cerebellum

Question 1

Cerebellum damage results in what kinds of deficits

Answer 1

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

Question 2

Cerebellum connects to brainstem via…

Answer 2

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

Question 3

Lobes of cerebellum

Answer 3

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.

Question 4

alternate names for flocculo-nodular lobe

Answer 4

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

Question 5

What/where is the neocerebellum

Answer 5

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

Question 6

what/where is the paleocerebellum

Answer 6

Midportion of the anterior and posterior lobe

Question 7

List the cerebellar nuclei from medial to lateral

Answer 7

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

Question 8

List the deep cerebellar nucleus associated with each zone of cerebellum

Answer 8

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

Question 9

list corticonuclear zones

Answer 9

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

Question 10

Function of vermal zone

Answer 10

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

Question 11

function of paravermal zone

Answer 11

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

Question 12

function of lateral zone

Answer 12

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

Question 13

function of flocculo-nodular lobe

Answer 13

Has connections with vestibular nucleus of brain

Question 14

Function of deep cerebellar nuclei

Answer 14

Provide major output pathway of the cerebellum

Question 15

efferent connections of vermal cerebellum

Answer 15

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.

Question 16

Efferent connections of paravermal cerebellum

Answer 16

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

Question 17

efferent connections of lateral/hemispheric cerebellum

Answer 17

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)

Question 18

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

Answer 18

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

Question 19

describe somatic distribution in cerebellum

Answer 19

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

Question 20

Affrent input to lateral zone of cerebellum

Answer 20

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).

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

cerebellar deficits are always contralateral or ipsilateral

Answer 25

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

Question 26

Cerebellar lesions have what effect on muscles

Answer 26

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

Question 27

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

Answer 27

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

Question 28

Ataxia

Answer 28

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

Question 29

Cerebellar cortex layers and cells found in these layers

Answer 29

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

Question 30

Info comes to cerebellar cortex through what fibers

Answer 30

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

Question 31

Describe pontine nuclei tract pathway

Answer 31

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

Question 32

Middle cerebellar peduncle contains what kinds of fibers

Answer 32

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

Question 33

Describe flow of info via mossy fibers

Answer 33

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

Question 34

Distribution of climbing fibers

Answer 34

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

Question 35

climbing fibers tract pathway

Answer 35

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

Question 36

What fibers are found in inferior cerebellar peduncle

Answer 36

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

Question 37

Compare complex to simple spikes

Answer 37

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)

Question 38

What do Purkinje cells do

Answer 38

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

Question 39

Function of basket and stellate cells

Answer 39

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

Question 40

Function of golgi cells

Answer 40

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

Question 41

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

Answer 41

basket cells, stellate cell, golgi cells,

Question 42

Describe use of mossy fibers vs climbing fibers in motor learning

Answer 42

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.

Question 43

superior cerebellar peduncle contains what?

Answer 43

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

Question 44

superior cerebellar peduncle pathway

Answer 44

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

Question 45

pontine nucleus projections and inputs

Answer 45

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

Question 46

Lesion in the cerebral peduncle would cause what

Answer 46

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