Lecture 9- Motor Systems, Cortical Pathways Flashcards
What are the 4 functions of the motor system
- goal of movement and movement planning that best achieves the goal
- squencing of muscle contraction to smoothly and accurately achieve goal
- execution of goal-directed movement
- mechanics of the whole body and adjusts postural responses in adaptive ways for movement
the motor system is _____ motor control from the cortex and is the control of discrete ______ _____
- decending
- voluntary movements
what is motor homunclus?
disproportionate representation of hands, face and mouth in primary motor cortex
upper motor neuron (UMN) is the ___ order neuron
1st
UMN carries information from ____ to ____ and ____ ___
- cortex
- brainstem (corticobulbar tract)
- spinal cord (corticospinal tract)
lower motor neuron (LMN) is the _____ order neuron
2nd
LMN carries information in the ____ and ___ ___ that directly projects to the ____ in the periphery
- brainstem
- spinal cord
- muscles
T/F: lateral motor system controls movements of the limbs
True
Medial motor system controls what?
- posture
- balance
- axial control
what are the 2 corticospinal tracts?
- lateral corticospinal tract
- anterior corticospinal tract
corticobulbar are fibers projecting from ____ to nuclei in _____
- cortex
- brainstem
corticobulbar tract travels with the _____ tract in the cerebral ____ in the midbrain
- corticospinal
- peduncles
corticobulbar tract projects to motor nuceli of what cranial nerves?
- CN 5, 7, 9, 10, 11, 12
corticobuulbar tract controls LMN innverating muscles of the ___, ____, ____ and ____
- face
- tongue
- pharynx
- larynx
T/F: over 50% of cotricospinal tract fibers originate in the primary sensory cortex
False: over 50% of cotricospinal tract fibers originate in the primary MOTOR cortex
other tract fibers of the corticospinal tract originate from what 3 areas other then the primary motor cortex
- motor association cortex (premotor and supplmentary motor cortex),
- somatosensory cortex
- related association areas
describe corona radiata
- initial path of the corticospinal and cortocobulbar tracts
- travel from the cortical regions, axon fibers enter upper portion of cerebral white matter called corona radiata
describe internal capsule
- large fiber bundle carrying most of the axons running to and from the cerebral hemispheres
- corticospinal and corticobulbar tract pathway is from the corona radiata to the internal capsule
what are the 3 parts of the internal capsule
- anterior limb
- genu
- posterior limb
describe the pathway in which the corticobulbar tracts take from cortex to brainstem
cortical regions –> corona radiata –> internal capsule –> basis ppedunculi (in midbrain)–> brain stem cranial nerves (project onto associated CN)
the corticospinal and corticobulbar tracts enter the midbrain at the ___ portion of cerebral peduncles called the ____ ____
- ventral
- bassis peduculi
corticobulbar tract terminates on motor nuclei for CN on _____ side to control LMN
- opposite
describe the pathway in which the corticospinal tracts take from cortex to brainstem
cortical regions –> corona radiata –> internal capsule –> basis pedunculi (in midbrain)–> ventral pons–> medulla (which becomes the spinal cord)
T/F: the corticospinal trac form the pyramids at ventral medulla
true
the corticospinal tract axons cross to the opposite side at the ____-____ junction also called the ____ ____
- cervical-medullary junction
- pyramid decussation (great motor cross over)
corticospinal tract= ____ % cross over while ____% remain on ipsilateral course
- 85%
- 15%
corticospinal tract fibers that have crossed to controlateral side enter ____ colummns of spinal cord and form the ____ _____ tract
- lateral columns
- lateral cotricospinal tract
corticospinal fibbers that did not cross over course down the spinal cord on the ____ columns forming the _____ ______ tract
- anterior columns
- anterior corticospinal tract
functions of the lateral corticospinal tract (lateral motor system)
- controls movement of the extremities
functions of the anterior corticospinal tract (medial motor system)
- controls proximal axial and girdle muscles
for the lateral motor system: the pyramidal decussation allows clinicians a clue about location of lesion on corticospinal tract…. the right motor cortex directly commands movement on what side?
- left
for the lateral motor system: the pyramidal decussation allows clinicians a clue about location of lesion on corticospinal tract…. right side of body movements get controls by what side of the motor cortex?
- left
T/F: lesions above pyramidal decussion produce ipsilateral deficits in both upper and lower extremities
false: contralateral deficits
lateral corticospinal tract fibers controlling upper extremity are ___ to those controlling lower extermity
- medial
T/F: lesions below medulla produce ipsilateral deficits below level of lesion
true
LMB terminate at motor end plates of skeletal muscles of limb… known as _____ _____
- neuromuscular junction
lateral corticospinal tract enter spinal cord and terminate on what 2 areas?
- interneurons (modulatory function)
- ventral horn cells of the lower motor neurons (anterior horn cells)
what are the functions of the lateral corticospinal tract?
- strongly influences muscles of the extremities; Especially distal muscles important for execution of fine, skilled movements
- tends to have a facilitative action upon anterior horn cells with motor neurons to flexor muscles
inhibitory influence on anterior horn cells of motor neurons to extensor muscles - tends to have a facilitative action upon gamma motor neurons
- Also projects on sensory neurons in the dorsal horn and control the amount of information to be sent to the CNS
what is the most common lession for corticospinal tract and examples. what are the other causes?
- vascular
- typically middle cerebral artery or vertebrobasilar artery
- other causes: tumor, trauma, demylinating diseases
what do we typicall find when lesions of the lateral corticospinal tract occur
- hypertonia (increased muscle tone): increased resistance to passive stretch
- increased velocity-dependent muscle response (spasticity)
- increased deep tendon reflexes (hyperreflexia)
- Babinski’s sign- positive
- Clonus- positive
- muscle weakness
what is the function of the anterior corticospinal tract
- Critical to control of bilateral axial muscles and muscles of shoulder and pelvic girdles
T/F: the anterior corticospinal tract first project on the interneurons which in turn project on anterior horn cells
true
upper motor neurons contributing to lateral corticospinal tract originate predominantly in _____ _____ cortex
- primary motor cortex
upper motor neurons contributing to anterior corticospinal tract originate mainly in _____ _____ cortex
- motor association cortex
T/F: unilateral lesions of the medial motor system cause deficits on ipsilateral side
False: Since medial motor systems terminate on interneurons that project to both sides of spinal cord unilateral lesions of medial motor systems do not produce obvious deficits
