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Neuro Exam 2 > Vestibular System and Cerebellum > Flashcards

Vestibular System and Cerebellum Flashcards

1
Q

Primary function of cerebellum

A

Entirely (unconscious) motor function

Maintenance of equilibrium, posture, muscle tone, coordination

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2
Q

Cerebellum is characterized by presence of deep fissures. Prominent fissures divide the cerebellum into ____ and _____.

The deep primary fissure separates the small _____ lobe from the ______ lobe.

The posterolateral fissure defines the _____ and _____

A

Lobes; lobules

Anterior;posterior

Flocculus; vermis (nodule)

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3
Q

The flocculus of the cerebellum + nodule of vermis = __________ of cerebellum

A

Flocculonodular lobe

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4
Q

Structures on cerebellum that are smaller creases made up of cortical ridges

A

Folia

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5
Q

______ ______ = superifical cellular layer of each folium

A

Cerebellar cortex

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6
Q

Layers of cerebellar cortex

A

Purkinje cell layer (sandwiched between granular layer)

Granular cell layer (immediately adjacent to white matter core)

Molecular layer (few cells but high # of processes)

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7
Q

Which layer of the cerebellar cortex contains the only efferent neurons of the cerebellum?

A

Purkinje cell layer

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8
Q

The granular cell layer of the cerebellar cortex contains excitatory neurons that synapse with _____ cells as well as ____ and ____ cells of the molecular layer

This layer also contains _____ cells which are inhibitory cells that extend dendrites into the molecular layer

A

Purkinje; basket; stellate

Golgi

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9
Q

2 types of cells in molecular layer

A

Basket cells
Stellate cells

[inhibitory cells]

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10
Q

___ ____ = core of myelinated fibers in cerebellum

A

Arbor vitae

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11
Q

Cerebellum consists of 2 laterally located hemispheres joined in midline by _______

A

Vermis

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12
Q

3 cerebellar peduncles:

Superior cerebellar peduncle = predominantly ______ fibers from cerebellar nuclei

Middle cerebellar peduncle = emerges laterally from basal _____; composed of ______ fibers to cerebellum from contralateral pontine nuclei

Inferior cerebellar peduncle = _____ fibers to cerebellum from spinal cord and brainstem

A

Efferent

Pons; afferent

Afferent

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13
Q

Largest cerebellar peduncle

A

Middle

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14
Q

Superior cerebellar peduncle is predominently efferent fibers from cerebellar nuclei which distribute where?

A

Diencephalon

Brainstem

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15
Q

The inferior cerebellar peduncle is associated with the:

_____ ____ (wall of 4th ventricle): composed of reciprocal fibers b/w cerebellum and vestibular structures

______ _____: contains fibers arising in SC or medulla

A

Juxtarestiform body

Restiform body

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16
Q

______ receive afferents from multiple regions and are the output/efferents of the cerebellum

A

Deep cerebellar nuclei

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17
Q

What are the 3 deep cerebellar nuclei?

A

Dentate nucleus
Interposed nucleus (anterior emboliform + posterior globose)
Fastigial nucleus

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18
Q

3 types of afferent fibers to cerebellar cortex

A

Mossy fibers
Climbing fibers
Multilayered (monoaminergic fibers)

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19
Q

______ fibers are cerebellar afferent axons that originate from cerebellar nuclei and other nuclei in the SC, medulla, and pons

A

Mossy

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20
Q

Mossy fibers branch profusely in ______ layer and contact other cells at irregular intervals, creating the _________

A

Granular; mossy fiber rosette

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21
Q

Central element of mossy fibers, giving them their mossy appearance

A

Cerebellar glomerulus

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22
Q

Mossy fibers are excitatory to _____cell and ____ cell dendrites

A

Granule; golgi

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23
Q

Climbing fibers are afferent cerebellar fibers that arise from the _____ nuclei.

______ fibers send collaterals to appropriate cerebellar nucleus that corresponds to overlying cortical zone

Climbing fibers terminate in molecular layer by entwining up the dendritic trees of the ______ dendrites

A

Inferior olivary

Olivocerebellar

Purkinje

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24
Q

Each purkinje cell is innervated by a single _____ fiber and they excite purkinje cells and cerebellar nuclear neurons on which their collaterals terminate

A

Climbing

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25
Q

Multilayered (monoaminergic) fibers are cerebellar afferents associated with what 3 structures?

A 
Locus ceruleus (noradrenergic)
Raphe nuclei (serotoninergic)
Hypothalamus
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26
Q

Multilayered (monaminergic) fibers enter the cerebellum mainly via _____ _____ and may send collaterals to cerebellar nuclei.

Axons branch diffusely and terminate in ____ and ____ layers, influencing all major cell types.

They function in decreasing spontaneous discharge rates and altering responsiveness of ____ cells

A

Cerebellar peduncles

Molecular; granular

Purkinje

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27
Q

3 functional subdivisions of cerebellum

A

Spinocerebellum (paleocerebellum)
Vestibulocerebellum (archicerebellum) - oldest
Pontocerebellum (neocerebellum)

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28
Q

The spinocerebellum approximates to the ____ and surrounding area, with the _____ and ____ nuclei

A

Vermis; globose; emboliform

29
Q

Function of spinocerebellum

A

Muscle tone/posture

30
Q

Spinocerebellum controls muscle tone/posture via afferents from _____ and ______ tracts, with info from muscle, joint, and cutaneous receptors via ______ and _______ cerebellar peduncles

A

Spinocerebellar; cuneocerebellar; inferior; superior

31
Q

Spinocerebellum fibers terminate in cortex of ipsilateral _____ and adjacent ________

A

Vermis; paravermis

32
Q

Output of spinocerebellum is focused primarily on control of axial and limb musculature — what neural pathways are involved with each?

A

Axial: vermal cortex + fastigial efferents —> vestibular and reticular nuclei

Limbs: globose + emboliform nuclei —> superior cerebellar peduncle —> red nucleus + thalamus

33
Q

The vestibulocerebellum is equated with the _____ lobe and _____ nuclei

A

Flocculonodular; fastigial

34
Q

Function of vestibulocerebellum

A

Maintenance of balance/equilibrium

35
Q

Vestibulocerebellum controls balance and equilibrium maintenance via connections with _____ and _____ nuclei of brainstem via inferior cerebellar peduncle. This info is relayed to the ipsilateral _____ lobe

A

Vestibular; reticular; flocculonodular

36
Q

Cortical efferent fibers of the vestibulocerebellum —> _______ nucleus ——> _______ nuclei + reticular formation

LMN output is bilateral via _____ and _____ projections

A

Fastigial nucleus; vestibular

Vestibulospinal; reticulospinal

[note that a portion of fastigial efferents goes contralateral]

37
Q

The pontocerebellum makes up the majority of the cerebellar hemisphere and ____ nuclei

A

Dentate

38
Q

Function of pontocerebellum

A

Muscle coordination + speed/force/trajectory of movements

39
Q

Fibers of pontocerebellum are principle afferents that cross to the contralateral side of the brainstem and enter via ____ cerebellar peduncle

They then terminate predominantly in lateral parts of _____ _____

A

Middle

Cerebellar hemisphere

40
Q

Output from pontocerebellum is directed to the ____ nucleus. It projects to the contralateral ____ nucleus and ventral lateral nucleus of the ________ (via superior cerebellar peduncle). The VLN then projects to the motor cortex

A

Dentate; red; thalamus

41
Q

The action of the pontocerebellum on the cerebral cortical areas gives rise to descending _____ and _____ paths

A

Corticospinal; corticobulbar

42
Q

Results of lesions of lateral cerebellum

A

Dyssynergia (deterioration of coordinated movement)

May also see hypotonia and decreased DTRs

Extremity ataxia

Unsteady gait + tendency to lean toward side of lesion

43
Q

Other nonspecific results of cerebellar lesions

A

Dysmetria = past-pointing (hypermetria vs. hypometria)

Tremor = intention tremor, static tremor

44
Q

Difference between 2 primary vestibular receptor organs

A

Semicircular canals (horizontal, anterior, posterior) = detect rotational movements aka angular acceleration

Otolith organs (utricle, saccule) = detect translational movement aka linear acceleration

45
Q

Receptor cells in vestibular receptor organs are innervated by primary afferent fibers of ______ ganglion

Cell processes of these bipolar cells enter the brainstem and terminate in ipsilateral ________ nuclei and cerebellum

A

Vestibular (scarpa ganglion)

Vestibular

46
Q

4 main vestibular nuclei and their locations

A

Superior vestibular nucleus (superolateral in central pons)

Medial vestibular nucleus (lateral floor of 4th ventricle)

Lateral vestibular nucleus (lateral to medial vestibular nucleus)

Inferior vestibular nucleus (lateral to medial and inferior to lateral)

47
Q

The superior vestibular nucleus is bordered by the ____ body and ___ ventricle

A

Restiform; 4th

48
Q

Which vestibular nuclei contains large neurons known as Deiters cells?

A

Lateral vestibular nuclei

49
Q

Major targets of vestibular nuclei

A 
Oculomotor nuclei
Vestibulocerebellum
Contralateral vestibular nuclei
Spinal cord
Reticular formation
Thalamus
50
Q

Primary vestibular afferents enter brainstem at _____ junction and traverse the ____ body before bifurcating into asecnding and descending branches

A

Pontomedullary; restiform

51
Q

Afferent fibers from semicircular canals project to ___ and ______ vestibular nuclei

Minor inputs reach the ____and _____ vestibular nuclei

A

Superior; medial

Lateral; inferior

52
Q

Otolith organs project primary afferents to which vestibular nuclei?

A

Lateral
Medial
Inferior

53
Q

Saccular afferents project to neurons in the contralateral _____ nucleus which influences vertical eyemovements

A

Oculomotor

54
Q

Vestibular nuclei show directional selectivity for particular head movements due to:

____ and ____ vestibular nuclei receive info from otoliths and one semicircular canal pair

____ and _____ vestibular nuclei receive info from several canal pairs and otolith receptors

A

Superior; medial

Lateral; inferior

55
Q

What network permits keeping a fixed gaze on an object while head is moving?

A

Vestibuloocular network (vestibuloocular reflex)

56
Q

The vestibuloocular reflex is characterized by primary afferents from horizontal semicircular canals that project to specific neurons in the medial and lateral vestibular nuclei

Describe the path of these axons

A

Primary afferents send axons through MLF to contralateral abducens nucleus

Abducens motor neurons send excitatory impulses via CN VI to ipsilateral lateral rectus m.

Abducens interneurons send excitatory impulses to contralateral oculomotor nucleus

A 2nd set of vestibular neurons sends excitatory signals to ipsilateral oculomotornucleus and a 3rd set of vestibular neurons sends inhibitory signals to ipsilateral abducens nucleus

57
Q

Compensatory eye movements present with large head movements characterized by combination of slow phases punctuated by fast return phases

A

Nystagmus

58
Q

Describe slow and fast phases associated with development of nystagmus

A

Slow phase: vestibuloocular reflex directs eyes slowly in direction opposite head motion (relies on connections from vestibular nuclei to CN III, IV, and VI nuclei)

Fast phase: moving in same direction as that of the head

59
Q

Caloric nystagmus is the movement of endolymph that underlies nystagmus. This can be reproduced with water in the ear. How does response differ with warm vs. cool water?

A

Warm water — eyes go to ipsilateral side

Cool water — eyes go to contralateral side

60
Q

Oculoclonic (oculocephalic) reflex slow phase vs. fast phase

A

Slow phase: vestibular nuclei —> CN III, IV, and VI nuclei

Fast phase: signals that originate from the reticular formation

61
Q

Oculoclonic reflex in intact individual vs. lesioned/comatose patient with depressed RF function but intact brainstem

A

Intact: both eyes look toward hot/cold fluid

Lesioned: deviation of eyes in direction of slow phase of expected nystagmus

62
Q

What are dolls eye movements?

A

VOR that is normally suppressed when a conscious individual moves head and eyes to one side simultaneously to look at something

63
Q

Brainstem circuitry that controls rapid conjugate eye movements, subdivided into systems controlling horizontal and vertical components of eye movements

A

Saccades

64
Q

What brain area contains premotor neurons that project to extraocular motor nuclei

A

Pontine reticular formation/paramedian pontine reticular formation (PPRF)

65
Q

Result of lesions in horizontal gaze center

A

Horizontal gaze palsies

66
Q

PPRF cells that project to extraocular motor neurons include hwat 2 cell types that produce a burst of APs preceding the activity of motor neurons?

A

Excitatory burst neurons (EBNs)

Inhibitory burst neurons (IBNs)

67
Q

What brain area carries info about the direction that eyes should move, connecting CN III, IV, and VI to integrate movements directed by gaze centers like PPRF and info about head movement from CN VIII?

A

Medial longitudinal fasciculus

[this is an integral component of saccadic eye movements as well as vestibuloocular and optokinetic reflexes]

68
Q

Alcohol cerebellar degeneration

A

Chronic alcohol use —> atrophy of cortex of anterior lobe of cerebellum + pontocerebellum and dentate nucleus

Late stages: severe LE and trunk ataxia

May be seen in conjunction with Korsakoff’s syndrome

69
Q

Autosomal recessive inherited disease causing progressive nervous system damage with the initial symptom of poor coordination, eventually requiring the pt be wheelchair bound

A

Friedrich’s ataxia

[causes functional necrosis and demyelination of proprioceptive neurons in dorsal roots, posterior columns, medial lemniscus, spinocerebellar tracts, and corticospinal tracts as well as damage to purkinje cells, dentate nucleus, and superior cerebellar peduncle]

Neuro Exam 2 (21 decks)

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