551 Lecture 18: Cerebellum

True or false: the cerebellum receives input from all parts of the nervous system

True

Vestibulocerebellum helps manage and maintain _____ and ____

Vestibulocerebellum helps manage eye movements and balance

Vestibulocerebellum output is to the ____ and ____

Vestibulocerebellum output is to the fastigial nucleus and vestibular nuclei (direct)

Vestibulocerebellum receives input from the ____ system via the ____

Vestibulocerebellum receives input from the vestibular system via the inferior cerebellar peduncle

Output from cerebrocerebellum goes to the ___

dentate nucleus

The activation of Purkinje cells is ____(direct or indirect) for mossy fibers

indirect

Output of spinocerebellum is through the ____

interposed nuclei

What are the deep cerebellar nuclei and their locations?

1) Fastigial nucleus - most primal and medial 2) Interposed nuclei-- lateral to fastigial 3) Dentate nucleus -- most lateral (and recent evolutionarily)

What are the three divisions of the cerebellar cortex and what do they do?

1. Anterior lobe/spinocerebellum-- regulation of muscle tone, coordination of skilled voluntary movement (ongoing limb movements), distal muscles, walking 2. Lateral cerebellar hemispheres/ neocerebellum or cerebrocerebellum-- planning and modulation and initiation, speech, complex motor programs, voluntary activity, storage of procedural memories 3. Flocculonodular lobe/vestibulocerebellum-- maintenance of balance, equilibrium and posture, control of eye movements

Describe the three cellular layers of the cerebellum from superficial to deep.

1. Molecular layer (largely devoid of cells). Mostly what it is full of are the dendrites of the Purkinje cells and the axons from the Granule cell layer. Also have modulatory interneurons known as stellate cells. 2. Purkinje cell layer. Mostly just cell bodies of Purkinje cells. Occasional astrocyte basket cell (interneuron) 3. Granule cell layer-- full of granule cells. Will find an occasional golgi type II cell (inhibitory interneuron)

What are the most prominent symptoms following damage to the cerebellum?

1. hypotonia 2. ataxia (intention tremor, inaccurate targeted limb movements) 3. Dysarthria 4. Nystagmus 5. Posture problems

Climbing fibers come in from the ____ via the ____ and have a (direct/indirect)__:__ relationship to Purkinje cells with ____ as the (excitatory/inhibitory) neurotransmitter being released.

CLIMBING FIBERS come in from the INFERIOR OLIVE via the INFERIOR CEREBELLAR PEDUNCLE and have a DIRECT 1:1 relationship to Purkinje cells with GLUTAMATE as the EXCITATORY neurotransmitter being released.

Cerebrocerebellum gets input from the ____ via the ____

Cerebrocerebellum gets info from the cerebral cortex via the pontine nuclei (middle cerebellar peduncle)

Climbing fibers activate Purkinje cells ____ (directly or indirectly)?

Climbing cells activate Purkinje cells directly. One single climbing fiber comes in and activates one single Purkinje cell.

Dentate nucleus sends info to ____outside of the cerebellum

Contralateral red nucleus/thalamus (coordination)

Each granule cell gives rise to 1 ____ fiber.

Each granule cell gives rise to 1 parallel fiber.

T or F: Mossy fibers have a direct input to Purkinje cells, while climbing fibers have a indirect input to Purkinje cells.

F. Mossy fibers have an indirect input through granule cells, while climbing fibers have a direct input to Purkinje cells.

T or F: removal of the cerebellum affects sensory perception.

F. Removal of the cerebellum does not affect sensory perception, but adjusts output of descending motor systems.

T or F: Any increase in input to the cerebellar cortex via the mossy or climbing fibers excites cerebellar Purkinje cells, which results in decreased inhibition of the deep cerebellar nuclei, and an increase in deep cerebellar nuclei output of the cerebellum. This is because Purkinje cells release GABA, which is excitatory.

F: Any increase in input to the cerebellar cortex via the mossy or climbing fibers excites cerebellar Purkinje cells, which results in INCREASED inhibition of the deep cerebellar nuclei and a DECREASE in deep cerebellar nuclei output of the cerebellum. This is because Purkinje cells release GABA, which is INHIBITORY.

T or F: Input to Purkinje cells is inhibitory?

F: Input to Purkinje cells is excitatory (glutamate)

True or false: Purkinje cells have a relatively small dendritic tree projection

False; huge dendritic tree

Fastigial nucleus, which is the most ___ located of the cerebellar nuclei, projects to the _____outside of the cerebellum

Fastigial nucleus, which is the most medially located of the cerebellar nuclei, sends information to the VESTIBULAR NUCLEI/RETICULAR FORMATION (extensor muscles)

feed forward information, which is (define) would be carried in the ____ peduncle.

Feed forward information, which is the "copy" of the motor plan that is copied to the cerebellum and coming through the motor cortex/premotor cortex, would be carried into the cerebellum via the MIDDLE CEREBELLER PEDUNCLE.

Feedback information from the periphery would be carried in the _____ peduncle

Feedback info from the periphery would come into the cerebellum through the INFERIOR CEREBELLAR PEDUNCLE

____ is released as a neurotransmitter by mossy fibers AND climbing fibers.

Glutamate (depolarizing/ excitatory)

Mossy fibers from spinal cord, sensory systems, and cerebral cortex connect to the ____ cells in the ____ layer.

Granule cells in the granule cell layer (deepest layer)

If you activate a mossy fiber you activate a ____ cell via a ____ cell.

If you activate a mossy fiber you activate a Purkinje cell via a granule cell.

Explain long term synaptic depression.

If you pair the two types of inputs into the cerebellum at the same time (mossy fiber and climbing fiber) what results is long term synaptic depression. Synaptic depression: The input from the parallel fibers (via the mossy fibers) to the Purkinje fibers is reduced (about 1/2).

Describe intention tremor.

Inaccurate movements (slow adjustments as you try to make precise movement) because you have to primarily use visual information to adjust motor programming in absence of cerebellar functioning.

Climbing fibers

Inferior olive

Inputs from inferior and middle cerebellar peduncles are 2 types of inputs into the cerebellar cortex: ____ and ____

Inputs from inferior and middle cerebellar peduncles are 2 tpyes of inputs into the cerebellar cortex: mossy fibers and climbing fibers

Interpose nuclei (globose nucleus and emboliform nucleus) are situated _____ and project to the ____outside of the cerebellum

Interpose nuclei (globus nucleus and emboliform nucleus) are situated lateral to the fastigial nucleus and project info to the contralateral red nucleus (origin of the rubrospinal tract) and the ventrolateral (VL) thalamic nucleus (flexor tone)

Mossy fibers and climbing fibers excite the ___ as well as granule cells via collateral connections.

Mossy and climbing fibers excite the DEEP CEREBELLAR NUCLEI as well as granule cells.

Mossy fibers activate ___ cells, which send (how many axons?) up into the _____ layer and bifurcates and activates ____ cells.

Mossy fibers activate GRANULE cells, which send ONE SINGLE AXON up into the MOLECULAR LAYER and bifurcates and activates PURKINJE cells.

____ cells, which release ____ (which is excitatory/inhibitory) as the neurotransmitter, are the sole output of the cerebellar cortex

PURKINJE CELLS, which release GABA (which is INHIBITORY) as the neurotransmitter, are the sole output of the cerebellar cortex.

____ fibers go in-between dendritic fields of Purkinje cells; these are the go-betweens from the granule cells to the Purkinje cells.

Parallel fibers go in-between dendritic fields of Purkinje cells. Each Purkinje cell will receive input from tens of thousands of parallel fibers.

In the end, all inputs (mossy fibers and climbing fibers) to the cerebellum act to excite _____ cells.

Purkinje

What are the afferent impulses to the brianstem?

Reticular nuclei (brainstem), vestibular nuclei (brainstem), and spinocerebellar tracts (SC), pontine nuclei (brainstem), and olivary nuclei (brainstem).

Mossy fibers

Spinal cord, other sensory systems, cerebral cortex (from pontine nuclei)

Spinocerebellum receives input from ____ system via the ____

Spinocerebellum receives input from the peripheral sensory system via the inferior cerebellar peduncle.

T or F: All of the output for the cerebellum goes through the deep cerebellar nuclei, except that some of the output goes direct to the vestibular nuclei.

T

T or F: Cerebellum acts as a comparator, receiving info about plans (MCP) and performance (ICP), and providing output to adjust action and intention.

T

T or F: Cerebellum plays an important role in motor learning and sensorimotor recalibration

T

T or F: Info from reticular nuclei, vestibular nuclei, and spinocerebellar tracts send information to the same side of the cerebellum that they originate from, while pontine fibers and olivary nuclei cross over to the opposite side of the cerebellum.

T

T or F: Over half of the neurons in your brain are cerebellar granule cells (cerebellar granule cells are the most numerous brain cells)

T

T or F: Purkinje cell axons are the sole output of the cerebellar cortex (they are what contact the deep cerebellar nuclei).

T

T or F: The output from the vestibulocerebellum bypasses the deep cerebellar nuclei and goes direct to the vestibular nuclei

T

T or F: Cerebellum helps us adapt to new sensory inputs.

T (e.g. beer goggles and rapid adaptation to new visual information)

T or F: the Cerebellum is necessary for VOR (normal vestibulo-occular reflex) adaptation

T.

From where does the inferior cerebellar peduncle (afferent) receive info?

The a) inferior olive in the medulla, b) spinal cord via medulla, and c) vestibular nucleus in the medulla --> inferior cerebellar peduncle

Via which peduncle does the cerebellum project info to cortical areas (efferent)?

The deep cerebellar nuclei send info (efferent) through the superior cerebellar peduncle to the VL complex (thalamus) and primary motor and premotor cortex.

From where does the middle cerebellar peduncle receive info (afferent)?

The frontal-motor/parietal cortex --> pons --> middle cerebellar peduncle