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NB DLA 18: Other Motor Pathways
Terms in this set (36)
Apart from the Corticobulbar and the Corticospinal tracts what are the other 5 descending pathways that influence motor activity?
These play a major role in coordinating ........ motor activity
These pathways arise from the ..........
2- Lateral Reticulospinal
3- Medial Reticulospinal
4- Lateral Vestibulospinal
5- Medial Vestibulospinal
Apart from the Lateral corticospinal tract what are two other pathways that influence flexion?
1- Rubrospinal tract
2- Lateral Reticulospinal tract
The Rubrospinal tract arises from the neurons of the ..........
Axons then, immediately, cross the midline in the ...... and descend to the .........., up to the ....... level
It then ends by synapsing on the ......... motor neurons on the ....... aspect of the Ventral horn cells
Does this tract have cortical input?
Contralateral spinal Cord
Alpha and Gamma
The Primary action of the Rubrospinal tract is to .........
Facilitate flexion in the upper limbs
The Fibers of the Lateral (medullary) Reticulospinal tract arise from the ...... neurons located in the medial 2/3 of the .....
The fibers descend to ........ levels of the Spinal cord
The Fibers end on ........... that synapse on ........ motor neurons in the Ventral horn of the spinal cord
Does this tract receive cortical input?
Alpha and Gamma
YES - bilaterally
The Major function of the Lateral (medullary) Reticulospinal tract is to ............ and ............
Powerfully suppress Extensor spinal reflex activity
Facilitate contraction of flexors
Flexor Pathways : Characteristics Summary
To recap, mention the following for each of the three flexor biased pathways:
The Medial (Pontine) Reticulospinal Tract arises from the ..... nucleus
It descends to the ..... (ips or cont) side of the Spinal cord
It Communicates with the .... motor neurons in the spinal cord
Does it receive cortical input?
YES - bilaterally through the corticoreticular fibers
The Medial (Pontine) Reticulospinal Tract also receives projections through the ...... tract
-This is a sensory tract
The Principal function of the Medial (Pontine) Reticulospinal Tract is to facilitate Axial and Limb .... muscles
The spinoreticular tract is the ........ pathway, formed by collateral branches from axons running in the ........
These collaterals end in the reticular nuclei in .........
Pons and Medulla
The Spinoreticular tract relays .... information to .... nuclei about ... , ... and crude .... in the trunk and limbs on the .... side
The Spinoreticular tract exerts an .... (excit or inhib) influence predominantly on the .......... nuclei, responsible for facilitating contraction of the .... muscles of the limb and trunk
The Lateral Vestibulospinal tract arises from the ...... nucleus
It has input from the ......... and .......
Does it have cortical input?
Inner ear and Cerebellum
The Lateral Vestibulospinal tract descends ....... to .... levels of the Spinal cord
The Lateral Vestibulospinal tract synapses with the ........... motor neurons of the Axial and Limb Extensor (anti-gravity muscles) thus plays a major role in regulating ...... related muscular responses?
The Medial Vestibulospinal tract arises from the .... nucleus
It has input from ..... and ....
Does it have cortical input?
Inner ear and Cerebellum
In the Medial Vestibulospinal tract axons descend .... (ips/cont) in the Spinal cord as the caudal extension of the MLF?
The Medial Vestibulospinal tract synapses with the ... motor neurons of the ...... and ....... levels of the spinal cord
It plays a role in facilitating muscular contraction of ... in coordination with ... movement thus plays a role in ........
Cervical and upper thoracic
Motor Pathways : Characteristics
For the three extensor biased pathways, list the following:
Alpha motor neurons innervate .... muscle fibers while Gamma motor neurons innervate ...... muscle fibers
•Alpha and gamma motor neurons are activated by higher centers so that the sensitivity of muscle spindles to stretch is maintained
-Both are activated in voluntary muscle activity
Both are lower motor neurons
When Extrafusal fibers (alpha motor neuron) contract, the intrafusal fibers (gamma motor neuron) become ........., meaning they ....
In this state the fibers are unable to measure subsequent changes in the .........
Gamma motor neurons give innervation to the contractile poles of the ... fibers
When they fire they cause these fibers to ... , thus .... the ....
•In this state the muscle spindle is able to detect muscular stretch
In Gamma loop, Intrafusal fibers of the muscle spindle play a role in .......
In the Gamma loop, the Alpha motor neurons innervates the ..... muscle fibers and the Gamma motor neurons innervate ..... fibers
The Purpose of Co-activation of the Alpha and Gamma motor neurons is, to ensure that contraction of the .... fibers is tuned to allow the neuromuscular spindle to measure stretching of the muscle
Abnormal posturing is common in a .... patient, either spontaneously or in response to pain
What are the 2 types of Abnormal posturing?
1- Decorticate posturing
2- Decerebrate posturing
In Decorticate posturing, what is the positioning of the upper and lower limbs?
at the elbows
In Decerebrate posturing, what is the positioning of the upper and lower limbs?
Both are extended
Extensor posturing arms are stiffly extended and held close to the body and the wrists are flexed outward indicates damage to midbrain or brain stem
In Decorticate posturing, where is the lesion?
What tracts are interrupted by this lesion? (2)
Above the RED NUCLEUS
-The red nucleus is at the midbrain
Corticospinal and Corticobulbar
In Decorticate posturing, as a result of Corticospinal fibers being interrupted, ......... is impaired
In Decorticate posturing, as a result of Corticobulbar fibers being interrupted, ......... occurs
Paralysis of motor CN
In decorticate posturing, why is there flexion of the upper limbs? Why is there extension of the lower limbs?
Flexion due to the Rubrospinal tract being intact
-Strong influences flexion in the upper limb
*The Lateral and Medial Vestibulospinal tracts are not able to overcome the effect of the Rubrospinal tract thus net flexion occurs
In the Lower limbs the Rubrospinal tract (flexion) is not present so there is net extension
-Extension due to the lateral and medial reticulospinal tracts
In Decerebrate posturing, where is the lesion?
What tracts are interrupted due to this lesion?
Below the RED NUCLEUS
-This is at the midbrain
In decerebrate posturing, why are the upper and lower limbs extended?
We lost the effects of Rubrospinal tract thus the Lateral Vestibulospinal and Medial Reticulospinal tracts take control of the Upper limbs causing extension
the Lateral Vestibulospinal and Medial Reticulospinal tracts take control of the Upper limbs causing extension of the lower limbs
Decorticate and Decerebrate posturing
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