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Neuro Anatomy > Test 2: Descending Spinal Paths > Flashcards

Test 2: Descending Spinal Paths Flashcards

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1
Q

What are the 3 main function classes of descending spinal pathways?

A

Voluntary movement- internal activation
Automatic movement- more complicated than reflexes; dont need sensory input
Reflex movement- sensory input with motor output

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2
Q

What is an UMN

A

Motor cortex in origin of a descending path that goes to brainstem/s.c. neurons

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3
Q

What is the function of the lateral corticospinal tract

A

independant finger pointing

  • monosynaptic
  • CB in cortex-> rexed IX
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4
Q

What is the function of the rubospinal tract?

A

gross movement of hand

-CB in red nucleus of midbrain-> rexed VII

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5
Q

What are the 2 paths in the lateral motor system

A

lateral corticospinal

rubrospinal

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6
Q

Whata re the 4 paths in the medial motor system

A

ventral corticospinal
reticulospinal x2 (pontine and medullary)
vertibulblospinal x2
tectospinal

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7
Q

What is the function of the ventral corticospinal tract

A

gross movement of head

  • proximal limb/axial muscle control
  • cortex to s.c
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8
Q

What is the function of the reticulospinal tracts

A

helps postural/anticipatory movement

  • pontine=postural control
  • medullary=locomotion
  • retic formation to s.c.
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9
Q

What is the function of the vestibulospinal tracts

A

posture of head relative to space

-vestib nucleus to s.c.

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10
Q

What is the function of the tectospinal tract

A

vision controlling neck movements

  • tectum to s.c.
  • CB superior colliculus to s.c.
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11
Q

What are LMNs

A

alpha and gamma neurons in brainstem motor nuclei or spinal motor pools
-excitable fibers that produce muscle force

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12
Q

What are gamma vs. alpha LMN?

What is coactivation?

A

gamma: muscle spindles- intrafusal fibers
alpha: muscle fibers producing force

activate together for proprioceptive feedback during contraction

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13
Q

What is indirect vs. direct control

A

pyramidal (lamina V)cells control LMN in brainstem or spinal cord– muscle spindles and fibers= direct

pyramidal UMN relay to second UMN in brainstem to then control LMN–initiaites/recruits brainstem UMN

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14
Q

What are examples of indirect motor control via brainstem UMN

A

Midbrain:
red nucleus- rubrospinal
superior colliculis- tectospinal

Pon/med:
reticular formation-reticulospinal tract
Vestibulonucleus

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15
Q

How do you classify direct control pathways based on the amount of synapses?

A

monosynaptic: one UMN to LMN
disynaptic: UMN to interneuron (Rex VII or VIII) to LMN
polysynap: UMN to >1 interneuron (Rex VII or VIII) to LMN

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16
Q

What are the 3 medial tracts of medial motor systems in cross sections? Where do they terminate?

A

ventral corticospinal
medial vestibulospinal
tectospinal–CO

all end in cervical

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17
Q

What are the 3 more lateral tracts of medial motor systems in cross sections? Where do they terminate?

A

medullary reticulospinal
pontine reticulospinal
lateral vestibulospinal

-all travel entire spinal cord

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18
Q

What is the BA for M1?

A

BA 4

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19
Q

What CB are in the M1?

A

lateral corticospinal tract

ventral corticospinal tract

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20
Q

What to the tracts from M1 do? What would a lesion cause?

A

Volunatary/discrete movements for manipulation/initial movements
-CB innervate multiple LMN pools to recruit agonits

Damage causes weakness

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21
Q

What is the BA for supplamentory motor area?

A

Pre-motor

BA 6

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22
Q

What is the function of tracts from the pre-motor cortex?

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A

intrinsic given motor commands/bilateral activity

automatic and anticapitory movements

23
Q

What does primary somatic sensory cortex help with?

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A

some post-central cortex contributes to sensory movement

24
Q

What is the cingulate motor area BA

25
What does the cingulate motor area function?
Emotive drive of LMN
26
What are PMd and SMA cortexes?
motor association areas - higher order integration - complex tasks PMD: anticapatory postural adjustments SMA:internally motivated and bimanual movement UMN recruits larger LMN pools compared to M1
27
How many synapses are in the lateralcorticospinal pathways
MONOsynaptic primarily; some di and poly | UMN from M1 to LMN in cervical spine
28
Where does the pyramidal cell in lateral corticospinal tract synapse?
Rexed IX lateral or medial motor pool - lateral pool to distal muscles - medial pool controls pelvic, trunk, and girdle
29
Where do the pyramidal cells decussate?q
pyramidal decussation | -Medullary-sc junction
30
After decussating in the pyramidal decussation where do the pyramidal cells travel in lateral corticospinal path
descend contralateral lateral corticospinal tract | synapse on LMN/interneuron in LATERAL motor column
31
Where are the CB in the rubrospinal tract? Where do they decussate?
Red nucleus | Decussate immediately in midbrain ventral tegmentum
32
Where do the rubrospinal neurons travel after decussating in the midbrain ventral tegmentum?
Lateral border of pons/medullary tegmentum Join LCST path in LATERAL feniculus/column -go to intermed zone Rex IV or VII interneurons
33
Where is the ventral corticospinal tract CB and where does it go?
10-15% of CST that DONT decussate | From M1 to bilatearl rex VII
34
Where does the ventral corticospinal tract travel down to the spinal cord?
Down ventral feniculus Decussates at level in C-spine to synapse bilateral Rex VII -Stops in C-spine -all poly or disynap
35
Where does the ventral corticospinal decussate in the spinal cord?
Ventral commisure- rex VII
36
What are the functions of the reticulospinal pathways
Autonomic postural adjustments- heterogenous collection of neurons Pontine: postural Medullary: locomotion
37
Where do the reticulospinal and tectospinal tracts travel?
ALL central in the medial feniculus
38
Where are the CB of tectospinal
superior colliculus
39
Where does tectospinal decusate
central tegmentum of midbrain
40
Where does the tectospinal path go after decussation
down tectospinal tract to cervial cord
41
Where are the CB of the pontine reticulospinal
prontine reticular formation | -stays ipsilateral
42
Where does the pontine reticulospinal travel?
medial down entire spinal cord in rexed VII -down central tegmentum for POSTURAL
43
Where are the CB of medullar reticulospinal?
medullary reticular formation | -stays ipsilateral
44
Where does the medullary reticulospinal travel?
descend central tegmentum to entire s.c. decussates in spinal grey at level LOCOMOTION
45
What is different about motor columns in the thoracic spine?
No lateral motor columns | -no limbs!
46
What are motor pools
alpha and gamma motor neurons for ONE muscle | ex: motor pool C5-7 for biceps
47
What are propriospinal neurons? Where are they?
In Rexed Vii - connect and coordinate recruitment with many motor pools - activates multiple SSC segments
48
What are commisural neurons
propriospinal neurons that coordinate motor pools bilaterally - located medial= postural control - located lateral= limb movements
49
What are gamma motor neurons? Why is their coactivation important?
muscle spindle - control spindle length and register stretches even during contraction - efferent axons sit at end of spindle past the afferents
50
What are long distance spinal circuits?
propriospinal circuits for proximal motor pools of UE and LE | Help muscles for posture
51
What are short distance local circuits?
propriospinal in same close together | muscle synergies to coordinate pools in local areas
52
What is the relex control spinal reflex
When Adelta or C fibers are activated via noxious simultation-> cutaneous reflex circuit ONLY activate alpha NOT gamma
53
What is the flexor withdrawl of the spinal reflex
limb pulls away from stimulus - interneurons recruited to excite ipsilateral LMN- flex - interneurons inhibit ipsilateral extensor neurons - allows quick withdraw
54
What is the crossed extensory spinal reflex
takes body weight and helps balance - decusstes of interneuron to recruit contralateral excitatory reponse - LMN control extensors- excites - inhibits contrlateral flexors

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