Comprehensive Study Guide to the Motor System and Movement Disorders (copy)

Hierarchical Organization of the Motor System

A system proposed by Hughlings Jackson, characterized by a descending order from more sophisticated to less sophisticated functions.

Direct Pathways

Motor pathways that involve pyramidal tracts, originating from the cerebral cortex.

Extrapyramidal Pathways

Indirect motor pathways that do not pass through the medullary pyramids, including tracts like rubrospinal and vestibulospinal.

Premotor Area (PMA)

Brain region involved in postural fixation; receives input from the prefrontal cortex and parietal lobe.

Supplementary Motor Area (SMA)

Area responsible for motor planning and responding to internal cues.

Upper Motor Neurons (UMNs)

Neurons located entirely within the CNS, originating in the cortex and forming descending tracts.

Lower Motor Neurons (LMNs)

Neurons located in the spinal ventral horns or brainstem; final common pathway to skeletal muscles.

Corticospinal Tract

A direct activation pathway allowing for fine motor control, divided into lateral and anterior corticospinal tracts.

Corticobulbar Tract

Innervates the head and face; involved in cranial nerve motility.

Rubrospinal Tract

Originates from the red nucleus, influences distal limb movements.

Vestibulospinal Tract

Maintains balance by being excitatory to extensors in response to head movement.

Basal Ganglia

Brain nuclei that influence motor activity through direct and indirect pathways.

Parkinson's Disease (PD)

A movement disorder characterized by loss of dopaminergic neurons leading to motor symptoms like rigidity and bradykinesia.

Huntington's Disease (HD)

Characterized by neuronal death in the striatum, leading to excessive cortical excitation and chorea.

Upper Motor Neuron (UMN) Lesion

Results in paralysis of movements, increased tone, and hyperreflexia.

Lower Motor Neuron (LMN) Lesion

Affects individual muscles, resulting in decreased tone and pronounced atrophy.

Tremor

A rhythmic, oscillatory movement of body parts.

Ataxia

Breakdown of coordinated execution, leading to unsteadiness and wide-based gait.

Dystonia

Twisting, repetitive movements that result in abnormal static postures.

Myoclonus

Sudden, shock-like contractions or inhibitions.

Hemiplegia

Paralysis of half the body.

Dysmetria

The inability to judge distance, often associated with ataxia.