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Organ Systems III > Motor Systems > Flashcards

Motor Systems Flashcards

0
Q

(CNS/spinal cord) generates motor programs.

A

CNS

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1
Q

What 3 things are involved in complex movement?

A

Integration of somatic, visual, and proprioceptive input; motor programs generated at various levels of the CNS; parallel and hierarchically arranged motor control systems from cerebral cortex down to the spinal cord.

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2
Q

(CNS/spinal cord) has more executive control of motor neurons.

A

Spinal cord

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3
Q

What type of neurons make up the lower motor neurons?

A

Alpha motor neurons

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4
Q

Where are the alpha motor neurons of the lower motor neurons?

A

Brain stem (cranial nerves) and ventral horn of the spinal cord

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5
Q

All movements generated by selective groups of _________

A

1 million lower motor neurons

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6
Q

What is the final common pathway for motor commands?

A

Lower motor neurons

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7
Q

What is muscle length regulated by?

A

Muscle spindle reflexes

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8
Q

What are intrafusal muscle fibers, parallel to extrafusal, surrounded by CT?

A

Muscle spindles

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9
Q

What do muscle spindles do?

A

Convey changes in muscle length to the spinal cord.

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10
Q

What 2 afferents detect changes in the length and velocity of muscles?

A

Ia (primary) and II (secondary) afferents

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11
Q

What interconnects physically gated ion channels in the axon of Ia and II neurons?

A

Cytoskeletal strands of spectrin

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12
Q

What distorts the axonal membrane, opening the Na/Cl channels?

A

Stretching the spindle

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13
Q

Na/Cl entry generates what?

A

A depolarizing generator potential, which in turn initiates APs in the axon

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14
Q

Which reflex is described by increased muscle length triggers homeostatic, negative feedback to maintain the limb in a constant position?

A

Stretch (myotatic) reflex

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15
Q

What is the pathway of the myotatic reflex?

A

Stretch spindle to Ia and II afferents to alpha motor neuron to contract same and synergistic muscles

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16
Q

Spindle afferents stimulate inhibitory interneurons to relax antagonist muscles.

A

Reciprocal innervation

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17
Q

What does the knee jerk test?

A

The integrity of the the stretch reflex circuit

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18
Q

What structure regulates spindle sensitivity during movement?

A

Gamma motor neurons

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19
Q

What do gamma motor neurons innervate?

A

Muscle ends of spindles

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20
Q

What is the result of tautening the spindle by the gamma neuron?

A

Increased sensitivity of Ia and II afferent neurons to muscle stretch.

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21
Q

(Whole muscle contraction/ gamma motor neuron activity) spindles are passively contracted and less sensitive to stretch and Ia afferent activity is decreased?

A

Whole muscle contraction.

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22
Q

(Whole muscle contraction/ gamma motor neuron activity) spindles are tonically contracted and mor sensitive to stretch. This sensitivity to stretch is maintained throughout the range of motion.

A

Gamma motor neuron activity

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23
Q

What are gamma motor neurons controlled by?

A

Brain/ brain stem. Not muscle/ receptors

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24
Q

Are gamma motor neurons controlled by muscle/ receptors?

A

No

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25
Q

As speed and difficulty of a movement increases, sensitivity of the spindles …

A

Increases

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26
Q

What is muscle tone regulated by?

A

Golgi tendon organs

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27
Q

Where are the Golgi tendon organs located?

A

In the muscle tendons

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28
Q

Are Golgi tendon organs innervated by gamma motor neurons?

A

No

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29
Q

Which reflex regulates the level of muscle tension?

A

Inverse myotatic reflex

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30
Q

How does the inverse myotatic reflex regulate the level of muscle tension?

A

Ib afferents innervate inter neurons that inhibit alpha motor neurons to the same muscle

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31
Q

Ib afferents stimulate excitatory interneurons to contract antagonist muscle.

A

Reciprocal innervation

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32
Q

What is the role of propriospinal neurons?

A

Integrate motor responses

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33
Q

Propriospinal neurons interconnect spinal levels for …. reflexes

A

Complex

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34
Q

Where are propriospinal neurons located?

A

Intermediate spinal grey matter

35
Q

Where are the propriospinal axons located?

A

Peripheral border of the ventral horn.

36
Q

What are axons that extend over the whole spinal cord that regulate proximal/axial muscles and full body posture?

A

Medial propriospinal neurons

37
Q

What structure extends fewer spinal segments and regulate distal muscles for independent control of fine movements?

A

Lateral propriospinal neurons

38
Q

What is the pathway o the flexor withdrawal and cross extension reflexes?

A

Pain to interneurons and propriospinal neurons to gamma motor neurons to muscles that withdraw ipsilateral limb and extend contralateral limb

39
Q

What are the two types of flexor withdrawal and cross extension reflexes?

A

Superficial and deep tendon

40
Q

(Superficial/deep) cutaneous pain induced limb withdrawal reflexes that use complex excitatory, inhibitory, and propriospinal pathway

A

Superficial reflexes

41
Q

(Superficial/deep) stretch and tension induced reflexes use simpler Ia, II, Ib afferent pathways to elicit or inhibit muscle contraction

A

Deep tendon reflexes

42
Q

Where are the 3 structures that support upper motor neurons?

A

Cerebral cortex, reticular formation, and vestibular nuclei

43
Q

Where do the upper motor neurons project?

A

Down to the lower motor neurons in the spinal cord an cranial nerve nuclei

44
Q

Brain stem pathways of upper motor neurons maintain what 2 things?

A

Posture and balance

45
Q

Motor cortex upper motor neurons regulate what?

A

Fine movement in extremities

46
Q

What are the 3 tracts that descend from the motor cortex?

A

Corticospinal tract, corticonuclear tract, and the corticoreticular tract

47
Q

What are the 4 motor related tracts in the white matter?

A

Lateral corticospinal tract, ventral corticospinal tract, vestibulospinal tract, and reticulospinal tract

48
Q

What are the 2 segments of the reticulospinal tract?

A

Medial and lateral

49
Q

Where does the corticospinal tract project to?

A

The alpha and gamma motor neurons in the ventral horn of the spinal cord

50
Q

What is the pathway of the corticospinal tract?

A

Internal capsule, to the cerebral puduncles in the midbrain, to the pyramids in the medulla, then 90/10 decussation of lateral and ventral corticospinal tracts

51
Q

Bundle of axons in the cerebral hemisphere?

A

Internal capsule

52
Q

Where is a common site of strokes?

A

Internal capsule

53
Q

Which tract controls muscles of face, head, and neck?

A

Corticonuclear tract

54
Q

Where does the corticonuclear tract project to?

A

Motor neurons of the cranial nerves

55
Q

Which tract is the route for primary motor and premotor cortices that project to the pontine and medullary reticular formation?

A

Corticoreticular tract

56
Q

Which tract smoothes out general movements?

A

Corticoreticular tract

57
Q

How does the corticoreticular tract smooth out general movements?

A

By limiting inhibition among extensor muscles of the lower limb and breaks up stereotypic patterns generated in the reticular formation

58
Q

Where does the corticospinal tract dessucate?

A

Medulla

59
Q

What is the function of the lateral corticospinal tract?

A

Fine control of movements

60
Q

Which tract forms a large, homuncular areas for the face and hands?

A

Lateral corticospinal tract

61
Q

Where does the anterior corticospinal tract project?

A

Bilaterally in the spinal cord

62
Q

Which tract is made up of the 10% uncrossed axons of the corticospinal tract?

A

Ventral corticospinal tract

63
Q

Which tract is made up of the 90% crossed axons of the corticospinal tract?

A

Lateral corticospinal tract

64
Q

What is the ventral corticospinal tract responsible for?

A

Posture of the neck and trunk

65
Q

Which tract results from the vestibular nuclei in the medulla and relays head movement activity from the semi circular duct, utricle, a d saccule receptors to the spinal cord?

A

Vestibulospinal tract

66
Q

Where does the vestibulospinal tract relay head movement activity from?

A

Semi circular duct, utricle, and saccule receptors

67
Q

What does the vestibulospinal tract activate?

A

Extensors of the lower limb and flexors of the upper limb

68
Q

What is the primary responsibility of the vestibulospinal tract?

A

Maintain posture and balance

69
Q

What is the path of the reticulospinal tract?

A

Reticular formation neurons in the pons and medulla project down to the motor neurons of the trunk muscles and proximal muscles of the upper and lower limb

70
Q

Which tract facilitates voluntary movements and increases muscle tone via gamma motor neurons?

A

Medial reticulospinal tract

71
Q

Which tract is responsible for the anti-gravity posture?

A

Medial reticulospinal tract

72
Q

Extension of the lower limb and flexion of the upper limb

A

Anti gravity posture

73
Q

Which tract inhibits voluntary actions and reduces tone?

A

Lateral reticulospinal tract

74
Q

Which structures develop strategies for motor programs?

A

Association areas (supplemental, premotor)

75
Q

Where are the motor programs sent?

A

To the primary motor cortex

76
Q

Where is the primary motor complex?

A

Precentral gyrus

77
Q

What do the cortical columns in the precentral gyrus activate?

A

Small groups of muscles for fine movements

78
Q

Is the somatotopy fixed?

A

No– a cortical column can innervate different sets of motor neurons

79
Q

What is the function of the supplementary motor cortex?

A

Ensures correct motor sequence independent of external conditions

80
Q

Which cortex is activated during mental rehearsal?

A

Supplementary motor cortex

81
Q

What is the responsibility of the premotor cortex?

A

Integrate spatial and sensory information as well as abstract rules in the planning of movement

82
Q

What do premotor neurons encode?

A

Intention to perform a particular movement

83
Q

What is involved in the selection of movements based on external or internal events?

A

Premotor neurons

84
Q

What is the part of the pre motor cortex that controls motor preparation for speech?

A

Broca’s area

Organ Systems III (13 decks)

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