Flashcards in export_cerebellum Deck (51)
What are the functions of the cerebellum
It controls muscle tone, co-ordination, and equilibrium
What are the major components of the cerebellum
2. Medullary substance
3. Intrinsic nuclei
Convolutions in the cerebellum are called
What are the three lobes of the cerebellum
What are the nine lobules of the vermis
From a phylogenic perspective how can the cortex of the cerebellum be classified
What are the components of the archicerebellum
Flocculus and nodulus.
Involved with vestibular function
What are the components of the paleocerebellum
Anterior lobe rostral to the primary fissure - lingula, centralis and culmen.
Control muscle tone with inputs from the stretch receptors.
What are the components of the neocerebellum
Posterior lobe between the primary fissure and the lateral fissures: declive, folium, tuber, pyramis, and uvula.
Controls co-ordination with inputs from the contralateral cortex via pontine relay nuclei.
What are the three cerebellar cortical layers?
1. Molecular layer (most superficial)
2. Purkinje cell layer
3. Granular cell layer (most deep)
Features of the molecular cell layer of the cerebellum
Most superficial layer of the cerebellum. It contains basket and outer stellate cells. Axons from each basket cell touch 10 Purkinje cells.
Features of the Purkinje cell layer
Contains Purkinje cells. The myelinated axons here synapse with the deep nuclei and the lateral vestibular nucleus and send collateral fibers to excite Golgi type 2 cells.
Features of the granular cell layer
Contains granule cells and Golgi type 2 cells.
Features of the granule cells
Granule cells supply 4-5 dendrites to form a glomerulus and sends unmyelinated fibers to the molecular layer which bifurcate into parallel fibers and contact the Purkinje cell dendrites.
Features of the Golgi type 2 cells
Axons of the Golgi type 2 cells synpase in the glomeruli of the granular layer and send dendrites to the molecular layer which they synapse with parallel fibers.
Inputs to the cerebellum arrive via the
Superior, middle and inferior peduncles
The fiber tracts which provide cerebellar input are:
These fibers will all lose myelin in the cortex and end as mossy/climbing fibers.
With the exception of granule cells, climbing fibers and mossy fibers all cerebellar cells are inhibitory.
What are the 8 spinocerebellar tracts
1. Dorsal spinocerebellar
2. Ventral spinocerebellar
4. Rostral spinocerebellar
Features of the dorsal spinocerebellar tract
Convey proprioception from joints and muscle spindles of ipsilateral lower extremities and upper trunk to Clarke's nucleus in lamina 7 of the intermediate zone of the spinal cord.
These fibers then enter the inferior cerebellar peduncle to the cerebellar vermis and intermediate zone of the cerebellum as well as the fastigial and the interposed nuclei.
Features of the ventral spinocerebellar tract.
Conveys efferent copies of motor commands, and exteroceptive and proprioceptive information to the lower extremities.
Cell bodies are spinal border cells in the anterior and intermediate horns, the tract ascends b/l crosses within the spinal cord and enters the superior cerebellar peduncle where it partly crosses again but remains mostly contralateral.
Features of the cuneocerebellar tract
Conveys proprioception of the upper extremities in the fasciculus cuneatus but synapses in the accessory cuneate nucleus in the caudal medulla and enters the inferior cerebellar peduncle ipsilaterally.
Upper extremity equivalent to the dorsal spinocerebellar tract
Features of the rostral spinocerebellar tract
Upper extremity equivalent to the ventral spinocerebellar tract.
Provides internal feedback, ispilateral and enters the inferior cerebellar peduncle
Features of the trigeminocerebellar tract
Conveys information from the mesencephalic, chief sensory and spinal nucleus of 5.
Mesencephalic --> middle cerebellar peduncle --> dentate and emboliform
Chief sensory --> quadrangular lobe and tonsil
Spinal nucleus (crossed and uncrossed fibers)--> tonsil
Features of the vestibulocerebellar tract
Monitors head position, eye movement and equilibrium.
Conveys fibers from CN 8 --> inferior cerebellar peduncle -->ipsilateral flocculonodular
Conveys inferior and medial vestibular nuclei --> juxtarestiform body --> bilateral flocculonodular lobe and fastigial nuclei
Features of the tectocerebellar tract
Conveys auditory and visual reflex information from the tectum --> anterior medullary velum --> superior cerebellar peduncle --> anterior and posterior lobes.
Features of the reticulocerebellar tract
Conveys information from the medulla --> inferior cerebellar peduncle --> vermis
Pons/reticulotegmental nucleus --> middle cerebellar peduncle --> vermis.
What two types of fibers provide afferent output to the cortex
1. Mossy fibers
2. Climbing fibers
Features of mossy fiber input to the cortex
Mossy fibers from the spino/ponto/vestibulocerebellar tracts go to the granular layer to form the center of a glomerulus with a mossy fiber rosette. The mossy fiber stimulates granule cells vs Golgi type cells which inhibit them.
Each glomerulus contains: 1 mossy fiber; 20 dendrites of granule cells; Golgi type 2 cell's axons and dendrites.
Features of climbing fiber input to the cortex
Climbing fibers from the contralateral inferior olivary complex to the molecular layer where they synapse on Purkinje cell dendrites, granule cell parallel fibers and basket and stellate cells.