Vestibular System And Cerebellum Flashcards
What are the fx of the cerebellum?
The surface contains deep _____ with smaller creases made up of cortical ridges called ____.
Prominent fissures divide the cerebellum into ____.
Motor and controls the maintenance of equilibrium, influences posture, and muscle tone, and coordinates movement (operates at an unconscious level)
Fissures; folia
Lobes and lobules
The two hemispheres of the cerebellum are joined together by the ____.
Deep ____ separates small anterior lobes from larger ____.
_____ defines flocculus and vermis (the nodule), together form the _____.
Vermis
Primary fissures; posterior lobe
Posterolateral fissure; flocculonodular lobe
The inferior cerebellar peduncle sends ____ info to the cerebellum from the SC and brainstem.
It has what two parts?
Afferent
Juxtarestiform body (wall of 4th ventricle): composed of reciprocal fibers between the cerebellum and vestibular structures
Restiform body: contains fibers arising in the SC or medulla
Middle cerebellar peduncle is located ____.
It sends ____ info to the cerebellum from the contralateral pontine nuclei.
Superior cerebellar peduncle sends ____ fibers from the cerebellar nuclei and distributes them to the ____.
Laterally from the basal pons
Afferent
Efferent; diencephalon and brainstem
____ are gray matter that receive afferents from multiple regions and are the output/efferents of the cerebellum.
What are the nuclei?
Deep cerebellar nuclei
Dentate nuclues
Interposed nucleus: emboliform nucleus and globose nucleus
Fastigial nucleus
The folium of the cerebellum contains a _____ and a core of myelinated fibers (white matter) called ____.
The cerebellar cortex consists of what three cell layers (superficial to deep)? Location?
Cerebellar cortex; arbor vitae
Molecular layer: outer pale layer with few cells but high number of processes
Purkinje cell layer: between the granular layer and the molecular layer
Granular cell layer: inner region adjacent to the white matter core
Pukinje cells only contain _____ neurons of the cerebellum.
Granule cells contain ____ neurons that synapse with the _____ and the molecular layer (basket and stellate cells); they extend ____ fibers.
Golgi cells are _____ cells in the ____ layer, and extend dendrites into the molecular layer.
Basket and stellate cells are ____ cells in the _____ layer.
Efferent
Excitatory; purkinje cells; parallel
Inhibitory; granular
Inhibitory; molecular
Mossy fibers are cerebellar ____ axons that originate from the cerebellar nuclei and other nuclei in the SC, medulla, pons.
They branch profusely in the ___ layer, contact other cells, and create a ____.
The mossy fiber contains a central element called a _____; gives the mossy appearance and allow for _____.
Mossy fibers are excitatory to ____ and _____ cells.
Afferent
Granular layer; mossy fiber rosette
Cerebellar glomerulus; multiple inputs onto the fiber
Granule cell and golgi cell dendrites
Climbing fibers arise from the _____.
Climbing fibers are _____ fibers and send collaterals to the appropriate cerebellar nucleus that corresponds to the overlying cortical zone (fx).
They terminate in the ____ and wrap around purkinje dendrites.
Each purkinje cell is innervated by a single climbing fiber. They excite the ____ and ____ on which their collaterals terminate.
Inferior olivary nuclei
Olivocerebellar
Molecular layer
Pukinje cell and cerebellar nuclear neurons
Multilayered (monoaminergic) fibers come from what?
What is their pathway into the cerebellum?
Fx?
Locus ceruleus (noradrenergic), raphe nuclei (serotoninergic), and hypothalamus
Enter the cerebellum via the cerebellar peduncles -> send collaterals to the cerebellar nuclei -> axons terminate in the molecular and granular layers
Decrease the pukinje cell response rate
What are the three functional parts of the cerebellum?
Pontocerebellum
Vestibulocerebellum
Spinocerebellum
Pontocerebellum comprises the majority of the cerebellar hemisphere and ____. Fx?
Vestibulocerebellum is equated to the _____ lobe and _____ nuclei. Fx?
Spinocrerebellum approximates to the vermis with the ____ and _____ nuclei. Fx?
Dentate nuclei; muscle coordination, speed/force/trajectory of movements
Flocculonodular lobe and fastigial nuclei; maintenance of balance/EQ
Globose and emboliform nuclei; muscle tone/posture
Vestibulocerebellum is concerned with ____.
It has connections with the vestibular and reticular nuclei of the brainstem via the _____; they are relayed to the _____ flocculonodular lobe.
What is the pathway?
LMN output is bilateral via the ____ and _____ projections.
Maintenance of balance
Cerebellar peduncles; ipsilateral
Cortical efferent fibers -> fastigial nucleus -> vestibular nuclei and reticular formation
Vestibulospinal and reticulospinal
Spinocerebellum influences ____.
It contains afferents from the ____ and _____ tracts and receive input from muscle, joint, and cutaneous receptors via the _____.
Fibers terminate in the cortex of the ____ and ____.
Output is focused on what?
Fastigial efferents go to ____ muscles and globose and emboliform nuclei go to ____ muscles through the red nucleus and thalamus
Muscle tone and posture
Spinocerebellar and cuneocerebellar tract; inferior and superior cerebellar peduncles
Ipsilateral vermis and adjacent paravermis
The control of axial and limb musculature
Axial;limb
What is the fx of the pontocerebellum?
What are their principal afferent fibers?
Output is directed where?
Muscular coordination, trajectory, speed, and force of movements
Pontocerebellar fibers: cross to the opposite side of the brainstem, enter via the middle cerebral peduncle, terminate in lateral parts of the cerebellar hemisphere
Dentate nucleus: projects to the contralateral red nucleus and ventral lateral nucleus of the thalamus (via the superior cerebellar peduncle) -> has action on the cerebral cortical areas that give raise to descending corticospinal and Corticobulbar paths
What is dyssunergia?
Caused by lateral cerebellar lesion; deterioration of coordinated movement, decreased muscle tone (hypotonia), DTR, ataxia, unsteady gait (lean towards side of lesion)
What is dysmetria?
Caused by a cerebellar lesion and prevents pts from pointing to a moving or stationary object (point past the object=hypermetria; fall short of the object=hypometria)
What is a tremor?
What are the types?
Caused by a lateral cerebellar lesion
Kinetic tremor (intention tremor): pt performs a voluntary movement and is most obvious as the target is approached
Parkinson’s has resting tremor
Static tremor: pt stand with the UE extended (muscles contracted against gravity)
What are two vestibular receptor organs? Fx?
What are they innervated by?
Semicircular canals: rotational head movements (angular accelerations)
Otolith organs (utricle and saccule): translational head movements (linear accelerations)
Primary afferent fibers of the vestibular ganglion (Scarpa ganglion)
Central processes of these bipolar cells enter the brainstem and terminate in the ipsilateral vestiblular nuclei and cerebellum
What is the fx and targets of the vestibular nuclei?
What are the four vestibular nuclei and their location?
Process positional and movement info for control of visual and postural reflexes
Target oculomotor nuclei, vestibulocerebellum, contralateral vestibular nuclei, SC, reticular formation and thalamus
Superior vestibular nucleus: superolaterally in the central pons, bordered by the restiform body and 4th ventricle
Medial vestibular nucleus: in lateral floor of the 4th ventricle
Lateral vestibular nucleus: lateral to the medial vestibular nucleus and contains large neurons
Inferior vestibular nucleus: lateral to the medial vestibular nucleus and extends through the medulla
Primary vestibular afferent fibers enter the brainstem at the ____. They traverse the restiform body and bifurcate into _____ branches.
Afferent fibers from the semicircular canals project to _____
Pontomedullary junction; ascending and descending
Superior and medial vestibular nuclei
Otolith organs project primarily to the _____ nuclei.
Saccule afferents project to neurons in the ____ and influence _____.
Lateral, medial, inferior, vestibular nuclei
Contralateral oculomotor nucleus; vertical eye movements
Vestibular nuclei can encode both the angular and linear components of head movements.
Superior and medial vestibular nuclei receive info from _____.
Lateral and inferior nuclei receive info from ____.
What is the fx of theses cells?
Otolith receptors and one semicircular canal pair
Several canal pairs and otolith receptors
Distribute info about direction and speed of the head, movement, and head position
The vestibuloocular network permits keeping a _____ on an object while the head is moving.
This works through stabilizing eye movements called ____.
This reflex is ____ because the movements are equal in magnitude and opposite in direction to the head movement perceived.
This reflex can be suppressed and goes in multiple directions, especially ____.
Fixed gaze
Vestibuloocular reflex
Compensatory
Horizontal
Primary afferents from the horizontal semicircular canals project to specific neurons in the _____ nuclei.
They send axons through the medial longitudinal fasciculus to the ____.
Then abducen motor neurons send excitatory impulses via CN VI to _____.
Abducens interneurons send excitatory impulses to the _____ which innervates ____.
Medial and lateral vestibular nuclei
Contralateral abducens nucleus
Ipsilateral lateral rectus m
Contralateral oculomotor nucleus; medial rectus m
A 2nd set of vestibular neurons sends ____ signals to the ipsilateral oculomotor nucleus (medial rectus m).
A 3rd set of vestibular neurons carry _____ signals to the ipsilateral abducens nucleus.
This allows the medial rectus to contract while the lateral rectus relaxes.
Excitatory
Inhibitory
With large head rotations, ______ are active.
The vestibuloocular reflex directs the eyes slowly in a direction ____ to the head motion, initiating the ____ phase.
The eye reaches a limit of how far it can turn and springs back rapidly to ____, them moves in the same direction as the head is the ____ phase.
Compensatory eye movements
Opposite; slow phase
Central position
Fast
Combination of the slow phase punctuated by the fast return phase creates ____.
The slow phase relies on connections from the vestibular nuclei to what three CN nuclei?
Nystagmus
CN III, IV, VI nuclei
Movement of endolymph that underlies nystagmus can be induced how?
What does warm water cause?
Endolymph movement in the same direction can be induced in the _____ ear by cool water.
Deficits are named for the direction the eyes are moving in the _____.
Caloric nystagmus: adding water into a pt’s ear
Causes a convection current of endolymph -> causes nystagmus to the L with both eyes
Contralateral
Fast phase
Caloric nystagmus is the movement of the ____ that underlies the nystagmus.
Nystagmus can be reproduced by instilling cool or warm warmer into an ear.
Warm water into the L ear causes a convection current of endolymph causing ____.
Endolymph movement in the same direction can be induced in the _____ ear by instilling cool water.
Endolymph
L nystagmus
Contralateral
The slow phase of the oculoclonic reflex is done by what nuclei?
The fast phase signal originates from the ____.
A lesion or a comatose pt with a depressed RF but an intact brainstem will have deviation of the eyes in the direction of the ____ phase but no fast phase causing doll’s eye movements (oculoclonic reflex)
CN III, IV, VI nuclei
Reticular formation
Slow
What are doll’s eye movements?
Deviation of the eye in the direction of the slow phase
Turning the head from side-to-side causes similar lateral eye movements (no fast phase)
The brainstem controls the rapid conjugate eye movements called ____.
They are controlled by the ____ that contain premotor neurons projecting to the extraocular motor nuclei called the _____.
Lesions in this area are called ____.
Saccades
Paramedian pontine reticular formation (PPRF)
Horizontal gaze center
Horizontal gaze palsies
The PPRF contain ____ and _____ burst neurons.
When gaze shifts to the right, EBNs activate ____, IBNs suppress _____.
If this is inhibited ____.
Excitatory (EBN) and inhibitory (IBN)
CN VI nucleus neurons on the R side
CN VI nucleus neurons on the L side
The relay of information is slow
Medial longitudinal fasciculus (MLF) carries info about ____.
It connects the CN III, IV, VI to integrate movements directed by the gaze centers like ___ and info about _____.
The direction the eyes should move
PPRF; head movement (CN III)
