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Supraspinal Motor
| Question | Answer |
|---|---|
| The phylogenetically older medial pathways control what? | extensors, axial and proximal muscles for control of posture and balance |
| Lateral pathways control what types of muscles? | flexors, distal muscles for fine motor control |
| List medial pathways | vestibULOspinal, reticULOspinal, descending MLF |
| List lateral pathways | rubrospinal, lateral and ventral corticospinal, tectospinal |
| The descending MLF that goes to extensors in the arms originates where? | medial vestibular nucleus |
| Projections from the lateral vestibular nucleus descend within what tract and innervate what? | vestibulospinal tract; extensor alpha motoneuron pools at all levels down to lumbosacral |
| Origins of the medial and lateral reticulospinal tracts: | medial RS tract - pons (medial boob) lateral RS tract - medulla |
| Lateral reticulospinal tract is (excitatory/inhibitory) on extensor gamma motoneurons in the arms or legs. | inhibitory |
| True/False: The right medial reticulospinal tract excites the L side extensor muscles of arms and legs. | False: medial RS tract excites both side arms and legs |
| Which 2 supraspinal tracts decussate in the midbrain? | rubrospinal and tectospinal |
| Both lat and med RS tracts receive input from the cerebral cortex, but which receives input from ascending spinoreticular sources? | medial RS tract |
| function of tectospinal tract | head and trunk positioning in response to visual stimuli (each side innervates bilaterally @ target level) |
| rubrospinal tract function (hint: lateral pathway) | upper limb movement, magnocellular populations excite flexors in hands |
| cortical origin(s) for lateral corticospinal tract | primary motor cortex AND primary somatic sensory cortex |
| List how indirect control of motoneurons occurs in both lateral and ventral corticospinal tracts. | lateral - synapses on red nucleus, descends with rubrospinal ventral - synapses with reticular formations, descends with retiulospinal (corticoreticulospinal tract) |
| Stroke of this area could easily cause a complete hemiparesis due to the small amt of space all corticospinal tracts are packed into. | internal capsule |
| Corticobulbar fibers deccusate where? | at the level of the brainstem of the respective CN nucleus |
| Which corticofugal first order neuron cell bodies reside most medially in the cerebral cortex? | corticospinal, specifically toes, feet, etc. |
| What is the general hierarchy of cortical neurons giving motor commands? | supplementary motor to premotor to primary motor cortex |
| Intent to initiate planned movement on cue such as a specific patterned finger movement when a light flashes involves input from which cortices? | premotor and primary motor cortices |
| What has the most recent research shown to be erroneous about how we related the homunculus to cortical mapping? | electrical stimulation of the cortex at the location of a specific region doesn't necessarily activate one specific muscle group, but rather a group of muscles that would work synergistically towards purposeful movement in a specific direction |
| take-home message of microstimulation of primary motor cortex | microstimulating a certain spot of the motor cortex will recruit whatever muscles are necessary to make a monkey move its arm from where the experimenter holds it in space back to its mouth, for example |
| Which type of motor neuron lesion is characterized by minimally diminished fine motor control? | LMN lesion |
| True/False: Hyperreflexia seen in LMN lesions can spread spatially to other muscle neuron groups when a tendon is stretched. | False: UMN lesions show this - patellar tendon stretch = quadriceps contract, foot extends and maybe other side's leg kicks out |
| What type of pt should have a positive Babinski sign? | A newborn without fully myelinated tracts AND anyone with a spinal cord injury causing LMN syndrome in foot/toe extensors |
| The term "spasticity" implies what? | UMN syndrome with hyperreflexia and hypertonia |
| Explain the mechanism behind decerebrate posturing. | upper pons or midbrain lesion terminates rubrospinal and corticospinal antagonist input on vestibulo- and reticulospinal pathways, so the latter have free reign and cause elbow and leg extension with wrist, finger and plantar flexion |
| Why does the medullary reticulospinal tract not equal out the signal from the pontine tract that innervates extensors? | pontine reticulospinal neurons are being excited continually by spinoreticular afferents and this overall signal is greater than the medullary reticulospinal tract signals |
| Explain why the arms are flexed in decorticate posturing. | The rubrospinal tract is spared and these neurons synapse on alpha motoneuron pools for flexors only through the cervical cord |
| Where does one expect a lesion or injury to be localized if the pt is displaying decorticate posturing? | anywhere rostral to the red nuclei of the midbrain such as a cerebral cortical lesion |
Created by:
sirprakes
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