Brain and Behavior

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Brain and Behavior
2010-05-05 17:22:17
Lower Motor Neurons

Exam 3 Material
Show Answers:

  1. Genetically programmed movements that are initiated by receptor stimulation and result in stereotyped movement patterns.
  2. What are back-and-forth movements (like breathing or walking) that
    are run by preprogrammed cyclic motor circuits called central pattern generators or CPGs?
    oscillating movements
  3. elaborate genetically-programmed movement sequences that are
    largely species specific and are preprogrammed, but are considerably
    modified by experience.
    fixed pattern movements
  4. What are movements that are learned through trial-and-error repetition and are initiated by one’s decisions (in the lateral prefrontal cortex).
    Voluntary movements
  5. Upper motor neurons include:
    A)__ cortex for voluntary movements
    B)__ motor centers for posture and balance movements
    They include: a) motor cortex for voluntary movements (based on personal decision); b) brainstem motor centers for posture and balance movements.
    1)areas of the ___ cortex
    2)___ ___
    3) ____
    These areas are involved in ___ and ____ of motor sequences.
    areas of the frontal cortex, basal ganglia, and cerebellum; - are involved in planning, selection and coordination of motor sequences
  7. What are the two types of lower motor neurons and their targets?
    • 1) Alpha motor neurons: supply ordianry force generating muscle fibers (aka: extrafusal fibers)
    • 2) Gamma motor neurons: supply intrafusal fibers in stretch receptors.

    • Alpha- force- extra
    • Gamma- stretch- intra
  8. What consists of all motor neurons that supply a single muscle?
    motor neuron pool
  9. Neurons of the spinal motor control system are located mainly in the ____ ___. They include 1) and 2).
    • anterior horn
    • spinal motor networks and spinal lower motor neurons
  10. What are two ways that the spinal motor networks can be recruited?
    • Afferent fibers from periphery
    • and
    • Upper motor neurons
  11. After a transection of the spinal cord and a period of spinal shock, spinal reflexes can be initiated ____ the level of the lesion by receptor stimulation.
  12. Correction of balance need to be super fast which is why the afferent fibers of the stretch receptors synapse immediately in the ___ horn of the spinal cord.
  13. Stretch receptor cells are located in the ___ ____.
    muscle spindle
  14. Within the muscle spindle, specialized receptors called ____ fibers are joined by connective tissue to neighboring force generating ____ fibers that shorten the whole muscle.
    • intrafusal
    • extrafusal
  15. ____ receptors have ion channels that open in response to deformation of the cell membrane.
    stretch/ mechano
  16. Each stretch receptor cell (aka IFF) contains:
    ___ in the central part of the cell
    ___ in the distal part of the cell
    • stretch receptors in the central part of the cell
    • contractile fibers in the distal part of the cell
  17. The intrafusal fibers in a stretch receptor cell change the length of the distal ends of the cell during ____ in parallel with changes in the length of neighboring EFFs that have been ordered by higher motor centers. This simultaneous relaxation or contraction of intrafusal fibers prevents the central, receptor part of stretch receptor cell from detecting/ correcting ___ movements.
    • desirable movements
    • desirable
  18. True or False
    Upper motor neurons send orders to alpha motor neurons only.
    • False.
    • Both gamma and alpha
  19. The simultaneous and proportional contraction/ relaxation of EFFs and IFFs of a muscle is called :
    Gamma coactivation
  20. Clinically, dynamic stretch receptors are important in evaluating ___ ___ while static stretch receptors are important for evaluating __ __.
    • stretch reflex
    • muscle tone
  21. The ___ ___ is used by brainstem tonically-active cells to establish and maintain a baseline or resting muscle tone.
    Gamma loop
  22. Group II Stretch Afferents
  23. Clinically, on stroking the upper medial thigh, the _ipsi or contra?___ cremaster muscle contracts to “elevate
    the testis” away from the stimulus. This reflex involves: cutaneous receptors of and afferent fibers
    from the __ dermatome (ilioinguinal nerve); synapses at the L 1-2 levels of the spinal cord; motor
    fibers to the cremaster muscle (L1-2, genitofemoral nerve). This is a clinical test for function of
    peripheral and CNS levels __ and ___.
    • Ipsilateral
    • L1
    • L1 and L2
  24. Stroking the upper abdominals tests for reflexes at what levels?
    T8- T10
  25. Stroking the lower muscles of the abdominal area tests for the reflexes at what level?
  26. Spinal central pattern generators (CPGs) are hardwired circuits for what type of movement??
    rhythmic/ oscillating movements like breathing or walking
  27. CPG triggers include fibers from ___ __ and ____ motor centers.
    peripheral receptors and brainstem motor centers.
  28. Spinal CPGs include:
    _____ (upper cervical cord)
    _____(cervical cord)
    _____(lumbar spinal cord)
    • breathing
    • arm locomotion during walking
    • leg locomotion
  29. Triggers for breathing movements include: ___ receptors in breathing muscles; ____ respiratory centers that integrate input from blood gases. The ___ cortex serves as a controller to voluntarily control respiratory rate and coordinate breathing with speech.
    • stretch
    • brainstem
    • motor
  30. Triggers for walking (locomotor CPGs) include:____receptors in the plantar (lower) surface of the foot; input from higher “locomotion centers.” The ____ cortex serves as a controller.
    • touch
    • motor
  31. All brainstem motor nuclei are located in the base. T or F
    False- located in the Tegmentum
  32. The GSE and GVE motor nuclei will be located in the ____ area in the tegmentum of the brainstem.
    periventricular area
  33. Most BE motor nuclei in the brainstem are located in the reticular formation. T or F?
  34. All brainstem levels contain GSE and BE motor nuclei. T or F
  35. The midbrain contains the __ motor nuclei for eyeball and eyelid movement.
    GSE of oculomotor and trochlear
  36. The caudal pons contains ___ motor nuclei for eyeball muscles and ___ motor nuclei for facial muscles.

    The rostral pons contains ___ motor nuclei for jaw muscles.
    • GSE
    • BE
    • BE
  37. The GSE motor nuclei of the medulla control the muscles of the ____ while the BE nuclei control the muscles of the ____.
    • tongue
    • pharynx/larynx
  38. The oculomotor nucleus (GSE, CN 3) is located in the ____ _____ in the ventral periaqueductal gray. The nerve roots exit medially.
    rostral midbrain
  39. When there is a lesion of the oculomotor nerve in rostral midbrain what deficits would be observed?
    lesion -> severe ptosis (eyelid droop); upward gaze deficiency; at rest, eyeball is down & out

    • Bc oculomotor nerve innervates
    • levator palpebrae m.; all extraocular mm. except sup. oblique & lateral rectus
    • - Note: this nucleus is near the Edinger Westphal nuc. of III (GVE to intrinsic mm. of eyeball)
  40. A vascular lesion of the posterior cerebral artery in the rostral midbrain would affect what cranial nerve?
  41. The trochlear nucleus (CN 6) is located where in the brainstem?
    the caudal midbrain in the ventral periaqueductal gray
  42. Trochlear Nucleus GSE innervates the _____ ____ ____muscle and cross the midline to exit ____.
    • contralateral superior obliques
    • dorsally
  43. A lesion of the trochlear nucleus or fibers results in:
    weakness of downward gaze
  44. A vascular lesion of the posterior cerebral or superior cerebellar artery in the caudal midbrain will result in a deficit to what nerve? What will be the clinical deficit
    • Trochlear
    • Difficulty in downward gaze
  45. The trigeminal motor nucleus is located where? What is the blood supply to this region? A lesion of the this area will result in what clinical deficits?
    • The mid pons in the dorsoloteral reticular formation.
    • Long circumferential basilar and superior cerebellar arteries.
    • weakness during chewing and loss of jaw jerk reflex
  46. The abducens nucleus is located where? What is the blood supply? What clinical deficit would occur when this area is lesioned?
    • The caudal pons
    • Basilar
    • Patient would be unable to move eyeballs laterally
  47. The facial motor nucleus is located where? The blood supply to this region is the? Clinical deficits will be?
    • the caudal pons
    • AICA
    • Problems with facial expression, closing eyelids, and speech.
  48. Failure to close one's eyelids upon touching the cornea (the corneal reflex) indicates a lesion of either the ___ nerve which is the afferent nerve or the ____ which is the motor nerve.
    • trigeminal
    • facial
  49. The hypoglossal nucleus is located where? What is the blood supply? The clinical deficits from a lesion in this region would be???
    • mid/rostral medulla
    • Anterior spinal artery
    • tongue weakness so difficulty with chewing, swallowing, and speech.
  50. The nucleus ambiguous is located where? What is the blood supply to this area? What are the clinical deficits associated with a lesion of this nucleus?
    • mid/ rostral medulla in the ventral reticular formation
    • PICA
    • drooping of palatal arch
    • deviation of uvulva opposite to side of the lesion
    • hoarse voice due to paralysis of laryngeal muscles
    • problems with sound/speech production, swallowing, and breathing
  51. The Accessory nucleus is located where? What is the blood supply? What are the clinical deficits?
    • c1-c5 of spinal cord
    • anterior spinal artery
    • difficulty with head position and head turning
    • shoulder droop
    • difficulty tilting chin to opposite side
  52. What is the main reflex used to evaluate midbrain function in comatose patients?
    pupillary light reflex
  53. What nuclei are important for the pupillary light reflex?
    Edinger-Westphal and Oculomotor
  54. The afferent limb of the pupillary light reflex is cranial nerve __ while the efferent limb in cranial nerve __.
    2 and 3
  55. The corneal reflex elicits a bilateral response by stimulating both ____ nuclei. This can evaluate the function at the level of the _____ in the brainstem. What nucleus is important in this reflex?
    • facial
    • pons
    • facial nucleus
  56. The jaw jerk reflex bilaterally stimulates the efferent fibers of cranial nerve __. This tests functioning at the level of the ____ in the brainstem. What nucleus is important in this reflex?
    • 5
    • midpons
    • mesenphalic nucleus of 5
  57. The gag reflex bilaterally stimulates the efferent limbs of cranial nerves ___ and ___. This tests for function at the level of the ___ in the brainstem. What nucleus is important in this reflex?
    • 9 and 10
    • medulla
    • nucleus ambiguous
  58. The vestibulo-Ocular reflex is a bilateral excitement of what nerves/ nuclei?
    • 3,4,6
    • All extraocular muscles
  59. The pontine breathing center coordinates the movement of the cranial and thoracic muscles bysending signals to the medullary and spinal __ ___ __.
    central pattern generators