Module E-01 Flashcards
Lower Motor neuron
Motor neurons that communicate directly with somatic
muscle.
Upper Motor neuron
– Motor neurons arising from motor centers in the brain
that communicate either directly with lower motor neurons or indirectly via local interneurons
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Plegia?
Paralysis.
Pariesis
Subparalytic muscle weakness
Hemipariesis
Paralysis on one side of the body
Pyramidal motor system aka
corticospinal tracts
Where do lower motor neurons arise from?
either the spinal cord (contributing to spinal nerves) or the brainstem (contributing to cranial nerves).
Rubrospinal tract starts from ___________
the red nucleus
Name 4 Voluntary Motor pathways
1) Corticospinal
2) Corticobulbar
3) Rubrospinal
4) the 2 Reticulospinal
______________ is an involuntary pathway receive sensory input from the vestibular nuclei
VetsibuloSpinal
The motor systems receive somatosensory feedback from
1) the dorsal column/medial lemniscal pathways,
2) the anterolateral system (ALS),
3) the somatosensory cortex
4) the spinoreticular tracts
What is the purpose of Decussation of the Upper motor neurons?
Allows many motor centers exert either bilateral or contralateral muscular control
What is Start point of Lateral corticospinal Tract?
Pyramidal cells (layer 5) of Brodmann’s area 4
What is Start point of Corticobulbar Tract?
Pyramidal cells (layer 5) of Brodmann’s area 4
What is Start point of Rubrospinal Tract?
Red nucleus (midbrain)
What is Start point of Lateral vestibulospinal Tract?
Lateral vestibular nucleus (largely pontine)
What is Start point of Medial vestibulospinal Tract?
Medial vestibular nucleus in pons & medulla
What is Start point of Pontine (medial) reticulospinal Tract?
Oral and caudal reticular nuclei in pons (Pontine reticular formation)
What is Start point of Medullary (lateral) reticulospinal Tract?
Gigantocellular reticular nucleus in medulla (Medullary reticular formation)
3 Pathways that end Ventromedial tracts
1) Pontine (medial) reticulospinal
2) Lateral vestibulospinal
3) Medial vestibulospinal
3 Pathways that end Lateral tracts
1) Lateral corticospinal
2) Rubrospinal
3) Medullary (lateral) reticulospinal
Flexor and adductor neurons lie _________ in the ventral horn
dorsal
Extensor and abductor neurons lie _________ in the ventral horn
Ventral
Neurons for distal muscles lie ________ to those for truncal structures (i.e., proximal muscles)
Lateral
Lateral pathways are biased for _______ of the limbs and their SPINAL neurons lie in the _________ of the ventral horn
flexion; dorsal portion
Medial (Ventromedial) Pathways are Biased for ________ of the Limbs and their SPINAL neurons lie in the _________ of the ventral horn
Extension; ventral portion
Disease that affects Lower Motor Neurons
ALS
ALS
Amyotrophic Lateral Sclerosis
What is ALS
a progressive neuromuscular disease that initially affects and later destroys lower motor neurons and eventually also parts of the corticospinal/corticobulbar tracts
and the primary motor area (precentral gyrus and anterior
paracentral lobule).
Symptoms of ALS
– atrophy, weakness, fasciculations, spasms, and cramping of affected muscles; 50% of cases begin in one or both hands
– loss of muscle bulk in thenar, hypothenar, interossei, arm
and shoulder
– reduction of cough reflex => risk of aspiration pneumonia
– involvement of bulbar motor nuclei => difficulty in swallowing, coughing, and speaking.
– weakness, atrophy, and fasciculations in tongue
– involvement of pharyngeal and laryngeal muscles
– death occurs from respiratory insufficiency and aspiration
pneumonia
What are Fasciculations?
random contraction of denervated muscle
Cause of Anterior Spinal Artery Syndrome
-Anterior spinal arterial infarction
-Less common causes include tumors and epidural spinal
abscesses
Where is the Anterior Spinal artery located?
the anterior median fissure
Symptoms of Anterior Spinal Artery Syndrome
– spastic paraparesis
– bilateral extensor plantar response
– bilateral loss of pain and temperature below lesion
– touch, vibration, proprioception intact
– retention of urine
– sexual functions impaired
Most common cause of Central Medullary Syndrome
Syringomyelia
other causes include tumors and hemorrhages
Cause of Syringomyelia
a longitudinal cyst that develops along the central canal. The cyst usually expands ventrally and compresses the ventral horns and the ventral white commissure
Which area does Syringomyelia most commonly occur?
Cervical cord
Symptoms of Syringomyelia
segmental muscular atrophy (most frequently, muscles of hand are affected due to cervical involvement) and also a loss of pain and temperature senses due to destruction of the anterior white commissure
