Cerebellum Flashcards
Cerebellum function
In voluntary movement
In posture and equilibrium
Primarily inhibitory function
What percentage of the brain’s neurons does the cerebellum have
Consists of ~10% gross brain volume but is highly convoluted and contains >50% of the brain’s neurons.
Cerebellar inputs and outputs
The cerebellum operates in 3’s:
there are 3 main inputs
there are 3 main outputs from 3 deep nuclei.
The 3 routes are the peduncles, or “stalks” - the rostral, middle and caudal cerebellar peduncles.
Cerebellar peduncles
Cerebellar peduncles carry axons into and out of the cerebellum
One pair (cranial): out of cerebellum (Efferent)
2 pairs: (middle & caudal): afferent to cerebellum.
Inputs of the cerebellum
The inputs are:
Mossy fibers from:
Corticopontocerebellar pathway
Spinocerebellar pathways
Reticular nuclei (brainstem)
Vestibular nuclei (brainstem)
Climbing fibers from the inferior olive of medulla
Cerebellar Afferent pathways
Cerebellar circuits
Three layers and only 5 types of neurons throughout the cerebellar cortex:
Stellate cells: inhib.
Basket cells: inhib.
Golgi cells: inhib.
Granule cells: excit
Purkinje cells: inhib.
The 3 layers of the cerebellum
Molecular layer
Purkinje cell layer
Granule cell layer
Molecular layer
Outermost (molecular layer) consists primarily
- granule cell axons, known as parallel fibers;
-dendrites of neurons located in deeper layers
-scattered inhibitory interneurons: (the stellate and basket cells)
The primary input fiber axons to cerebellum
Climbing fiber: from medulla
Mossy fiber: from higher brain, brainstem and spinal cord
Mossy fibers and climbing fibers
Directly excite cerebellar nuclei neurons, or their inputs can be integrated to affect Purkinje cell response
Input/output organization of the cerebellum:
Normally, effect of interaction slightly favors excitation of deep nuclei; hence, there is continuous moderate stimulation of deep nuclei
The three deep nuclei of the cerebellum
The 3 deep nuclei are:
1. Vermis–> Fastigial–>vestibular and reticular nuclei
- Lateral zone–>Dentate–>thalamus, red nucleus, cerebral cortex
3.Intermediate–>Interposed–>thalamus and red nucleus
All 3 receive inputs from sensory afferent tracts and from the cerebellar cortex.
Fastigial
Concerned with balance; sends information mainly to the vestibular and reticular nuclei
Dentate and Interposed nucleus
Both concerned with voluntary movement; send axons mainly to the thalamus and red nucleus
Major efferent pathways
To medullary and pontine regions of the brainstem – posture and equilibrium
To thalamus , cortex, basal ganglia, red nucleus, & reticular formation – coordination between agonists and antagonists
To thalamus , cortex – coordination of sequential motor actions
Vestibulocerebellum
Helps coordinate balance and eye movement
Pathway:
1. either body or head movement
2. Vestibular sensory (inner ear)
3. Flocculonodular (cerebellum)
4. Vestibular motor (brain stem)
5. alpha and gamma motor neurons (brainstem and spinal cord)
6. Muscle tone & head movement with eye position
Spinocerebellum
Helps coordinate muscle tone + limb movement
Cerebrocerebellum
Helps with planning coordinated, properly timed movement sequences
