Neurophysiology 5: Motor System (Lecture 79) Flashcards
What is the function of the cerebellum?
Coordinates timing and smooth movements
DOES NOT INITIATE MOVEMENT (instead it corrects errors)
The cerebellum in conjunction with the vestibular system helps maintain ______ _____. It also helps regulate muscle ________.
Vestibular system
Tone
What is the importance of cerebellar peduncles?
Path for cerebellar efferents and afferent
Cerebellar afferents coming from the spinal cord are what pathways/which info?
Spinocerebellar and spinocuneocerebellar pathways
Proprioceptive information and LMN
Cerebellar afferents coming from the cerebral cortex are what pathways/which info?
Corticopontocerebellar pathway
Motor plan
Cerebellar afferents coming from the brain stem are what pathways/which info?
Extrapyramidal action, eyes, ears
Brainstem UMN, tectum and vestibular nuclei
What is the function of the spinocerebellum? Where does it send info to?
Coordinated movement and posture
Sends info to brainstem UMN
What is the function of the pontocerebellum? Where does it send info?
Coordinated and properly timed skilled movement (limbs)
To motor cortex
What is the function of vestibulocerebellum? Where does it send info?
Coordinated balance and eye movement
To vestibular nuclei
Where are cerebellar efferents?
Deep cerebellar nuclei
Cerebellar efferents do NOT have _____ ______ path. Meaning it is unable to initiate ______ or directly impact muscle ______.
Descending spinal path
Movement
Strength
What is hypermetria?
Toy soldier walk
What is ataxia?
Spinal walk
What are signs of cerebellar dysfunction in spinocerebellar?
Hypermetria and ataxia
What are signs of cerebellar dysfunction in pontocerebellar?
Intention tremors
What are signs of cerebellar dysfunction in vestibulocerebellar?
Wide based stance
Where is the vestibular apparatus? What is the function? What receptor does it house?
Located in the inner ear
Sets body equilibrium or balance
Houses the receptor organs for detecting head position and movement
The vestibular apparatus stabilizes what and coordinates what?
Stabilizes position of the head and trunk
Coordinates eye movements
Where are the receptors found in the vestibular apparatus?
Three semicircular ducts
Vestibule
Which receptor if found in the three semicircular ducts? What does it sense?
Crista apmullaris
Sense angular acceleration
What are the receptors found in the vestibule? What do they sense?
Macula saccule and macula utricle
Sense static equilibrium/balance and linear acceleration
What is the 1st order neuron in the vestibular apparatus? What is the 2nd order neuron?
1st : vestibulocochlear nerve and vestibular ganglion
2nd: vestibular nuclei in medulla
Describe the structure of crista ampullaris
Bathed in endolymph (high in K)
Hair cells embedded in gelatinous cupola
Lag behind endolymph during movement
Sterocilia tip toward kinocilium to induce AP
How does the crista ampullaris induce AP
Stereocilia tip toward kinocilium to induce AP
Describe the structure of the macula saccule and macula utricle
Hair cells imbedded in gelatinous layer with otholiths
Otholiths (ear rocks) weigh down membrane and stimulate hair cells
What are the vestibular nuclei projections?
Vestibulospinal tract
Medial longitudinal fasciculus
Cerebellum
Emetic Center
How does the vestibulospinal tract function?
Ipsilateral ventral funiculus
Activates extensor and inhibits flexors
Where does the medial longitudinal fasciculus go to? What is the function?
Goes to CNS III IV VI which innervate extraocular muscles
Helps eye fix on target- ‘Gazes stabilization’
What are the two pathways from vestibular system to cerebellum?
Direct: primary vestibular axons to cerebellar flocculonodular lobe
Indirect: vestibular nuclei project to cerebellar flocculonodular lobe
What is the peripheral vestibular subdivision?
Receptors (hair cells), vestibular nerve (inner ear structure)
What is the central vestibular subdivision?
Brain stem and cerebellar vestibular structure
Classic sign of vestibular disease? Which side is the lesion on?
Head tilt
Head tilt is towards lesion (because ipsilateral effect)
Signs of vestibular disease
Nystagmus
Head Tilt
Leaning/Falling/
How can you decide which side the vestibular system is damaged on, just based on nystagmus?
Vestibular system damaged on slower side of eye movement
Describe cerebellar ataxia?
Not knowing where you are in space, exaggerated movements, wide base stance
Describe vestibular ataxia
Head tilt with ataxia, horizontal eye movements, balance issues, falling to one side
Describe spinal/ proprioceptive ataxia
Crossing over, feet tangled up, thoracic/pelvic limb moving at different paces
