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Motor System - Coggle Diagram
Motor System
Lower Motor Neuron
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Neurons are recruited from weakest to strongest, all muscle fibers are the same fiber type
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Lesions
Signs
Decreased/Absent reflexes, normal/hypotonic tone, fasciculations, muslce atrophy
Reflexes
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Reciprocal Reflex
when one contracts, the other muscle relaxes
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Inverse Myotatic Reflex
Detect excess weight, inhibit flexions, and activate extensors
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2 Motor Neuron System
Upper Motor Neuron
Lesions
Hyper-reflexia, Spasticity, no muscle wasting, Muscles affect in groups, Upgoing toe
Lower Motor Neuron
Lesions
Hypo-reflexia, or areflexia, tone is normal/hypotonic, marked muscle atrophy, weakness pattern, downgoing or mute toe
Motor Cortex
Prefrontal, premotor interesting from physiologic P.O.V but rarely damaged
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Direct Pathway
Characteristics
CST, upper motor, from cortex to spinal
Goes through distinct tract (Midbrain, pons, medulla)
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Lesions
Hyper-reflexia, upgoing toe, spasticity, Weakness
Reflexes
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Clonus
Involuntary, rythmic, repetitive muscular contractions, reflection of hyper-reflexia
Spasticity
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Often unidirectional "Spastic catch," "clasp knife" phenomenon
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Pyramidal Weakness
Pattern of weakness: extensors, flexor in lower limbs, pronator drift
Babinski Sign
Upgoing toe, extensor plantar response
Localizing
Unilateral UMN lesion, likely opposite side
"Crossed Findings" - Limb weakness on opposite side of "cranial muscle" weakness, facial muscles in Pons, palate/tongue muscles
In spinal Cord: Rare, and causes ipsilateral issues
Modifying Circuits
Basal Ganglia
Functions, in motor control which is incompleltely understood, help plan and control complex patterns of movement
Striatum (caudate, putamen), Globus Pallidus (external and internal), Subthalamic nucleus, Substantia Nigra
Disorders
Hyperkinetic
Excessive movements, Neuropsychiatric symptoms
Hypokinetic
TRAP (Tremor, Rigidity, Akinesia, Postural Instability)
Rigidity
Extrapyramidal sign resulting in increased muscle tone, all directions of movement, often associated with tremor, Associated with bradykineasia, postural instability
Cerebellum
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Ipsilateral defects
Hypotonia, limb incoordination
Important Clinically
Apraxias, Upper motor neuron, Extrapyramidal, cerebellar, lower motor neuron