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Flashcards in cerebellum Deck (46)
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1

Cerebellum damage results in what kinds of deficits

equilibrium, tone or synergy deficits (all involve coordination of motor output)

2

Cerebellum connects to brainstem via…

peduncles: inferior and middle peduncles carry the major inputs to the cerebellum, and the superior peduncle contains the output.

3

Lobes of cerebellum

The primary fissure demarcates the boundary between the anterior and posterior lobes, while the postero-lateral fissure defines the border of the flocculo-nodular lobe.

4

alternate names for flocculo-nodular lobe

archicerebellum (oldest phylogenetically lobe) or vestibulocerebellum (receives inputs from vestibules)

5

What/where is the neocerebellum

Most recent lobe evolutionarily- comprises the lateral cerebellum and is made up of mostly posterior lobe and some anterior lobe

6

what/where is the paleocerebellum

Midportion of the anterior and posterior lobe

7

List the cerebellar nuclei from medial to lateral

fastigial, 2 globose, emboliform and dentate nuclei (globose and emboliform together referred to as the interposed nucleus)

8

List the deep cerebellar nucleus associated with each zone of cerebellum

Vermis: fastigial nuc. Paravermis: interposed nuc. Hemisphere: dentate nuc.

9

list corticonuclear zones

Medial/ vermal zone, intermediate/paravermal zone, lateral/ hemispheric zone

10

Function of vermal zone

Has output connections through fastigial nucleus and is involved in control of axial musculature, posture and balance, and integration of head and eye movements

11

function of paravermal zone

Has connections through the interposed nuclei to the red nucleus and fine tunes movements of the limbs

12

function of lateral zone

Has connections through the dentate nucleus and is involved in higher level coordination of movements, including planning and initiation of movements

13

function of flocculo-nodular lobe

Has connections with vestibular nucleus of brain

14

Function of deep cerebellar nuclei

Provide major output pathway of the cerebellum

15

efferent connections of vermal cerebellum

Sends information to the vestibular nucleus and the pontine reticular formation (bilaterally) from the fastgial nucleus. From there, information descends in the medial descending system by way of the lateral vestibulospinal tract and the pontine reticulospinal tract. Some neurons in the flocculo-nodular lobe send their axons directly to cells of the vestibular nucleus without synapsing in the fastigial nucleus. vermal cerebellum is involved in motor control having to do with equilibrium and posture.

16

Efferent connections of paravermal cerebellum

From the interposed nuclei, info is sent to contralateral red nucleus, directing motor output through the rubrospinal tract, part of the lateral descending system

17

efferent connections of lateral/hemispheric cerebellum

Sends info via dentate nucleus to contralateral ventrolateral thalamus and from there influences wide areas of cortex, particularly primary motor and associated motor cortex (pre-motor)

18

Where do afferent fibers from spinal cord go to in the cerebellum

vermal and paravermal cerebellum- results in a somatotopic map on the vermal and paravermal cerebellum, no on lateral cerebellum

19

describe somatic distribution in cerebellum

a double somatotopic distribution is found (one on anterior lobe, one on posterior lobe) with axial body surface found medially at the vermis and distal limbs laterally at paravermis. The head of the map is caudal in the anterior lobe and rostral in posterior lobe, such that there is a head to head representation of the body surface

20

Affrent input to lateral zone of cerebellum

The lateral zone doesn’t receive any direct primary afferent input. There is no somatotopic map in the lateral hemispheres. Instead, info from the contralateral cortex (primary and associated motor cortex) comes to the lateral zones by way of the pontine nuclei (axons synapse on ipsilateral neurons in basal pons then pontine neurons send axons contralaterally).

21

For flocculonodular lobe: list functional region, principal input, deep nucleus, principal destination and function

vestibulocerebellum, vestibular sensory cell input, vestibular nucleus, destination is axial motor neurons, functions include axial control, vestibular reflex (balance, eye movement)

22

For vermis: list functional region, principal input, deep nucleus, principal destination and function

spinoocerebellum, visual, auditory, vestibular and somatosensory input, fastigial nucleus, destination is medial descending systems, functions include axial motor control (posture, locomotion, gaze)

23

For paravermal lobe: list functional region, principal input, deep nucleus, principal destination and function

spinoocerebellum, spinal afferent input, interposed nucleus, destination is lateral system and red nucleus, functions include distal motor control

24

For lateral lobe: list functional region, principal input, deep nucleus, principal destination and function

cerebrocerebellum, cortical afferent input, dentate nucleus, destination is integration areas, functions include initiation, planning, timing

25

cerebellar deficits are always contralateral or ipsilateral

Ipsilateral- sensory input to the cerebellum is largely uncrossed, as are descending cerebellar outputs, while tracts btw cerebellum and cortex cross.

26

Cerebellar lesions have what effect on muscles

Loss of coordination and equilibrium, but NOT loss of sensation or strength

27

Which regions of cerebellum are most resistant to obvious motor effects when damaged

Lesions of cerebellar cortex have little obvious motor effect. To have a visible deficit, it must involve large regions of cortex, or lesions of underlying deep nuclei

28

Ataxia

loss of coordination or timing of involved muscles. Symptoms include past-pointing (aka dysmetria, patients inability to bring a limg to a required or desired point in space), decomposition of movement (aka dysdiadochokinesia), intention tremors perpendicular to direction of limb motion, nystagmus, slurred speech

29

Cerebellar cortex layers and cells found in these layers

1. Molecular layer (uppermost)- contains parallel fibers from granule cells, dendrites of purkinje cells and scattered inhibitory interneurons called stellate cells and basket cells. 2. Purkinje layer (middle)- purkinje cell bodies. 3. Granular layer (inner layer)- granule cell bodies

30

Info comes to cerebellar cortex through what fibers

mossy fibers (from wide variety of sources such as primary vestibular afferents and pontine nuclear cells), and climbing fibers (from contralateral inferior olivary nucleus) - both give off collaterals that excite cells in deep nuclei too

31

Describe pontine nuclei tract pathway

axons from pontine nucle on one side immediately cross midline to enter the middle cerebellar peduncle of the opposite side. The fibers of the middle cerebellar peduncle then enter the cerebellum to end as mossy fibers

32

Middle cerebellar peduncle contains what kinds of fibers

consists nearly entirely of axons going to the cerebellum from the pontine nuclei.

33

Describe flow of info via mossy fibers

Mossy fibers diverge extensively to excite a large number of granule cells, and each granule cell is contacted by numerous mossy fibers. Granule cells then excite purkinje cells via their parallel fibers. Each parallel fiber may contact hundreds of purkinje cells, and each purkinje cell is contacted by >200,000 parallel fibers

34

Distribution of climbing fibers

More discrete than mossy fibers- each climbing fibers contacts as few as a dozen purkinje cells, and each purkinje cell is contacted by only one climbing fiber. All parts of cerebellar cortex receiving climbing fiber input

35

climbing fibers tract pathway

Axons from inferior olive cross the midline immediately and enter the contralateral inferior cerebellar peduncle

36

What fibers are found in inferior cerebellar peduncle

Majority are fibers going to the cerebellum, but also contains fibers going from the cerebellum to the vestibular nucle

37

Compare complex to simple spikes

Climbing fibers form powerful synaptic contacts with purkinje fibers, such that single AP in a climbing fiber gives rise to a burst of spikes in Purkinje cell (called a complex spike). On the other hand, many parallel fiber inputs must sum to generate a single action potential in a Purkinje cell (called a simple spike)

38

What do Purkinje cells do

When activated, Purkinje cells are inhibitory onto cells of deep nuclei, turning them off. They are the only output from the cerebellar cortex. They also have a high rate of spontaneous activity, generating AP's without excitatory input. Thus they are continually suppressing activity of deep cerebellar neurons

39

Function of basket and stellate cells

Inhibitory interneurons. Parallel fibers excite these cells, which in turn inhibit Purkinje cells. This form of lateral inhibition results in DISinhibition of the deep cerebellar neurons, thus increasing their firing rate

40

Function of golgi cells

Inhibitory interneuron. Provide feedback inhibition of granule cell in glomerulus. Are excited by parallel fibers

41

8. Which cells of the cerebellar cortex have inhibitory actions?

basket cells, stellate cell, golgi cells,

42

Describe use of mossy fibers vs climbing fibers in motor learning

Purkinje fibers fire simple spikes arising from mossy fiber activity in synchrony with a trained movement. When that movement changes (ie, increased load), the Purkinje fiber fires complex spikes arising from climbing fiber activity. After a while, the complex spikes stop and simple spikes occur again at lower frequency than before. This occurs because the inferior olive generates climbing fiber activity (an error signal) when there is a discrepancy btw planned and actual motor performance. This leads to long term depression of sensitivity to mossy fiber input.

43

superior cerebellar peduncle contains what?

output from deep cerebellar nuclei (95%) and small amount of sensory info input

44

superior cerebellar peduncle pathway

axons cross midline in brainstem to reach red nucleus and VA/VL

45

pontine nucleus projections and inputs

Pontine nuclei project to contralateral cerebellum ending as mossy fibers and receive input from ipsilateral cerebral cortex, esp. motor and premotor cortex

46

Lesion in the cerebral peduncle would cause what

contralateral spastic paralysis in the entire trunk and extremities as well as contralateral weakness in the lower half of the face due to denervation of upper motor neuron input to the facial nucleus