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60 Cards in this Set

  • Front
  • Back
How does the Lateral Vestibulospinal tract (LVST) function?
By receiving sensory input from CN 8 and using it to maintain balance and posture.
What are the 4 vestibular nuclei and where are they located?
-Superior, Inferior
-Medial, Lateral
Found in pons and medulla
Where does CN VIII get its input from?
The utricle, saccule, and semicircular canals.
What does CN VIII project to?
The vestibular nuclei
What gives input to the vestibular nuclei OTHER than CN VIII?
The flocculonodular lobes of the cerebellum.
Where the LVST originate?
In the lateral vestibular nucleus
Where does the LVST project?
Ipsilaterally to laminae VII and VIII in ALL SPINAL CORD LEVELS
What does the LVST do after projecting do the spinal cord?
Excites alpha and gamma LMNs of extensor muscles in the neck and limbs - so you sit up nice and straight!
What will a lesion to the vestibular nerve or nucleus result in?
Stumbling and/or falling toward the same side of the lesion.

You'll collapse like one of those little elastic dolls.
What absolutely doesn't happen in the LVST?
No crossovers!
2 functions of the Medial VEstibulospinal Tract (MVST):
1. Coordinates eye movements with each other
2. Vestibular ocular reflex
What IS the vestibular ocular reflex?
Coordination of eye movements to compensate for head movements.
Where does the LATERAL VST originate?
In the LATERAL vestibular nucleus
Where does the MEDIAL VST originate?
& INFERIOR vestibular nuclei.
To where does the MVST project?
1. Superiorly in MLF to CN III, IV, and VI nuclei
2. Inferiorly in MLF to SC Laminae VII and VIII; ONLY at cervical levels.
How does the MVST get to the spinal cord?
By projecting bilaterally within the medial longitudinal fasciculus (MLF).
What does the MVST do at the spinal cord levels?
Inhibits alpha and gamma LMNs controlling neck and axial muscles.
Does the MVST only project DOWN the MLF?
No; it also projects superiorly
Where does the MVST that projects superiorly within the MLF go to?
CN nuclei III IV and VI (for eye muscles)
What happens if you damage the peripheral oculomotor nerve III?
Unopposed Lateral rectus (CN VI) and so lateral strabismus.
What happens if you damage the periphal abducent nerve VI?
Unopposed Medial rectus (CN III) and so medial strabismus.
What happens if you damage the Abducens NUCLEUS?
Deficits in both CN III and VI because they're interconnected, so inability to look to the side in either eye- one can't abduct and one can't adduct.
What does INO stand for?
Internuclear Ophthalmoplegia
What is INO?
A lesion of the MLF
What is the problem in INO?
On attempted horizontal gaze, the eye on the side of the lesion can't fully adduct, and the opposite eye has nystagmus.
Explain what causes the problem in INO:
Interruption of the signal between the CN VI nucleus (the horizontal gaze center) and contralateral occulomotor nucleus interrupts input to the medial rectus muscle.
4 common causes of INO:
-Multiple sclerosis
-Pontine infarcts
What is the "Vestibular Ocular Reflex"?
The normal conjugate eye movements that are equal and opposite in response to head movements.
Who do you check for the presence of the vestibular ocular reflex?
Comatose patients
What would you expect to see if the vestibular ocular reflex was not intact due to MLF damage?
Eye movements in the SAME direction as head movements.
What are the 2 functions of the Corticotectal and Tectospinal Tracts?
1. Inferior fibers facilitate reflexive turning movements of head for the eyes
2. Superior fibers facilitate upward gaze
Where does the Corticotectal tract extend from (3 sites)and to?
From Visual cortex, Retina, and Inferior Parietal lobes TO the superior colliculus
Where do the Corticotectal tract fibers project from the Superior Colliculus to?
To Pontine Paramedian Reticular Formation, then via MLF to nuclei controlling extraocular muscles that facilitate upward gaze.
Where do Tectospinal fibers decussate?
In the dorsal tegmentum
Where do Tectospinal fibers go after they decussate in the dorsal tegmentum?
Anterior to the MLF to descend to the cervical spinal cord to nuclei like CN XI and laminae 6, 7, and 8 to turn the head up.
What is Parinaud's syndrome?
A lesion in the region of the superior colliculi or posterior commisure that leads to eye abnormalities.
Symptoms of Parinaud's syndrome:
-Impaired upward gaze
-Large irregular pupils that don't constrict w/ light but do with accommodation)
-Eyelid abnormalities (ptosis)
-Convergence-retraction nystagmus
What is convergence retraction nystagmus?
On attempting to gaze up, the eyes oscillate between convergence and retraction.
What are 2 causes of Parinaud's syndrome?
-Pineal gland tumors
2 Functions of the Reticulospinal tracts:
1. Posture
2. Autonomic
How does the reticulospinal tract control Posture? (2 ways)
By influencing both voluntary and reflexive movements by
1. Inhibiting (lat medullary) or 2. Exciting (med pontine) motorneurons innervating axial musculature.
What is the Reticular Formation?
A scattered group of neuron cell bodies and fibers that extend throughout the brainstem.
What gives input to the reticular formation?
Widespread areas throughout the cerebral cortex.
Where do fibers in the Lateral Reticulospinal Tract originate?
In the medial part of the medullary reticular formation, dorsal to the inferior olivary complex.
Where do descending fibers in the Lateral Reticulospinal Tract project?
To the lateral white columns on both the same and opposite sides to laminae 7, 8, and 9 of all spinal cord levels.
Where do ascending fibers in the Lateral Reticulospinal Tract project? What do they do?
To intralaminar and thalamic nuclei.
-Play a role in arousal and sleep.
How does the LRST affect spinal and cranial nerve motor neurons?
It inhibits them.
Where does the Medial Reticulospinal tract originate?
In the Pons
Where do fibers of the Medial Reticulospinal tract project?
They descend ONLY UNCROSSED through the anterior funiculus to laminae 7 and 8 of all spinal cord levels.
How does the MRST affect spinal motor neurons?
It excites them
What muscles are affected by the MRST? What is accomplished?
-axial muscles
-leg extensors
-Maintains posture
What is Decerebrate Posturing?
Increased muscle tone and extension of the upper and lower limbs with arms fully adducted and medially rotated, arched back, feet extended, toes curled.
What causes decerebrate posturing?
Damage to the inhibitory LRST, but remaining intact MRST facilitates extensor motor neurons.
How would you cause decerebrate posturing in a cat?
By transecting the brain between the superior and inferior colliculi.
What is a clinical scenario in which Decerebrate posturing could result?
In brainstem lesions caudal to the red nucleus.
What is the cause of lateral medullary syndrome of wallenberg?
A clot in PICA or the vertebral artery
What will be damaged on the side of the lesion in lateral medullary syndrome?
-Nucleus ambiguus - dysphagia, dysarthria, dim gag reflex.
-Spinal tract of V; lose pain and temp and touch from face
-Vestibular nuclei - have vertigo, nausea, vomiting, and nystagmus.
-Descending Symp fibers - get Horner's syndrome
What deficits will occur on the side opposite to the lesion causing lateral medullary syndrome?
Loss of pain and temp
Nucleus ambiguus is what CNs?
9 and 10
What is LOCKED IN syndrome?
Complete paralysis of all voluntary muscles in the body.