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Neuroscience > Descending Tracts > Flashcards

Descending Tracts Flashcards

1
Q

What area does the ventral medial descending system primarily receive fibers from?

A
  • Cortical area 6
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2
Q

Where is the ventral medial descending system located in the spinal cord (when viewed in A-P cross-section)?

A
  • Ventro-medial portion of intermediate gray matter
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3
Q

What funiculi are the tracts of the ventral medial descending system located within?

A
  • Ventral, and ventral lateral funiculi
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4
Q

What type of interneurons do the tracts of the ventral medial descending system synapse on?

A
  • Long propriospinal interneurons
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5
Q

If one side of the ventral medial descending system is damaged, is the system comprised unilaterally? Why or why not?

A
  • The ventral medial descending system is bilaterally distributed meaning left and right both contribute control to theleft and right
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6
Q

Why does the ventral medial descending system have many synapses?

A
  • It has a high degree of collateralization
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7
Q

What is the effect on the musculature of the ventral medial descending system due to dense collateralization?

A
  • Large groups of muscles are activated together
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8
Q

What is the function of the muscle groups innervated by the ventral medial descending system?

A
  • Postural, and stabilization by synergistic action of axial and proximal muscles
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9
Q

What 5 tracts make up the ventral medial descending system?

A
  • Lateral vestibulospinal
  • Medial vestibulospinal
  • Lateral reticulospinal (medullary)
  • Medial reticulospinal (pontine)
  • Tectospinal
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10
Q

Where in the spinal cord are long and short proprioceptive interneurons located? (viewed in A-P cross-section)

A
  • Long is medially located

- Short is laterally located

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11
Q

What are the alternate names of the medial and lateral reticulospinal tracts?

A
  • Lateral reticulospinal –> Medullary

- Medial reticulospinal –> Pontine

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12
Q

Which reticulospinal tract is tonically active?

A
  • Medial/ Pontine
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13
Q

What muscle groups are activated and inhibited by the medial/ pontine reticulospinal tract? What is the function of this?

A
  • Extensors activated
  • Flexors inhibited
  • Drive upright posture
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14
Q

How does the medial/ pontine reticulospinal tract travel through the spinal cord?

A
  • Travels down ventral medial funiculus

- Enter gray matter, and synapse on alpha motor neurons

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15
Q

What muscle groups are activated and inhibited by the lateral/ medullary reticulospinal tract?

A
  • Flexors activated

- Extensors inhibited

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16
Q

Which reticulospinal tract is more dominant?

A
  • Medial
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17
Q

What structure are the vestibular nuclei located within, and what system are they connected to?

A
  • Nuclei found within medulla

- Connected to vestibular system within inner ear

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18
Q

Which vestibular tract is not billateral?

A

The lateral

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19
Q

Which vestibular tract only has phasic properties?

A
  • The lateral
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20
Q

Which vestibulospinal tract is monosynaptic?

A

The lateral

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21
Q

Is the lateral vestibulospinal tract ipsilateral or contralateral?

A

Ipsilateral

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22
Q

What is the origin of the tectospinal tract?

A

The tectum on the midbrain

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23
Q

What are the 2 lateral descending tracts?

A
  • Rubrospinal

- Ponto spinal

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24
Q

Which of the 2 lateral descending systems originate from the reticular formation?

A
  • Pontospinal
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25
Q

Where is area 6?

A
  • Anterior to the central sulcus
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26
Q

Where is area 4?

A
  • The precentral gyrus
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27
Q

From what area in the cortex do the fibers of the lateral descending system originate from?

A

Area 4

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28
Q

What type of representation does the lateral descending system display? (Which side of the body does the position of the origination of the tract correspond with?)

A

Contralateral representation

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29
Q

Where is the lateral system found in the gray matter of the cerebrum?

A
  • Lateral and dorsal portions of intermediate gray
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30
Q

Where is the lateral descending system found the medulla?

A
  • Dorsal-laterally
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31
Q

Where is the lateral descending system found in the spinal cord?

A

The lateral funiculus

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32
Q

What types of neurons are found in the intermediate gray?

A

Short propriospinal interneurons

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33
Q

Where does the rubrospinal tract originate from?

A

The red nucleus

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34
Q

Does the rubrospinal tract innervate proximal or distal musculature?

A

Distal

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35
Q

Does the rubrospinal tract provide discrete or gross control?

A

Discrete

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36
Q

What is the major function of the rubrospinal tract?

A

Fractionalizes movement, especially of distal musculature

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37
Q

What will a lesion of the rubrospinal tract cause?

A
  • Decreased dexterity of fingers and distal musculature
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38
Q

Does the rubrospinal tract drive flexors or extensors?

A

Flexors

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39
Q

From where does the pyramidal system originate?

A
  • Directly from cerebral cortex
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40
Q

Where is the pyramidal system located in the spinal cord? (x-section)

A
  • Laterally
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41
Q

How much collateralization is found in the pyramidal system?

A

Very little

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42
Q

What systems does the pyramidal system feed into?

A
  • Ventral and lateral
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43
Q

What are the 2 main functions of the pyramidal tract?

A
  • Voluntary control

- Very highly fractionalized movement

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44
Q

What special types of movements are the pyramidal tracts involved in?

A
  • Movements that require learning and selection
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45
Q

What effect does the pyramidal system have on sensory input?

A

Modulation (especially at the dorsal horn)

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46
Q

What representation does the pyramidal system have?

A

Contrallateral

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47
Q

What percent of the pyramidal system goes to the lateral cell column? The medial?

A

85 % lateral

15 % medial

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48
Q

Which system is most responsible for pathology in humans?

A

The pyramidal system

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49
Q

What are the 3 tracts of the pyramidal system?

A
  • Lateral corticospinal
  • Anterior corticospinal
  • Tract of barnes
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50
Q

What is another name for the pyramidal system?

A

Volitional

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51
Q

What are some results of a lesion to the pyramidal system?

A
  • LMNS
  • Decreased muscle tone
  • Decreased cutaneous reflexes
  • Slow tendon reflexes
  • Decreased initiation and execution of movement (especially digits)
  • Weakness
  • Fatigability
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52
Q

Where do the tracts of the pyramidal system split?

A

In the spinal cord

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53
Q

What is the tract of barnes?

A

The ~ 2 % of the pyramidal system that stays ipsilateral through the spinal cord

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54
Q

Where are the descending autonomic pathways located?

A
  • Ventral and lateral funiculus
55
Q

From what 2 locations do the descending autonomic pathways originate?

A
  • Reticular formation of the midbrain

- Hypothalamus

56
Q

What are the 2 modulatory descending tracts?

A
  • Catecholaminergic

- Serotonergic

57
Q

Where does the catecholaminergic tract descend the spinal cord?

A
  • Ventral-lateral portion of lateral funiculus
58
Q

From what in the higher centers do the catecholaminergic tracts originate from?

A
  • Nucleus subcoreuleus

- Locus coeruleus

59
Q

What neurotransmitter is used in the catecholaminergic tracts?

A

Norepinephrine

60
Q

What is the function of the catecholaminergic tract?

A
  • Modulates neuronal function
61
Q

What is the name of serotonergic tract?

A
  • Raphespinal
62
Q

What is the name of the catecholamingeric tract?

A
  • Ceruleospinal
63
Q

From where does the raphespinal tract originate?

A
  • Brain stem’s raphe nuclei
64
Q

Where does the raphespinal tract descend the spinal cord?

A
  • Ventral and lateral funiculus
65
Q

What is the function of the serotonergic tract?

A
  • Modulates neuronal function
66
Q

What 2 tracts make up the medial longitudinal fasciculus?

A
  • Medial vestibulospinal

- Pontine reticulospinal

67
Q

What is the origin of the medial vestibulospinal tract?

A
  • Superior and inferior vestibular nuclei
68
Q

What is the origin of the pontine reticulospinal tract?

A
  • Potine reticular nuclei
69
Q

Does the medial vestibulospinal tract cross?

A
  • Both crossed and uncrossed fibers
70
Q

Do the fibers of the pontine reticulospinal tract cross?

A
  • Mostly uncrossed
71
Q

What is the extent of the medial vestibulospinal tract?

A

Cervical and upper thoracic

72
Q

What is the extent of the pontine reticulospinal tract?

A

Entire cord

73
Q

What is the termination of the medial longitudinal fasciculus?

A
  • Anterior horn cells via interneurons
74
Q

What is the function of the medial vestibulospinal tract?

A
  • Reflex adjustments of the ihead in response to vestibular stimulation
75
Q

What is the function of the pontine reticulospinal tract?

A
  • Controls automatic movements
76
Q

What is the origin of the lateral vestibulospinal tract?

A
  • Lateral vestibular nuclei
77
Q

Do the fibers of the lateral vestibulospinal tract cross?

78
Q

What is the extent of the lateral vestibulospinal tract?

A

Entire cord

79
Q

What is the termination of the lateral vestibulospinal tract?

A

Anterior horn cells via interneurons and directly

80
Q

What is the function of the lateral vestibulospinal tract?

A
  • Increases phasic extensor tone

- Decreases flexor tone in proximal muscles

81
Q

What is the origin of the medullary reticulospinal tract?

A
  • Medullary reticular formation
82
Q

Do the fibers of the medullary reticulospinal tract cross?

A

Mostly no.

83
Q

What is the extent of the medullary reticulospinal tract?

A
  • Entire cord
84
Q

What is the termination of the medullary reticulospinal tract?

A
  • Anterior horn cells via interneurons and directly
85
Q

What is the function of the medullary reticulospinal tract?

A
  • Controls automatic movements
  • Increases flexor tone tonically
  • Decreases extensor tone
86
Q

What is the origin of the tectospinal tract?

A

The tectus of the midbrain

87
Q

Do the fibers of the tectospinal tract cross?

88
Q

What is the extent of the tectospinal tract?

A

Cervical region

89
Q

What is the termination of the tectospinal tract?

A

AHC direct and via interneurons

90
Q

What is the function of the tectospinal tract?

A
  • 2nd degree mediation of reflex postural movements (phasically) [termed cephalogyric reflexes]
  • Predominantly reflexive turning movements of the head and eyes
91
Q

What is the origin of the olivospinal tract?

A

The inferior olive

92
Q

Do the fibers of the olivospinal tract cross?

93
Q

What is the extent of the olivospinal tract?

A

Cervical region

94
Q

What is the termination of the olivospinal tract?

A

AHC directly and via interneurons

95
Q

What is the function of the olivospinal tract?

A

2nd degree coordination of head and eye phasic movements

96
Q

What is the origin of the rubrospinal tract?

A
  • Red nucleus in midbrain
97
Q

What is the origin of the pontospinal tract?

A
  • Pontine nucleus in reticular formation
98
Q

Do the fibers of the rubrospinal or pontospinal tracts cross?

99
Q

What is the extent of the rubrospinal tract?

A

Entire cord

100
Q

What is the extent of the pontospinal tract?

101
Q

What is the termination of the rubrospinal and pontospinal tract?

A
  • AHC via interneurons
102
Q

What is the function of the rubrospinal tract?

A
  • Voluntary movements of distal muscles
  • Decreases extensor tone
  • Increases flexor tone
103
Q

What is the function of the pontospinal tract?

104
Q

What is the origin of the lateral corticospinal tract?

A
  • Cerebral cortex
105
Q

Do the fibers of the lateral corticospinal tract cross?

106
Q

What is the extent of the lateral corticospinal tract?

A

Entire cord

107
Q

What is the termination of all volitional tracts?

A

AHC via interneurons

108
Q

What is the function of the lateral corticospinal tract?

A
  • Voluntary skill movements of limbs
  • Speed and agility
  • Modulation of sensory input
109
Q

What is the origin of the anterior corticospinal tract?

A
  • Cerebral cortex
110
Q

Do the fibers of the anterior corticospinal tract cross?

111
Q

What is the extent of the anterior corticospinal tract?

A

Entire cord

112
Q

What is the function of the anterior corticospinal tract?

A
  • Volitional movements of the deep back muscles, and modulation of sensory input
113
Q

What is the origin of the track of barnes?

A
  • Cerebral cortex
114
Q

Do the fibers of the track of branes cross?

115
Q

What is the extent of the track of barnes?

A

Entire cord

116
Q

What is the function of the track of branes/

A

Voluntary movements

Modulation of sensory input

117
Q

What is the origin of the autonomic tract?

A
  • Hypothalamus
118
Q

Do the fibers of the autonomic tract cross?

119
Q

What is the extent of the autonomic tract?

A

Thoracic and sacral

120
Q

What is the termination of the autonomic tract?

A

Beta cells of the lateral horn

121
Q

What is the functino of the autonomic tract?

A

Sympathetic and parasympathetic nervous system

122
Q

What is the origin of the ceruleospinal tract?

A
  • Locus ceruleus
    and
  • Nucleus subceruleus (reticular formation)
123
Q

What is the extent of the ceruleospinal tract?

A
  • Brain stem

- Entire spinal cord

124
Q

What is the termination of the ceruleospinal tract?

A
  • Intermediate gray and AHC

- Dorsal horn

125
Q

What is the function of the ceruleospinal tract?

A
  • Neuronal modulation

- Pain modulation

126
Q

What is the origin of the raphe-spinal tract?

A
  • BS Raphe nuclei
127
Q

What is the extent of the raphe-spinal tract?

A

Brain stem and entire SC

128
Q

What is the termination of the raphe-spinal tract?

A
  • Intermediate gray

- Dorsal horn

129
Q

What is the function of the raphe-spinal tract

A
  • Neuronal modulation

- Pain modulation

130
Q

What is the origin of the dopaminergic pathway?

A
  • Ventral tegmentum
131
Q

What is the extent of the dopaminergic pathway?

A
  • Lower brain stem

- Entire SC

132
Q

What is the termination of the dopaminergic pathway?

A
  • Intermediate grey and AHC

- Dorsal horn

133
Q

What is the function of the dopaminergic pathway?

A
  • Neuronal modulation
134
Q

What are central pattern generators?

A
  • Neural circuits that produce self-sustaining patterns of behavior in the absence of sensory input

Neuroscience (33 decks)

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