Exam2Lec9CerebellumVOR Flashcards
What does the vestibular portion of the inner ear detect?
Movements
the cochlear portion detects sound
In humans the vestibular system has evolved to provide?
- Orientation
- Equilibrium
The vestibular system is responsible for sensing head motion via what two mechanisms?
- By maintaining postural control
- By stabalizing images on the fovea of the retina ( gaze)
The vestibular system transmits info to the central vestibular pathways to control what?
Reflexes and perceptions
the vestibular system is part of a complex mutisensory system- it never stands alone, works w/ other system
The peripheral vesitibular is a membranous labyrinth within where?
The temporal bone
What are the 5 neural structures of the peripheral vestibular and what do they respond to?
- 3 semicircular canals: respond to ANGULAR acceleration
- 2 otolith organs: respond to LINEAR acceleration, tilt, and gravity
the SSC are positioned in the orthogonal planes
What are the 2 otolith organs and they sense motion in what planes
?
- Utricle: senses motion in the HORIZONTAL plane (foward-back and left-right)
- Saccule: senses motion in the VERTICAL plane (up-down) and gravity
they work together
utricle: braking in a car
saccule: going up or down in an elevator
5 structures that each otolith organ contains:
- Macula
- Hair cells
- Gelatinous substance
- Otoconoia (calcium carbonate crystals) hy
- Afferent nerve fibers
When the head moves, the otolith-gel mass (otoconia) drags on the hair cells causing what?
An excitatory or inhibitory response
The semicircular canal responds to what and where are the 3 canals positiones?
Responds to angular acceleration and are positioned in the orthogonal planes.
each canal is sensitive to movement in its own plane
together, the 3 canals can code the directionand amplitude of any head roation
One end of each semicircular canal is enlarged to form the sensory receptor called the
ampulla
What are the semicircular canals filled with?
endolymph
What are the 3 structures within the ampula of the SCC?
- Cupular (gelantinous mass): separates the SCC from vestibule
- Crista w/ hair cells: kinocilium (long stereocilia), 50-100 stereocilia
- Vestibular afferents
tonotopically organized
During ____ the endolymph inside the SCC lags behind movement of the SCC due to inertia and pulls on the cupular which deflects the stereocilia
rotational acceleration
SCC are “coplanar mates” Explain this concept
Associated with respective SCC on opposite side. (Left Horizontal paired with Right Horizontal)
How do the SCCs work to respond to a given rotational head movement?
Pairs of SCC on opposite sides of the head respond in opposite ways to a given rotational head movement (excitatory for one, inhibitory for the other).
Disagreement between corresppnding SCCs on the two sides of the head causes what?
- Vertigo
- Nausea
What are the two branches of CNVIII
Vestibular nerve + Cochlear nerve
Primary vestibular neurons are biopolar neurons whose cell bodies form ____ in the internal auditory canal
Scarpa’s Ganglion
What are the 2 branches of the scarpa’s ganglia?
- Superior vestibular nerve
- Inferior vestibular nerve
What does the Superior vestibular nerve innervate?
- horizontal canal
- anterior (superior) canal
- Utricle
“sUp”=U for utricle
What does the Inferior vestibular nerve innervate?
- Posterior canal
- Saccule
Most vestibular nerve fibers terminate where?
in the ipsilateral vestibular nucleus on the floor of the 4th ventricle
Some vestibular nerve fibers (mediating postural control) terminate where?
directly on the cerebellum
Contributes to body movement, coordination & posture during static & dynamic activities
Discriminate between movement of self & movement of the environment
What is the ascending pathway of the vestibular nerve tract?
Medial longitudinal fasciculus (MLF)
What is the descending pathway of the vestibular nerve tract?
Lateral vestibulospinal tract
Medial Vestibulospinal tract
What are the 3 classic vestibular reflex arcs and what are they responsible for?
- Vestibulospinal Reflex (VSR): Responsible for keeping you upright
- Vestibulocolic Reflex (VCR): Responsible for keeping your head upright/in a horizontal plane (to protect brain)
3. Vestibular-Ocular Reflex (VOR): Responsible for keeping gaze
- trip and catch your self example
What is the VOR responible for?
allows the eyes to be stable during head movements (gaze control).
The Peripheral vestibular neurons that innervate the SCCs are connected to what to what structues do the VOR?
3 pairs of Muscles controlling the eyes
* Medial and lateral rectus
* Superior and inf rectus
* inf and sup oblique
The ears can tell eyes to move in diff directions and work together. One pair of muscle can be excited while the other is inhibited
Pathway of signals of the VOR
LY
- SCC
- Vestibular nerve
- Vestibular nucleus
- Ocular nucleus (depends on which muscle)
- Ocular muscle
VOR
If you turned your head to the left, what direction does your eye turn to maintain frontal gaze?
To the right
If you turned your head to the left
Which SCC is excited?
Causing what muscles of the eye to be CONTRACTED?
Excitation of L horizontal SCC causes contraction of
Left medial rectus and Right lateral rectus
If you turned your head to the left
Which SCC is inhibited?
Causing what muscles of the eye to be RELAXED?
Excitation of R horizontal SCC causes relaxation of
Right medial rectus and Left lateral rectus
The cerebellum influences movements primarily by modifying the activity patterns of what?
upper motor neurons.
What are the primary fxns of the cerebellum?
- To detect the difference - “motor error“ - between intended and actual movements
To reduce the error through its influence over upper motor neurons incorporating motor learning when the correction is stored
cerebellum is a multisensory system that is ADAPTIVE
note that it does sensory motor coordination INDIRECTLY, it sends info back to sensory systems to do the fxns mentioned
What are the 2 main gray matter structures of the cerebellum? LY
- Laminated cortex
- Clusters of cells in nuclei buried deep in the white matter
What are the 3 hemispheres of the cerebellum?
- Cerebrocereellum (lateral)
- Spinocerebellum (median and paramedian)
- Vestibulocerebellum (caudal and inf)
Cerebrocerebellum (lateral)
receives what kind of input?
what does it regulate?
- Receives indirect input from areas of cerebral cortex.
- Regulation of skilled movements
- Planning and execution of complex spatial and temporal sequences
Vestibulocerebellum (caudal and inf)
includes what structures?
what does it regulate?
- Includes the flocculus and nodulus
- Regulation of movements associated with posture and equilibrium/balance and Vestibular-Ocular Reflex (VOR)
Spinocerebellum (median and paramedian)
receives what kind of input?
what does it regulate?
- Receives direct input from spinal cord
- Paramedian part – movements of distal limbs
- Median part (along vermis) – movements of proximal muscles and eyes
What structure is responsible for the major INPUTS of the fiber bundles of cerebellum
Cerebellar peduncles
Sensory information can enter/leave the cerebellum by BOTH the cerebellar peduncles and deep cerebellar nuclei.
What structure is responsible for the major OUTPUTS of the cerebellum
Deep cerebellar nuclei
Sensory information can enter/leave the cerebellum by BOTH the cerebellar peduncles and deep cerebellar nuclei.
Major inputs to the cerebellum enter via ____ and ____ peduncles.
middle, inferior
not a direct pathway
input pathways that reach the cerebellum from other brain regions project to both the cerebellar cortex and deep nuclei
The output from the cerebellum comes mainly from what? What is the exception?
deep cerebellar nuclei.
The exception is that the inferior peduncle contains descending output (efferent) fibers from cerebellum
this is the cerebellum telling our body to make a correction
think of the deep cerebellar nuclei as an intermediate before reaching the target organ
input/output summary table
Cerebellar cortex: Cerebrocerebellum
Cerebellar peduncles(major input)?
Deep cerebellar nuclei (major output)?
Cerebellar peduncles(major input): sup and middle peduncle
Deep cerebellar nuclei (major output): denate nucleus
input/output summary table
Cerebellar cortex: Spinoocerebellum
Cerebellar peduncles(major input)?
Deep cerebellar nuclei (major output)?
Cerebellar peduncles(major input): inf peduncle
Deep cerebellar nuclei (major output): interposed nuclei
input/output summary table
Cerebellar cortex: Vestibulocerebellum
Cerebellar peduncles(major input)?
Deep cerebellar nuclei (major output)?
Cerebellar peduncles(major input): inf peduncle
Deep cerebellar nuclei (major output): fastigial nucleus
What are the 3 layers of the cerebellar cortex?
- Molecular (dendrites and axons)
- Purkinje: output cells of the cerebellar cortex to deep cerebellar nuclei)
- Granule
Destination of the afferent pathways to the cerebellar cortex is to where?
Purkinje cells
all afferent n. fibers will lands on purkinje cell
What do purkinke cells of the cerebellar cortex do?
- Inhibit the excitatory neurons of the deep cerebellar nuclei
Sensory information enters the cerebellum via the cerebellar peduncles. From there, input information synapses at the purkinje cells of the cerebellar hemispheres. They then send inhibitory signaling to the deep cerebellar nuclei (main output centers).
Cerebellar Dysfunction
Definition of
A. Nystagmus
B. Dysmetria
C. Dysdiadochokinesia
Nystagmus – oscillatory instability of ocular fixation
Dysmetria – inaccurate movements that are too large or small (over and under reaching)
Dysdiadochokinesia – difficulty with rapid alternating movements
Cerebellar Dysfunction
Definition of
A. Asynergia
B. Tremor
C. Errors of Gait
Asynergia – decomposition of movement (strategy to compensate for dysmetria)
Tremor – during intended movement or at intentionally held position
Errors of gait – unsteadiness
