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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
Are gamma motor neurons controlled by muscle/ receptors?
No
25
As speed and difficulty of a movement increases, sensitivity of the spindles ...
Increases
26
What is muscle tone regulated by?
Golgi tendon organs
27
Where are the Golgi tendon organs located?
In the muscle tendons
28
Are Golgi tendon organs innervated by gamma motor neurons?
No
29
Which reflex regulates the level of muscle tension?
Inverse myotatic reflex
30
How does the inverse myotatic reflex regulate the level of muscle tension?
Ib afferents innervate inter neurons that inhibit alpha motor neurons to the same muscle
31
Ib afferents stimulate excitatory interneurons to contract antagonist muscle.
Reciprocal innervation
32
What is the role of propriospinal neurons?
Integrate motor responses
33
Propriospinal neurons interconnect spinal levels for .... reflexes
Complex
34
Where are propriospinal neurons located?
Intermediate spinal grey matter
35
Where are the propriospinal axons located?
Peripheral border of the ventral horn.
36
What are axons that extend over the whole spinal cord that regulate proximal/axial muscles and full body posture?
Medial propriospinal neurons
37
What structure extends fewer spinal segments and regulate distal muscles for independent control of fine movements?
Lateral propriospinal neurons
38
What is the pathway o the flexor withdrawal and cross extension reflexes?
Pain to interneurons and propriospinal neurons to gamma motor neurons to muscles that withdraw ipsilateral limb and extend contralateral limb
39
What are the two types of flexor withdrawal and cross extension reflexes?
Superficial and deep tendon
40
(Superficial/deep) cutaneous pain induced limb withdrawal reflexes that use complex excitatory, inhibitory, and propriospinal pathway
Superficial reflexes
41
(Superficial/deep) stretch and tension induced reflexes use simpler Ia, II, Ib afferent pathways to elicit or inhibit muscle contraction
Deep tendon reflexes
42
Where are the 3 structures that support upper motor neurons?
Cerebral cortex, reticular formation, and vestibular nuclei
43
Where do the upper motor neurons project?
Down to the lower motor neurons in the spinal cord an cranial nerve nuclei
44
Brain stem pathways of upper motor neurons maintain what 2 things?
Posture and balance
45
Motor cortex upper motor neurons regulate what?
Fine movement in extremities
46
What are the 3 tracts that descend from the motor cortex?
Corticospinal tract, corticonuclear tract, and the corticoreticular tract
47
What are the 4 motor related tracts in the white matter?
Lateral corticospinal tract, ventral corticospinal tract, vestibulospinal tract, and reticulospinal tract
48
What are the 2 segments of the reticulospinal tract?
Medial and lateral
49
Where does the corticospinal tract project to?
The alpha and gamma motor neurons in the ventral horn of the spinal cord
50
What is the pathway of the corticospinal tract?
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
Bundle of axons in the cerebral hemisphere?
Internal capsule
52
Where is a common site of strokes?
Internal capsule
53
Which tract controls muscles of face, head, and neck?
Corticonuclear tract
54
Where does the corticonuclear tract project to?
Motor neurons of the cranial nerves
55
Which tract is the route for primary motor and premotor cortices that project to the pontine and medullary reticular formation?
Corticoreticular tract
56
Which tract smoothes out general movements?
Corticoreticular tract
57
How does the corticoreticular tract smooth out general movements?
By limiting inhibition among extensor muscles of the lower limb and breaks up stereotypic patterns generated in the reticular formation
58
Where does the corticospinal tract dessucate?
Medulla
59
What is the function of the lateral corticospinal tract?
Fine control of movements
60
Which tract forms a large, homuncular areas for the face and hands?
Lateral corticospinal tract
61
Where does the anterior corticospinal tract project?
Bilaterally in the spinal cord
62
Which tract is made up of the 10% uncrossed axons of the corticospinal tract?
Ventral corticospinal tract
63
Which tract is made up of the 90% crossed axons of the corticospinal tract?
Lateral corticospinal tract
64
What is the ventral corticospinal tract responsible for?
Posture of the neck and trunk
65
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?
Vestibulospinal tract
66
Where does the vestibulospinal tract relay head movement activity from?
Semi circular duct, utricle, and saccule receptors
67
What does the vestibulospinal tract activate?
Extensors of the lower limb and flexors of the upper limb
68
What is the primary responsibility of the vestibulospinal tract?
Maintain posture and balance
69
What is the path of the reticulospinal tract?
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
Which tract facilitates voluntary movements and increases muscle tone via gamma motor neurons?
Medial reticulospinal tract
71
Which tract is responsible for the anti-gravity posture?
Medial reticulospinal tract
72
Extension of the lower limb and flexion of the upper limb
Anti gravity posture
73
Which tract inhibits voluntary actions and reduces tone?
Lateral reticulospinal tract
74
Which structures develop strategies for motor programs?
Association areas (supplemental, premotor)
75
Where are the motor programs sent?
To the primary motor cortex
76
Where is the primary motor complex?
Precentral gyrus
77
What do the cortical columns in the precentral gyrus activate?
Small groups of muscles for fine movements
78
Is the somatotopy fixed?
No-- a cortical column can innervate different sets of motor neurons
79
What is the function of the supplementary motor cortex?
Ensures correct motor sequence independent of external conditions
80
Which cortex is activated during mental rehearsal?
Supplementary motor cortex
81
What is the responsibility of the premotor cortex?
Integrate spatial and sensory information as well as abstract rules in the planning of movement
82
What do premotor neurons encode?
Intention to perform a particular movement
83
What is involved in the selection of movements based on external or internal events?
Premotor neurons
84
What is the part of the pre motor cortex that controls motor preparation for speech?
Broca's area

Organ Systems III (13 decks)

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