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Med Neuro Block 3 > Cerebellum Structure, Circuitry, and Function > Flashcards

Cerebellum Structure, Circuitry, and Function Flashcards

1
Q

Where is the cerebellum located

A

posterior cranial fossa

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2
Q

cerebellum is subdivided into

A
  • the flocculonodular lobe
  • vermis (worm)
  • anterior lobe
  • posterior lobe
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3
Q

Describe what you see in a mid-saggital section of the cerebellum

A
  • you see the arbor vitae (tree of life)
  • it is located posterior to the brain stem and the 4th ventricle
  • vermis: lingual (next to the superior medullary velum) and nodule (next to the inferior medullary velum)
  • Primary fissure
  • horizontal Fissure
  • Vermis
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4
Q

What 3 pairs of arteries supply the cerebellum

A
  • superior cerebellar artery: from basilar artery
  • Anterior inferior cerebellar artery (AICA): from basilar artery
  • Posterior inferior cerebellar artery (PICA): from vertebral artery
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5
Q

What are the numerous leaf like convolutions called

A

Folium

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6
Q

Where is the anterior lobe

A

in front of the primary fissure

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7
Q

where is the posterior lobe

A

behind the primary fissure

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8
Q

Where is the cerebellar tonsils

A

the medial inferior part of the cerbellum, may herniate

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9
Q

Describe the flocculonodular lobe

A
  • there is one nodule that is part of the vermis
  • there are two lateral flocculi
  • it is separated form the posterior lobe y the posterolateral fissure
  • forms the vestibulocerebellum: control of equilibrium,, balance, and eye movements (mediates vestibulo-ocular reflex VOR)
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10
Q

Vermis

A
  • longitudinal subdivision
  • along the midline
  • part of the spinocerebellum
  • control axial and proximal limb movements
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11
Q

intermediate zone

A
  • part of the spinocerebellum

- control of distal limb movemets

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12
Q

Lateral zone

A
  • part of the cerebrocerebellum

- planing and initiating moves

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13
Q

List the 2 excitatory afferents of the cerebellar cortex

A
  1. Climbing Fibers

2. Mossy Fibers

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14
Q

Climbing Fibers

A
  • from contralateral inferior olivary nucleus

- Synapse with Purkinje cells

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15
Q

Mossy Fibers

A
  • from all other sources

- synapse with granule cells, which activate purkinje cells

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16
Q

List the 5 major neuronal types and whether they are excitatory or inhibitory

A
  • Purkinje cells: inhibitory
  • Granule cells: excitatory
  • Golgi cells: inhibitory
  • Basket cells: inhibitory
  • Stellate cells: inhibitory
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17
Q

What are the three layers of the internal structure of the cerebellar cortex

A
  • Molecular Layer
  • Purkinje cell layer
  • Granular layer
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18
Q

Molecular Layer

A
  • dendrites of purkinje cells
  • parallel fibers of granule cells (which excite the purkinje cells)
  • climbing fibers from ION (contralateral Inferior olivary nucleus)
  • stellate cells
  • basket cells
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19
Q

Purkinje Cell Layer

A

Purkinje cells

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20
Q

Granular Layer

A

Granule Cells
Golgi Cells
Mossy FIbers

21
Q

Deep Cerebellar Nuclei

A
  • major output neurons of the cerebellum
  • receive collaterals of climbing and mossy fibers to the cerebellas cortex
  • receive inhibitory input from the purkinje cells of the cerebellar cortex
  • the output from the deep cerebellar nuclei is excitatory
22
Q

is the output from the DCN excitatory or inhibitory

A

excitatory!!!!

23
Q

List the three nuclei of the Deep Cerebellar Nuclei

A
  1. Dentate nuclei
  2. Interposed Nuclei
  3. Fastigial nuclei
24
Q

Dentate nuclei

A
  • largest most lateral nuclei of the DCN

- receives projections from the lateral zone of the cerebellar hemispheres

25
Q

Interposed nuclei

A

(Emboliform + Globose)

-receive projection of the intermediate zone of the cerebellar hemispheres

26
Q

Fastigial Nucleus

A

most medial

-receive projections from the vermis and some input from the flocculonodular lobe

27
Q

Synaptic Circuit of the Climbing Fibers

A
  • Climbing fibers
  • excitatory to Purkinje cells
  • inhibitory to deep cerebellar nuclei
  • excitatory output to other brain regions
28
Q

Mossy fibers

A
  • excitatory to granule cells, which form parallel fibers
  • which send excitatory to Purkinje cells
  • inhibitory to deep cerebellar nuclei
  • excitatory output to outer brain regions
29
Q

Inhibitory interneurons

A
  • Basket and stellate cells in the molecular layer inhibit Purkinje cells
  • Golgi cells in the granular layer inhibit granule cells
  • these basic circuits are repeated numerous times
30
Q

What is the ratio/relationship of purkinje cells and climbing fibers

A

a climbing fiber can innervate (excitatory) to several Purkinje cells, but each purkinje cell is only innervated by one climbing fiber

31
Q

What makes up the Vestibulocerebellum

A
  • Flocculonodular Lobe

- Inferior Vermis

32
Q

Function of the Vestibulocerebellum

A
  • controls balance and equilibrium while standing or moving
  • controls eye movements
  • coordinated movements of the head and eyes
33
Q

List the afferent fibers to the vestibulocerebellum

A

-Vestibular labyrinth (ipsilateral
semicircular canals and maculae of the utricle and saccule)

-Vestibular nuclei in the medulla that
relay information from the vestibular labyrinth. The vestibulocerebellar fibers travel via the Juxtarestiform body. (meaning signal goes to vestibular nuclei and then vestibular nuclei sends signal to the vestibulocerebellum)

-Visual centers (LGN, superior
colliculus, and the visual cortex) via the pontine nuclei (meaning the signal comes from the visual centers to the pontine nuclei and then the pontine nuclei send the signals to the vestibulocerebellum)

34
Q

Efferent signals from the Vestibulocerebellus

A

to Vestibular nuclei in the medulla (reciprocal connections)

35
Q

What do the vestibular nuclei give rise to and what is the significance of that

A
  • Vestibulospinal tracts innervating LMNs of the axial muscles. Thus, the
    vestibulocerebellum is important for the control of axial muscles used in
    maintaining equilibrium and balance.

-Medial longitudinal fasciculus, which projects to the oculomotor, trochlear, and
abducens nuclei. Thus, the vestibulocerebellum is involved in coordinating
movements of the head and eyes.

36
Q

What makes up the Spinocerebellum

A

Vermis and Intermediate zone

37
Q

Functions of the Spinocerebellum

A
  • Vermis: control of axial and proximal limb and muscles
  • Intermediate zone: control of distal limb muscles
  • Both control ongoing execulation of movements
38
Q

Afferent inputs of the Spinocerebellum

A
  • Ipsilateral spinal cord and lower medulla: via the inferior cerebellar peduncle (Restiform body)
  • Dorsal spinocerebellar tract
  • cuneocerebellar tract

-Contralateral inferior olivary nucleus (ION) via the oliviocerebellar tract and the inferior cerebellar peduncle

-Ipsilateral spinal cord then crosses the midline and ascend via the contralateral Ventral
spinocerebellar tract then joins the contralateral Superior cerebellar peduncle
(Brachium conjunctivum) and then re-cross the midline and then ends in the Anterior lobe of the
ipsilateral Spinocerebellum

39
Q

Efferent outputs form the vermis

A

**-Via the Superior cerebellar peduncle (Branchium conjunctivum)

-The Vermis relays information about the neck and trunk to the Fastigial nucleus of
the Deep cerebellar nucleus (DCN).

-The Fastigial nucleus projects to the brain stem, which projects to the spinal cord
via the Medial descending system to innervate axial and proximal limb muscles.

-The Fastigial nucleus also projects to the Thalamus, which then projects to the
motor and premotor cortical areas that control voluntary movements.

40
Q

Efferent outputs from the intermediate zone

A

**via the superior cerebellar peduncle

-The Intermediate zone relays information about the limbs to the Interposed nuclei
of the DCN (Emboliform and Globose).

-The Interposed nuclei project to the brain stem (mainly the Red nucleus), which
projects to the spinal cord via the Lateral descending system to innervate distal
limb muscles.

-The Interposed nuclei also project to the Thalamus, which then projects to the
Motor and Premoter cortical areas that innervate the distal limb muscles via the
corticospinal tract.

41
Q

Cerebrcerebellum Functions

A

Lateral zone

involved in the initiation, planning and mental rehearsal of complex motor actions

42
Q

Afferent inputs to the cerebrocerebellum

A
  • Contralateral cortex via corticopontine tract
  • synapse with pontine nuclei
  • pontine nuclei project via the Middle Cerebellar Peduncle (Brachium pontis) that crosses the midline
  • projects to the Cerebrocerebellum. This is the Cortico-ponto-cerebellar tract, which is a crossed pathway.
43
Q

Efferents outputs from the cerebrocerebellum

A
  1. The Lateral zone projects to the Dentate
    nucleus of the DCN, which projects via the Superior cerebellar peduncle (Brachium conjunctivum) to the contralateral Red nucleus in the midbrain. The Red nucleus then projects to the thalamus. This constitutes the Dentato- rubro-thalamic tract.
  2. The thalamus projects to the Motor and
    Premotor cortical areas which send two different types of projections
    2a. Corticospinal tract: which crosses the midline
    at caudal medulla to innervate the spinal cord (i.e., back to the side ipsilateral to the original dentate nucleus).
    2b. Corticopontine tract: which innervates the
    pontine nuclei. These pontine nuclei then project via the Middle Cerebellare Peduncle to the contralateral Cerebrocerebellum (i.e., back to the side ipsilateral to the original Lateral zone of the cerebellar cortex.
44
Q

Why is the double crossing in the cerebrocerebellar pathways important

A

Double-crossing: The fact that the output of
the Cerebrocerebellum is a crossed pathway
and that it receives a contralateral input
means that cerebellar lesions would result in
ipsilateral symptoms.

45
Q

Monoaminergic afferent fibers from the brainstem

A
  • Serotoninergic fibers from the raphé nuclei
  • Noradrenergic fibers from the locus ceruleus
  • Both project to all parts of the cerebellum and play a modulatory role.
46
Q

General Function of the cerebellum

A

-Control of balance and eye movements (vestibulo-ocular reflex)

-Regulates movement and posture indirectly by modulating the output of the major
descending motor systems

-Compares intention with actual movement and compensates for errors in movement:

  • The function of the cerebellum is changed by experience; it is, therefore, involved in
    motor learning.
47
Q

How does the cerebellum compare intention with actual movement and compensate for errors in movement

A
  • The cerebellum receives information about plans for movement from motor and premotor cortex via the corticopontocerebellar tract.
  • The cerebellum monitors the integration of descending and peripheral information
    regarding movement in the spinal cord via the ventral spinocerebellar tract.
  • The cerebellum receives feedback information from the sensory periphery via the
    dorsal spinocerebellar tract during the course of the movement.
  • The cerebellum projects to motor centers that send fibers to the spinal cord: e.g., dentatorubrothalamic tract, thereby adjusting the output of the motor system.
48
Q

What are some dysfunction of the cerebellum

A
  • lesions cause disruption of coordinated limb and eye movement, impairs balance, and reduces muscle tone
  • cerebellar lesions typically cause ipsilateral motor signs
  • Major signs are ataxia, hypotonia, intentional tremor, dysdiadochokinesia (irregular pattern of alternating movements), dysmentria, nystagmus, and titubation
  • damage can impair motor learning

Med Neuro Block 3 (10 decks)

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