOnly excitatory neurons, axons form parallel fibres that excite Purkinje cells.
  58. 58Mossy fibresExcite granule cells. Arise from many brain structures, some from sensory pathways, in man particularly the pons (cerebro-cerebellar relay).
  59. 59Climbing fibresArise only from the inferior olive in the medulla. Each purkinje cell receives input from 1 climbing fibre (massive connection, always causes AP in Pj cell).
  60. 60Long-term depressionTrained Pj cell after mossy and climbing fibres fire together.
  61. 61FlocculusInvolved in learning the VOR.
  62. 62Basal ganglia functionConcerned with motor learning, but not in specifying detailed parameters of movement (cerebellum). They are also involved in other types of learning, selection of movement patterns and triggering of movements. Action selection.
  63. 63Basal ganglia definitionA collection of large subcortical forebrain nuclei. The main nuclei are the Putamen & Caudate and the globus pallidus. Because of the appearance of these nuclei (with stripes of fibres crossing grey matter) they are alternatively referred to as the striatum. 2 midbrain nuclei, (substantia nigra & subthalamic nucleus are functionally connected with these nuclei as a functional unit. The nuclei in the basal ganglia are mainly interconnected by sequential inhibitory connections (GABA). The ultimate output is inhibitory to the thalamus.
  64. 64ChoreaUnexpected dancing movement
  65. 65AthetosisWrithing movement of hand or face
  66. 66BallismusFlailing ballistic movements
  67. 67Internal globus pallidusBasal ganglia output neurons
  68. 68Direct circuitCorticostriate fibres > + caudate/putamen > - internal globus pallidus > - thalamus. Activity of this pathway permits movement.
  69. 69Indirect circuitCorticostriate fibres > + caudate/putamen neurons > - ext. GP > - subthalamic nucleus > + int.GP meaning increased activity so increasing inhibition of thalamus and thus prevents movement.
  70. 70DopamineSubstantia nigra. Activates the pathway to the int. gp by D1Rs and suppresses the pathway to the ext. gp by D2Rs. Loss of D2 therefore results in increased inhibition of the thalamus.
    Also involved in habit learning as the release of dopamine reinforces the synapses that were active to generate the successful output, so that when those synapses are activated again the output is generated again.
  71. 71Neurosurgical treatmentsControlled lesions of the Globus Pallidus (pallidotomy) or, more common nowadays, deep brain stimulation in the subthalamic nucleus. These disrupt the excessive inhibition of the thalamic neurons, alleviating the symptoms.
  72. 72—

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FlashCards sobre NAB motor, criado por Daniel Beresford em 18-05-2018.
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