Descending Tracts Flashcards
(134 cards)
1
Q
What area does the ventral medial descending system primarily receive fibers from?
A
- Cortical area 6
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
3
Q
What funiculi are the tracts of the ventral medial descending system located within?
A
- Ventral, and ventral lateral funiculi
4
Q
What type of interneurons do the tracts of the ventral medial descending system synapse on?
A
- Long propriospinal interneurons
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
6
Q
Why does the ventral medial descending system have many synapses?
A
- It has a high degree of collateralization
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
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
9
Q
What 5 tracts make up the ventral medial descending system?
A
- Lateral vestibulospinal
- Medial vestibulospinal
- Lateral reticulospinal (medullary)
- Medial reticulospinal (pontine)
- Tectospinal
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
11
Q
What are the alternate names of the medial and lateral reticulospinal tracts?
A
- Lateral reticulospinal –> Medullary
- Medial reticulospinal –> Pontine
12
Q
Which reticulospinal tract is tonically active?
A
- Medial/ Pontine
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
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
15
Q
What muscle groups are activated and inhibited by the lateral/ medullary reticulospinal tract?
A
- Flexors activated
- Extensors inhibited
16
Q
Which reticulospinal tract is more dominant?
A
- Medial
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
18
Q
Which vestibular tract is not billateral?
A
The lateral
19
Q
Which vestibular tract only has phasic properties?
A
- The lateral
20
Q
Which vestibulospinal tract is monosynaptic?
A
The lateral
21
Q
Is the lateral vestibulospinal tract ipsilateral or contralateral?
A
Ipsilateral
22
Q
What is the origin of the tectospinal tract?
A
The tectum on the midbrain
23
Q
What are the 2 lateral descending tracts?
A
- Rubrospinal
- Ponto spinal
24
Q
Which of the 2 lateral descending systems originate from the reticular formation?
A
- Pontospinal
25
Where is area 6?
- Anterior to the central sulcus
26
Where is area 4?
- The precentral gyrus
27
From what area in the cortex do the fibers of the lateral descending system originate from?
Area 4
28
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?)
Contralateral representation
29
Where is the lateral system found in the gray matter of the cerebrum?
- Lateral and dorsal portions of intermediate gray
30
Where is the lateral descending system found the medulla?
- Dorsal-laterally
31
Where is the lateral descending system found in the spinal cord?
The lateral funiculus
32
What types of neurons are found in the intermediate gray?
Short propriospinal interneurons
33
Where does the rubrospinal tract originate from?
The red nucleus
34
Does the rubrospinal tract innervate proximal or distal musculature?
Distal
35
Does the rubrospinal tract provide discrete or gross control?
Discrete
36
What is the major function of the rubrospinal tract?
Fractionalizes movement, especially of distal musculature
37
What will a lesion of the rubrospinal tract cause?
- Decreased dexterity of fingers and distal musculature
38
Does the rubrospinal tract drive flexors or extensors?
Flexors
39
From where does the pyramidal system originate?
- Directly from cerebral cortex
40
Where is the pyramidal system located in the spinal cord? (x-section)
- Laterally
41
How much collateralization is found in the pyramidal system?
Very little
42
What systems does the pyramidal system feed into?
- Ventral and lateral
43
What are the 2 main functions of the pyramidal tract?
- Voluntary control
| - Very highly fractionalized movement
44
What special types of movements are the pyramidal tracts involved in?
- Movements that require learning and selection
45
What effect does the pyramidal system have on sensory input?
Modulation (especially at the dorsal horn)
46
What representation does the pyramidal system have?
Contrallateral
47
What percent of the pyramidal system goes to the lateral cell column? The medial?
85 % lateral
| 15 % medial
48
Which system is most responsible for pathology in humans?
The pyramidal system
49
What are the 3 tracts of the pyramidal system?
- Lateral corticospinal
- Anterior corticospinal
- Tract of barnes
50
What is another name for the pyramidal system?
Volitional
51
What are some results of a lesion to the pyramidal system?
- LMNS
- Decreased muscle tone
- Decreased cutaneous reflexes
- Slow tendon reflexes
- Decreased initiation and execution of movement (especially digits)
- Weakness
- Fatigability
52
Where do the tracts of the pyramidal system split?
In the spinal cord
53
What is the tract of barnes?
The ~ 2 % of the pyramidal system that stays ipsilateral through the spinal cord
54
Where are the descending autonomic pathways located?
- Ventral and lateral funiculus
55
From what 2 locations do the descending autonomic pathways originate?
- Reticular formation of the midbrain
| - Hypothalamus
56
What are the 2 modulatory descending tracts?
- Catecholaminergic
| - Serotonergic
57
Where does the catecholaminergic tract descend the spinal cord?
- Ventral-lateral portion of lateral funiculus
58
From what in the higher centers do the catecholaminergic tracts originate from?
- Nucleus subcoreuleus
| - Locus coeruleus
59
What neurotransmitter is used in the catecholaminergic tracts?
Norepinephrine
60
What is the function of the catecholaminergic tract?
- Modulates neuronal function
61
What is the name of serotonergic tract?
- Raphespinal
62
What is the name of the catecholamingeric tract?
- Ceruleospinal
63
From where does the raphespinal tract originate?
- Brain stem's raphe nuclei
64
Where does the raphespinal tract descend the spinal cord?
- Ventral and lateral funiculus
65
What is the function of the serotonergic tract?
- Modulates neuronal function
66
What 2 tracts make up the medial longitudinal fasciculus?
- Medial vestibulospinal
| - Pontine reticulospinal
67
What is the origin of the medial vestibulospinal tract?
- Superior and inferior vestibular nuclei
68
What is the origin of the pontine reticulospinal tract?
- Potine reticular nuclei
69
Does the medial vestibulospinal tract cross?
- Both crossed and uncrossed fibers
70
Do the fibers of the pontine reticulospinal tract cross?
- Mostly uncrossed
71
What is the extent of the medial vestibulospinal tract?
Cervical and upper thoracic
72
What is the extent of the pontine reticulospinal tract?
Entire cord
73
What is the termination of the medial longitudinal fasciculus?
- Anterior horn cells via interneurons
74
What is the function of the medial vestibulospinal tract?
- Reflex adjustments of the ihead in response to vestibular stimulation
75
What is the function of the pontine reticulospinal tract?
- Controls automatic movements
76
What is the origin of the lateral vestibulospinal tract?
- Lateral vestibular nuclei
77
Do the fibers of the lateral vestibulospinal tract cross?
No
78
What is the extent of the lateral vestibulospinal tract?
Entire cord
79
What is the termination of the lateral vestibulospinal tract?
Anterior horn cells via interneurons and directly
80
What is the function of the lateral vestibulospinal tract?
- Increases phasic extensor tone
| - Decreases flexor tone in proximal muscles
81
What is the origin of the medullary reticulospinal tract?
- Medullary reticular formation
82
Do the fibers of the medullary reticulospinal tract cross?
Mostly no.
83
What is the extent of the medullary reticulospinal tract?
- Entire cord
84
What is the termination of the medullary reticulospinal tract?
- Anterior horn cells via interneurons and directly
85
What is the function of the medullary reticulospinal tract?
- Controls automatic movements
- Increases flexor tone tonically
- Decreases extensor tone
86
What is the origin of the tectospinal tract?
The tectus of the midbrain
87
Do the fibers of the tectospinal tract cross?
Yes
88
What is the extent of the tectospinal tract?
Cervical region
89
What is the termination of the tectospinal tract?
AHC direct and via interneurons
90
What is the function of the tectospinal tract?
- 2nd degree mediation of reflex postural movements (phasically) [termed cephalogyric reflexes]
- Predominantly reflexive turning movements of the head and eyes
91
What is the origin of the olivospinal tract?
The inferior olive
92
Do the fibers of the olivospinal tract cross?
Yes
93
What is the extent of the olivospinal tract?
Cervical region
94
What is the termination of the olivospinal tract?
AHC directly and via interneurons
95
What is the function of the olivospinal tract?
2nd degree coordination of head and eye phasic movements
96
What is the origin of the rubrospinal tract?
- Red nucleus in midbrain
97
What is the origin of the pontospinal tract?
- Pontine nucleus in reticular formation
98
Do the fibers of the rubrospinal or pontospinal tracts cross?
Unknown
99
What is the extent of the rubrospinal tract?
Entire cord
100
What is the extent of the pontospinal tract?
Unknown
101
What is the termination of the rubrospinal and pontospinal tract?
- AHC via interneurons
102
What is the function of the rubrospinal tract?
- Voluntary movements of distal muscles
- Decreases extensor tone
- Increases flexor tone
103
What is the function of the pontospinal tract?
Unknown
104
What is the origin of the lateral corticospinal tract?
- Cerebral cortex
105
Do the fibers of the lateral corticospinal tract cross?
Yes
106
What is the extent of the lateral corticospinal tract?
Entire cord
107
What is the termination of all volitional tracts?
AHC via interneurons
108
What is the function of the lateral corticospinal tract?
- Voluntary skill movements of limbs
- Speed and agility
- Modulation of sensory input
109
What is the origin of the anterior corticospinal tract?
- Cerebral cortex
110
Do the fibers of the anterior corticospinal tract cross?
Yes
111
What is the extent of the anterior corticospinal tract?
Entire cord
112
What is the function of the anterior corticospinal tract?
- Volitional movements of the deep back muscles, and modulation of sensory input
113
What is the origin of the track of barnes?
- Cerebral cortex
114
Do the fibers of the track of branes cross?
No
115
What is the extent of the track of barnes?
Entire cord
116
What is the function of the track of branes/
Voluntary movements
| Modulation of sensory input
117
What is the origin of the autonomic tract?
- Hypothalamus
118
Do the fibers of the autonomic tract cross?
No
119
What is the extent of the autonomic tract?
Thoracic and sacral
120
What is the termination of the autonomic tract?
Beta cells of the lateral horn
121
What is the functino of the autonomic tract?
Sympathetic and parasympathetic nervous system
122
What is the origin of the ceruleospinal tract?
- Locus ceruleus
and
- Nucleus subceruleus (reticular formation)
123
What is the extent of the ceruleospinal tract?
- Brain stem
| - Entire spinal cord
124
What is the termination of the ceruleospinal tract?
- Intermediate gray and AHC
| - Dorsal horn
125
What is the function of the ceruleospinal tract?
- Neuronal modulation
| - Pain modulation
126
What is the origin of the raphe-spinal tract?
- BS Raphe nuclei
127
What is the extent of the raphe-spinal tract?
Brain stem and entire SC
128
What is the termination of the raphe-spinal tract?
- Intermediate gray
| - Dorsal horn
129
What is the function of the raphe-spinal tract
- Neuronal modulation
| - Pain modulation
130
What is the origin of the dopaminergic pathway?
- Ventral tegmentum
131
What is the extent of the dopaminergic pathway?
- Lower brain stem
| - Entire SC
132
What is the termination of the dopaminergic pathway?
- Intermediate grey and AHC
| - Dorsal horn
133
What is the function of the dopaminergic pathway?
- Neuronal modulation
134
What are central pattern generators?
- Neural circuits that produce self-sustaining patterns of behavior in the absence of sensory input
