Test 2: Descending Spinal Paths Flashcards
What are the 3 main function classes of descending spinal pathways?
Voluntary movement- internal activation
Automatic movement- more complicated than reflexes; dont need sensory input
Reflex movement- sensory input with motor output
What is an UMN
Motor cortex in origin of a descending path that goes to brainstem/s.c. neurons
What is the function of the lateral corticospinal tract
independant finger pointing
- monosynaptic
- CB in cortex-> rexed IX
What is the function of the rubospinal tract?
gross movement of hand
-CB in red nucleus of midbrain-> rexed VII
What are the 2 paths in the lateral motor system
lateral corticospinal
rubrospinal
Whata re the 4 paths in the medial motor system
ventral corticospinal
reticulospinal x2 (pontine and medullary)
vertibulblospinal x2
tectospinal
What is the function of the ventral corticospinal tract
gross movement of head
- proximal limb/axial muscle control
- cortex to s.c
What is the function of the reticulospinal tracts
helps postural/anticipatory movement
- pontine=postural control
- medullary=locomotion
- retic formation to s.c.
What is the function of the vestibulospinal tracts
posture of head relative to space
-vestib nucleus to s.c.
What is the function of the tectospinal tract
vision controlling neck movements
- tectum to s.c.
- CB superior colliculus to s.c.
What are LMNs
alpha and gamma neurons in brainstem motor nuclei or spinal motor pools
-excitable fibers that produce muscle force
What are gamma vs. alpha LMN?
What is coactivation?
gamma: muscle spindles- intrafusal fibers
alpha: muscle fibers producing force
activate together for proprioceptive feedback during contraction
What is indirect vs. direct control
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
What are examples of indirect motor control via brainstem UMN
Midbrain:
red nucleus- rubrospinal
superior colliculis- tectospinal
Pon/med:
reticular formation-reticulospinal tract
Vestibulonucleus
How do you classify direct control pathways based on the amount of synapses?
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
What are the 3 medial tracts of medial motor systems in cross sections? Where do they terminate?
ventral corticospinal
medial vestibulospinal
tectospinal–CO
all end in cervical
What are the 3 more lateral tracts of medial motor systems in cross sections? Where do they terminate?
medullary reticulospinal
pontine reticulospinal
lateral vestibulospinal
-all travel entire spinal cord
What is the BA for M1?
BA 4
What CB are in the M1?
lateral corticospinal tract
ventral corticospinal tract
What to the tracts from M1 do? What would a lesion cause?
Volunatary/discrete movements for manipulation/initial movements
-CB innervate multiple LMN pools to recruit agonits
Damage causes weakness
What is the BA for supplamentory motor area?
Pre-motor
BA 6
What is the function of tracts from the pre-motor cortex?
intrinsic given motor commands/bilateral activity
automatic and anticapitory movements
What does primary somatic sensory cortex help with?
some post-central cortex contributes to sensory movement
What is the cingulate motor area BA
24, 31, 23
What does the cingulate motor area function?
Emotive drive of LMN
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
How many synapses are in the lateralcorticospinal pathways
MONOsynaptic primarily; some di and poly
UMN from M1 to LMN in cervical spine
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
Where do the pyramidal cells decussate?q
pyramidal decussation
-Medullary-sc junction
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
Where are the CB in the rubrospinal tract? Where do they decussate?
Red nucleus
Decussate immediately in midbrain ventral tegmentum
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
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
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
Where does the ventral corticospinal decussate in the spinal cord?
Ventral commisure- rex VII
What are the functions of the reticulospinal pathways
Autonomic postural adjustments- heterogenous collection of neurons
Pontine: postural
Medullary: locomotion
Where do the reticulospinal and tectospinal tracts travel?
ALL central in the medial feniculus
Where are the CB of tectospinal
superior colliculus
Where does tectospinal decusate
central tegmentum of midbrain
Where does the tectospinal path go after decussation
down tectospinal tract to cervial cord
Where are the CB of the pontine reticulospinal
prontine reticular formation
-stays ipsilateral
Where does the pontine reticulospinal travel?
medial down entire spinal cord in rexed VII
-down central tegmentum
for POSTURAL
Where are the CB of medullar reticulospinal?
medullary reticular formation
-stays ipsilateral
Where does the medullary reticulospinal travel?
descend central tegmentum to entire s.c.
decussates in spinal grey at level
LOCOMOTION
What is different about motor columns in the thoracic spine?
No lateral motor columns
-no limbs!
What are motor pools
alpha and gamma motor neurons for ONE muscle
ex: motor pool C5-7 for biceps
What are propriospinal neurons? Where are they?
In Rexed Vii
- connect and coordinate recruitment with many motor pools
- activates multiple SSC segments
What are commisural neurons
propriospinal neurons that coordinate motor pools bilaterally
- located medial= postural control
- located lateral= limb movements
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
What are long distance spinal circuits?
propriospinal circuits for proximal motor pools of UE and LE
Help muscles for posture
What are short distance local circuits?
propriospinal in same close together
muscle synergies to coordinate pools in local areas
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
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
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
