Organization of motor pathways Flashcards
Overview of the motor organization
signal originates in the prefrontal cortex, goes to the premotor cortex and then finally reaches the Primary motor cortex. Motor signals from here are coarse and require modulation by the basal ganglia, cerebellum and sensory systems.
Rubrospinal tract and reticulospinal tracts connection with main pathways
Primary motor cortex sends message to red nucleus and then to the spinal cord
Reticulo spinal system receives input from ALS and the primary motor cortex and sends it to the muscles.
Vestibulospinal tract
Vestibulospinal tract receives sensory from vestibular nuclei but are influenced weakly by the cerebral cortex and are largely involuntary. They also receive feedback from muscle spindles, DCML pathways, ALS pathways,
Lower motor neurons
transmit signals from teh central nervous system directly to muscle cells.
Upper motor neurons
originate in brain and regulate lower motor neurons
undergo decussation to exert either bilateral or contralateral control
Pontine and Medullary reticulo spinal pathway
Pontine- oral and caudal reticular nuclei in pons
Medullary- Gigantocellular reticular nucleus in medulla
Lateral and Medial Vestibulo spinal
lateral- lateral vestibular nucleus(largely pontine)
Medial- medial vestibular nucleus in pons and medulla
the descending motor tracts are subdivided into
ventromedialpathways(BIAS for EXTENSION)- pontine reticulospinal, lateral vestibulospinal, medial vestibulospinal
lateral pathways(BIAS for FLEXION)- Lateral corticospinal, rubrospinal, medullary reticulospinal
Rubrospinal tract
Red nucleus (midbrain)
corticobulbar
pyramidal cells Layer 5 of brodmann’s area 4
Lateral Corticospinal
Pyramidal cells in layer 5 of broadmann’s area 4
Lateral pathway images
Medial pathways image
in the ventral horn of the spina cord, flexor and adductor neurons lie
dorsal to the extensor and abductor neurons
Cells for distal muscles lie
laterally to those for truncal structures
Location of motor neuorns, flexor biased white matter and extensor biased white matter
lateral motor pathways strongly influence
Flexor muscles whose spinal motor neurons dewll in the distal portion of the ventral horn
medial motor pathways more strongly influence
extensory muscles with spinal motor neurons that dwell in the ventral portion of the ventral horn.
Amyotropic Lateral Sclerosis (Lou Gehrig’s disease)
initially destroys lower motor neurons and eventually parts of the corticospinal/bulbar tracts and the primary motor cortex (precentral gyrus and anterior paracentral lobule
symptoms-
- weakness or difficulty swallowing
- require ventilation and gastrostomy
- atrophy
- fasciculations
- spasms,
- cramping,
- loss of thenar, hypothenar, interossei, arm and sholder muscles
- reduction of cough reflex- leads to pneumonia
- bulbar motor nuclei deficits- difficulty swallowing, coughing, speaking
- weak pharyngeal and laryngeal muscles
- death occurs from respiratory insufficiency and aspiration pneumonia
Anterior Spinal Artery Syndrome
Anterior spinal aretery supplies two thirds of the spinal cord.
lesions of- anterior horn cells, lateral and anterior corticospinal tract, anterolateral system
Symptoms
- spastic paraparesis
- bilateral extensor plantar response
- bilateral loss of pain and temperature below lesion
- touch vibration, propriocepion intact
- retention of urine
- sexual functions impaired.
central medullary synrome
syringomyelia is a longitudinal cysts that develops along the central canal. it usually expands ventrally to compress the ventral horn and ventral white commissure
usual symptoms
- muscular atrophy(hand most often due to cervical involvement)
- loss of pain and temperature at the level of the lesion.
- can also be caused by tumors or hemorrhages.
- may produce pain and weakness with stiffness in the back, shoulders, arms, and legs.
- can also disturb sweating, sexual functions, bladder, and bowel controls.
