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49 Cards in this Set
- Front
- Back
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How many lobes, cortical layers, deep nuclei, peduncles, and functional subdivisions of the cerebellum are there?
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3
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Name the lobes of the cerebellum
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Anterior, Posterior, Flocculonodular
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Name the 3 deep nuclei of the cerebellum.
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fastigial, interposed, dentate
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What parts make up the interposed nucleus?
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globose and embeliform
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Peduncles of the cerebellum?
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superior, middle, inferior
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Functional subdivisions of the cerebellum?
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spino-, vestibulo-, cerebro-
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Direction of neurons of each peduncle?
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superior: efferent (except gracile proprioceptive afferents of the ventral spinocerebellar tract)
middle: afferent inferior: mix |
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Are the lobes functionally discrete?
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No
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Location of inputs (from where to where)?
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Corticopontine to medial flocculonodular and lateral hemisphere.
Spinal and trigeminal to vermis and intermediate hemisphere. |
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Where does the dentate nucleus project, and what is the functionality?
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to the motor and premotor cortices. motor planning.
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Where does the interposed nuclei project and what is its functionality?
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to the lateral and descending systems.
motor execution along with the fastigial nucleus. |
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Where does the fastigial nucleus project and what is its functionality?
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to the medial descending systems. motor execution along with the interposed nuclei.
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Where does the vestibulocerebellum (flocculonodular node) project, and what is its functionality?
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to the vestibular nuclei of the medulla. balance and eye movement.
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What makes up the spinocerebellum, and what other names is it known by?
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the spinocerebellum is made up of the vermis and the intermediate hemisphere.
also known as the paleocerebellum. |
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What makes up the vestibulocerebellum, and what other names is it known by?
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the flocculonodular node and the immediately adjacent vermis.
also known as the archicerebellum. |
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What makes up the cerebrocerebellum, and what other names is it known by?
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the lateral hemisphere. also known as the neocerebellum, or the pontocerebellum.
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What functionality does the spinocerebellum posses?
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regulate body and limb movements.
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What inputs does the spinocerebellum receive and from where?
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proprioception from the dorsal collumns of the spinal cord, including the spinocerebellar tract, the trigeminal nerve, and from visual and auditory systems.
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What sensory maps does the cerebellum possess? Where are these maps located and what do they represent?
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there are 2 maps in the cerebellum (at least in rats).
the spinocerebellum maps the trunk and head, with some represented at the top and the rest at the bottom (of the vermis and intermediate). |
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What 5 cell types exist in the cerebellum?
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granule, stellate, basket, golgi, purkinje
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Are these neurons inhibitory or excitatory?
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only granule cells are excitatory - the rest are inhibitory.
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Where does the vestibulocerebellum receive inputs from, and what type of inputs are these?
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it receives vestibular, proprioceptive, and visual inputs from the vestibular nuclei.
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What are mossy fibers and what do they do?
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Mossy fibers are neurons originating in the spinal cord, the pons, and the reticular formation. they excite granule cells with signals called simple spikes at high frequency.
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What are climbing fibers and what do they do?
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climbing fibers are neurons originating in the inferior olive. they branch in the sagittal plane (orthogonal to the parallel fibers) and excite about 10 Purkinje cells, creating complex spikes.
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What does the spinocerebellum primarily do?
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refines movement
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What is the subconscious part of the dorsal column system?
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the spinocerebellar tract, which begins with spinal interneurons and reaches the cerebellum as the mossy fibers which influence Purkinje cell output via granule cell axons (the parallel fibers).
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What is the nucleus of Clarke
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the nucleus of Clarke is the first synapse in the spinocerebellar pathway, which runs from C8 to ~L2. It gives rise to the dorsal spinocerebellar tract and enters via the inferior cerebellar peduncle.
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Explain the entire path of the spinocerebellar tract?
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Originates as axonal fibers in the spinal cord, terminates ipsilaterally in the cerebellum, entering via the inferior cerebellar peduncle.
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What are the subdivisions of the spinocerebellar tract, where do they receive input from, and what are their functionality?
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Dorsal (posterior) spinocerebellar tract : muscle spindles : lower limbs
Ventral (anterior) " : Golgi tendon organs: lower limbs Spinocuneocerebellar tract : muscle spindles : upper limbs Rostral spinocerebellar tract : Golgi tendon organs : upper limbs |
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What sensory methods obtain the proprioceptive information for the spinocerebellar tract?
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The Golgi tendon organs (myelinated, quick conduction), which is located at the connection between muscle and tendon, and detects strain on the tendons, which cannot stretch like muscle.
Muscle spindles, which monitor length of muscles. |
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In the spinocerebellar tracts, which sub-tracts are crossed and which aren't? Where do these tracts enter the cerebellum?
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The "touch" afferents (dorsal spinocerebellar and cuneocerebellar) are uncrossed, and enter via the inferior cerebellar peduncle.
The proprioceptive afferents (ventral and rostral spinocerebellar tracts) are both crossed and enter via the superior cerebellar peduncle. |
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Describe in detail the route of the dorsal spinocerebellar tract? (one of the two somatic sensation routes of the cerebellum)
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Dorsal spinocerebellar axons from the lower extremity ascend in the gracile facicle, but split off to synapse in Clarke's nucleus/column, then ascending as the dorsal spinocerebellar tract, entering the cerebellum via the inferior cerebellar peduncle.
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Describe in detail the route of the cuneocerebellar tract? (one of the two somatic sensation routes of the cerebellum)
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The cuneocerebellar tract ascends ipsilaterally to the accessory cuneate nucleus, and enters the cerebellum via the inferior cerebellar nucleus.
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Summarize the spinocerebllar system.
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Dorsal
Spinocerebellar:
Trunk
and
lower
body
mechanoreceptor
input (uncrossed)
Cuneocerebellar: upper limb mechanoreceptor input (uncrossed) Ventral : proprioception via Iβ Golgi tendon organs (strain detectors), Iaα muscle spindles (length detectors), all from lower limbs. (crossed/double‐crossed pathway) rostral spinocerebellar: proprioception via Iβ Golgi tendon organs (strain detectors), Iaα muscle spindles (length detectors), all from upper limbs. Much smaller than ventral tract (crossed/double‐crossed pathway) |
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What are Purkinje cells?
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Purkinje cells are GABAergic cells, very large neurons with incredibly elaborate arbor, and receives massive inputs from the orthogonality orientated parallel fibers (up to 200,000). They are inhibited by basket and stellate cells, which synapse on the axon initial segment and dendrites respectively.
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What are the targets of the Purkinje cells of the cerebellum?
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The deep cerebellar nuclei.
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What is the inferior olive?
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A gray folded lamina, arranged in the form of an incomplete capsule, located in the medulla. Olivocerebellar fibers are neurons that have their cell bodies in the inferior olivary nucleus, and leave medially through the opening (the hilum), cross midline, and ascend into the cerebellum via the inferior cerebellar peduncle, forming the climbing fibers.
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Where does the inferior olive output?
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Solely to the cerebellum.
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What is the red nucleus?
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A phylogenetically older part of the motor system, largely vestigial in humans. It receives many inputs from the contralateral cerebellum and input from the ipsilateral motor cortex.
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What is the cerebrocerebellum concerned with?
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Mostly motor mangement of the cerebellum, but has many cognitive and perceptual function as well. Involved in planning movements and overvaluation sensory input and adjusting output accordingly.
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Where does the cerebrocerebellum receive cortical input from?
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Solely from the pontine nuclei.
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Where do the pontine nuclei project, and what do they terminate as?
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They project to the dentate nuclei and terminate as mossy fibers in the lateral cerebellar cortex. Purkinje cells then project back to inhibit the dentate nucleus.
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How does the Spinocerebellum influence the motor cortex?
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Via the red nucleus (via interposed and dentate nuclei) to the VL of the Thalamus.
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How does the Cerebrocerebellum
use feedback?
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The Cerebrocerebellum
is driven by corticopontine input, and feeds back to the motor cortex via the VPL.
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Explain the feed forward loops of the cerebellum.
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On their way to the cerebellar cortex climbing and mossy fibers excite the deep cerebellar nuclei via axon colaterals. Their excusion through the cerebellar cortex elicits a descending, inhibitory influence via Purkinje cells onto the same deep nuclei - this inhibition is the sole output of the cerebellar cortex.
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Explain the motor input path to the cerebellum.
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Starting in the motor cortex, which projects to the red nucleus, which projects to the inferior olive, which projects, via climbing fibers to the cerebellar cortex (molecular layer) and the deep nuclei (via axon colaterals). The deep nuclei can then project back to the motor cortex via the VPL.
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Explain feedback from the red nucleus.
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The cerebellum projects to the parvocellular (small-cell) domain of the red nucleus (the part which doesn't get input from the interposed nuclei) which projects to the inferior olive, which projects back to the cerebellum via climbing fibers.
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Explain the Marr - Albus theory of the cerebellum.
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The Marr - Albus theory is based on mathematical modeling of the cerebellar architecture proposes a model that explains how cerebellar cortical circuits enable motor learning.
Climbing fiber input to Purkinje cells weakens the cells response to mossy fiber input over time - parallel fiber-Purkinje cell synapses are affected as long-term depression. The depression helps select certain Purkinje cells to program or correct errors in eye or limb movements iterativly. |
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What are the three signs of Cerebellar damage?
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Ataxia:
innacuracy
in
the
speed,
force
and
distance
of
volitional movement – for example: patient overshoots or undershoots target when reaching for an object. Ataxia of gait results in lurching and staggering • Nystagmus (from Greek “to nod off"): a rhythmic involuntary oscillation of eye movements • Tremor: involuntary oscillation of movements of the limbs or trunk – typically pronounced when patient attempts an accurate reaching movement |
