Upper motor neurons

organization of corticospinal tract

100

Upper motor neurons start in...

cell bodies are derived from all regions of...

the cerebral cortex (correct answer for both) 

200

There are especially high concentrations of UMN found in what parts of the cerebral cortex? 

precentral gyrus and paracentral lobule 

300

axons projected directly to LMNs and interneurons in brainstem and spinal cord for the  purpose of...

initiating and regulating voluntary movements 

400

axons going to spinal motor nuclei form what tract? 

axons going to the brainstem motor nuclei form what tract? 

-corticospinal (aka pyramidal) tract

-corticobulbar tract (aka extrapyramidal) 

500

where is the highest concentration of UMN? (name cortexes) 

primary motor cortex, premotor cortex and somatosensory cortex 

UMN control

100

UMN cell bodies live in___ and axons flow down to ____ in the ____ or _____. 

UMN in the corticobulbar tract synapse with neurons in the _______ or ______. 

the motor cortex, synapse in the brainstem or spinal cord. 

red nucleus or the reticular formation 

200

what is the pathway that UMNs follow? 

starting at the corona radiate, internal capsule, cerebral peduncle, finally synapse in the midbrain, pons, medulla or spinal cord 

300

which part controls contralateral upper limb movement? 

dorsolateral precentral gyrus 

400

which part is the representation on homunculus for contralateral lower limb movement? 

anterior parts of paracentral lobule 

500

what is the exaggerated myotactic reflex? 

what is the babinski reflex? 

• exaggerated patellar reflex
• Response greater in speed and amplitude as a result of reduced threshold of excitability of stretch receptors
• Toes normally curl down when their foot is stroked, when the babinksi reflex is present the big toe points up and toes fan out 

corticospinal/corticobulbar tract

100

In the lateral corticospinal tract..

at the pons level what happens? 

at the medullary level is the formation of...

at the caudal medulla what happens? 

-pyramidal bundles become medialized

- MEDULLARY PYRAMIDS (rostral 2/3 of medulla)

-pyramidal crossover (90%) pass dorsolaterally to form the LATERAL CORTICOSPINAL TRACT

Descends through all SPINAL CORD levels in the DORSAL half of the lateral funiculus

200

describe the pathway of the corticobular tract 

-Originate primarily from VENTRAL PART of PRECENTRAL GYRUS (face/vocal tract representation) 

-Passes through CORONA RADIATA and INTERNAL CAPSULE (like corticospinal tract) 

-Corticobulbar fibers terminate and cross over at all levels of the BRAINSTEM

300

the remaining 10% continue ______ as what tract? 

ipsilaterally as the ventral corticospinal tract 

400

the remaining 10% of pyramidal fibers cross in the _____at the same level or termination. 

ventral white commissure 

500

PTN (pyramidal tract) projections to limbs are considered to be a _____ system. 

completely crossed 

pyramidal tract

100

exception of canal nucleus representations : remaining LMNs of the brainstem are supplied BILATERALLY (receive input from UMN both sides of body) by motor cortex

-the upper face has what kind of innervation?

-the lower face has what kind of innervation? 

-upper face: bilateral

-lower face: contralateral (only) 

200

what is the function of the pyramidal system? 

Stimulation of MI (primary motor cortex)  activates the pyramidal system, resulting in the excitation of CONTRALATERAL LMN and the contraction of individuals muscles on that side

300

UMN in the MI command 3 components of voluntary movement, what are they? 

-speed of movement

-force of muscle contraction

-direction of movement 

400

impulse activities in MI increase several hundred milliseconds ____

• _____ with the increased force required for the dynamic phase of the movement
• _______ somewhat during any tonic, holding phase of movement (crease UMN activity if flexing or holding a movement)

before movement initiation

-accelerates 

-Decreases

500

activity results from 3 inputs to MI

• 1. CORTICAL-CORTICAL PROJECTIONS from primary SI and secondary (SII) SOMATOSENSORY CORTICAL AREAS in the parietal lobe posteriorly
• 2. Premotor cortex anteriorly (including supplementary motor cortex)
• 3. Projections from motor nuclei in the THALAMUS

MISC

100

SOMATOSENSORY INPUTS provide 

SUPPLEMENTARY motor area (SMA) organizes SELF-INITIATED MOVEMENT SEQUENCES and transmits them to MI for EXECUTION THALAMIC nuclei. what does the thalamic nuclei do? 

somatotopically organized proprioceptive (muscle) and exteroceptive (cutaneous- skin) information occurring as a result of movement eg. Hand area of SI projects to the hand area of MI

• 1. Provide direction form the cerebellum to the UMN for controlling rapidly executed, highly skilled movement
• 2. Transmite the output of the basal ganglia to the premotor areas

200

Pyramidal tract susceptible to vascular and traumatic damage at ANY CNS LEVEL because....

Its numerous MYELINATED nerve fibers make it MORE SUSCEPTIBLE to_____ such as MS or ALS

it runs through the entire brain and spinal cord (a lot of area that can be damaged

-demyelinating diseases 

300

• Principles signs of UMN syndrome (all in the contralateral limbs)

• Absence of volitional movement (paralysis)
• Increased muscle tone
• Exaggerated myotactic reflexes
• Extensor plantar response

400

what is the Clasp knife response?

what is flaccid paralysis?

what is hypotonia? 

what is severe hypertonia? (spasticity) 

• Sudden collapse of all resistance while a muscle is rapidly stretched
• Characteristic of the increased resistance seen in spasticity
• low tone, hypotonia, LMNs
• increased muscle tone (manifested by increased resistance to passive stretch, especially in the antigravity muscles (flexors of the arm and fingers and the extensors of the leg)
• If accompanied by LOSS OF VOLITIONAL movements CONTRALATERALLY, it’s called spastic hemiplegia

500

• Know the difference between supranuclear, nuclear, and infranuclear lesions with regard to UMNs and LMNs

• Lesion of UMN aka SUPRANUCLEAR LESION because damage occurs in the pathway carrying impulses to the LMN
• A lesion in the LMN- called NUCLEAR LESION- when the neuronal cell bodies are involved and an INFRANUCLEAR LESION when the LMN axons are involved