Cerebellum Flashcards
Through lesion studies, the cerebellum has been ascribed the basic functions of:
smoothing and sequencing of complex movements, supporting postural adjustments and eye movements, and playing a role in establishing and modifying motor programs
These functions of the cerebellum, are necessary for the everyday functions we take for granted and can be attributed to:
interactions with the ascending sensory pathways, vision, vestibular function, as well as cortical plans of movement.
What are the 3 lobes of the cerebellum?
- anterior
- posterior
- floculonodular
Is the lobe description anatomical or functional?
anatomical
The cerebellum runs under powerful ___________ control and it is the release of that _____________ that allows for normal patterned movement to occur.
inhibitory
inhibition
Externally, on the posterior edge of the cerebellum is a rounded “shelf” known as the:
cerebellar tnosils
What is the clinical significance of the cerebellar tonsils?
If intracranial pressure is increased in the posterior fossa, what occurs?
their clinical significance has to do with their position next to foramen magnum.
The tonsils can be forced through the foramen magnum, pinching the medulla.
What would pressure on the medulla due to cardiovascular and respiratory centers cause?
????
How does output from the cerebellum travel?
by way of neurons located in deep cerebellar nuclei.
Where do the deep cerebellar nuclei lie?
in the white matter of the cerebellum, deep to the cortical circuitry.
What are the 3 nuclei of the deep cerebellar nuclei?
- fastigial nucleus
- interposed (interpossitus n.)
- dentate nucleus
Cerebellar cortex =
a laminated region with an outermost layer that is basically acellular, made up of axons and dendrites, the molecular layer.
In the cerebellar cortex, the layer after (“second layers”) the outermost layer, is a sparsely populated layer of very large neurons, Purkinje cells that form:
the output of the cerebellar cortex
How to the purkinje cells influence the activity of the deep cellular nuclei?
by inhibiting them
Does this “second cerebellar cortex layer” receive afferent or efferent info?
one major afferent system.
What is the final layer of the cerebellar cortex?
granular cell layer, that is made up of many grandular cells.
What does the granular cell layer receive?
receives the majority of input from the afferent systems, mossy fibers. The axons of this layer form the majority of the axons in the molecular layer and synapse on the dendrites of the purkinje cells.
What two pathways travel through the superior cellular pathway?
- dentatorubrothalamic pathway
2. ventral and rostral spinocerebellar pathways
Describe the dentatorubrothalamic pathway:
primary efferent pathway of the SCP
Describe the ventral and rostral spinocerebellar pathways:
carrying integrated information of both sensory and motor activity from the ipsilateral cord. These pathways cross contralateral at a spinal cord segment level and then recross through the superior cerebellar peduncle
What fibers does the middle cerebellar peduncle carry?
pontocerebellar fibers
What does pontocerebellar fibers carry?
carry information relayed through pontine nuclei in the ventral pons. This relay receives cortical information from all parts of the cortex.
What pathways travel through the inferior cerebellar peduncle?
- dorsal and cuneocerebellar pathways
- olivocerebellar pathway
- trigeminocerebellar pathways
- vestibulocerebellar
- fastigovestibular
What do the dorsal and cuneocerebellar pathways carry?
carry specific joint and muscle information encoded by GTOs, muscle spindles, and joint capsule receptors.
What do the olivocerebellar pathway carry?
arises from the contralateral inferior olivary complex and gives rise to climbing fibers
What do the trigeminocerebellar pathways carry?
carry similar somatosensory information from the face, jaw, and extraocular eye muscles.
What do the vestibulocerebellar carry?
carries axons from the vestibular nuclei as well as direct fibers from vestibular apparatus.
What do the fastigovestibular carry?
carries an efferent pathway from the fastigial and interposed nuclei to the vestibular nuclei and reticular nuclei. Additionally, there are some purkinje cell axons that bypass the deep cerebellar nuclei and project directly to the vestibular nuclei.
What are the 3 functional divisions of the cerebellum?
- vestibulocerebellum
- spinocerebellum
- cerebrocerebullum
Vestibulocerebellum =
is made up of the flocculonodular lobe. This region receives input from the vestibular nuclei and apparatus and then sends that information back to influence vestibular nuclei function and reticulospinal pathwaeys. Its general function is to control equilibrium, eye movements, trunk and postural muscle tone.
Spinocerebellum =
contains the majority of the vermis and the paravermal zones, as well as much of the anterior lobe. It receives information from the spinal cord, auditory, visual, vestibular, trigeminal and motor cortex. Its output is to medial and lateral descending pathways (reticulospinal and vestibulospinal) through both the interposed and fastigial nuclei. It is involved in controlling limb movements and muscle tone for error correction resulting in coordinated movements. It functions more at proximal limb joints.
Cerebrocerebellum =
is made up of the lateral parts of the cerebellar hemispheres, primarily the posterior lobe. It receives information from widespread areas of the cortex via pontine nuclei. Its primary output is to motor and premotor cortex through the dentatorubrothalamic pathway. It functions in planning and coordination of voluntary movements, as well as the “memory” of those movements.
