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Flashcards in Descending Tracts Deck (134):
1

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

- Cortical area 6

2

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

- Ventro-medial portion of intermediate gray matter

3

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

- Ventral, and ventral lateral funiculi

4

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

- Long propriospinal interneurons

5

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

- The ventral medial descending system is bilaterally distributed meaning left and right both contribute control to theleft and right

6

Why does the ventral medial descending system have many synapses?

- It has a high degree of collateralization

7

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

- Large groups of muscles are activated together

8

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

- Postural, and stabilization by synergistic action of axial and proximal muscles

9

What 5 tracts make up the ventral medial descending system?

- Lateral vestibulospinal
- Medial vestibulospinal
- Lateral reticulospinal (medullary)
- Medial reticulospinal (pontine)
- Tectospinal

10

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

- Long is medially located
- Short is laterally located

11

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

- Lateral reticulospinal --> Medullary
- Medial reticulospinal --> Pontine

12

Which reticulospinal tract is tonically active?

- Medial/ Pontine

13

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

- Extensors activated
- Flexors inhibited
- Drive upright posture

14

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

- Travels down ventral medial funiculus
- Enter gray matter, and synapse on alpha motor neurons

15

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

- Flexors activated
- Extensors inhibited

16

Which reticulospinal tract is more dominant?

- Medial

17

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

- Nuclei found within medulla
- Connected to vestibular system within inner ear

18

Which vestibular tract is not billateral?

The lateral

19

Which vestibular tract only has phasic properties?

- The lateral

20

Which vestibulospinal tract is monosynaptic?

The lateral

21

Is the lateral vestibulospinal tract ipsilateral or contralateral?

Ipsilateral

22

What is the origin of the tectospinal tract?

The tectum on the midbrain

23

What are the 2 lateral descending tracts?

- Rubrospinal
- Ponto spinal

24

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

- 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