Cerebellum Flashcards
1
Q
What are the basic functions of the cerebellum? Where is it located?
A
- IPSILATERAL control of coordination, posture/balance, and tone (it is entirely related to motor function)
- located posterior to the brainstem; it is part of the hindbrain
- basically, the cerebellum receives info on balance (vestibulocerebellum), proprioception of limbs (spinocerebellum), and what the mind wants/the overall goal (cerebrocerebellum), integrates all the info and then projects out to the necessary centers
2
Q
What are the three lobes of the cerebellum?
A
- (from superior to inferior:)
- anterior lobe
- posterior lobe
- flocculonodular lobe
3
Q
Which fissures divides the lobes?
A
- the primary fissure divides the anterior and posterior lobes
- the dorsolateral fissure divides the posterior and flocculonodular lobes
4
Q
What is the vermis? What lies on either side of the vermis?
A
- the vermis is a central depression found on the posterior aspect of the cerebellum
- on either side of the vermis is the cerebellar hemisphere, with a paravermal area between the two
- there are 2 full homunculi in the vermal and paravermal areas: the trunk and axial muscles lie within the vermis, and the limbs and appendicular muscles lie within the paravermal areas (ispilaterally)
5
Q
When is the cerebellum consulted in the generation of movement?
A
- it is consulted in between the generation of intention of movement and the firing of corticospinal fibers, as it contains the information the brain needs on the body’s initial position in order to generate smooth movement with minimal issues
- it is also constantly updated during the movement via unconscious sensory afferents to monitor the process for any fine-tuning
- involvement of the cerebellum is why we don’t over- or under-shoot objects we’re reaching for, why we can touch our nose with our eyes closed, etc.
6
Q
What type of issues develop with damage to the cerebellum?
A
- inability to rapidly start movements (dysdiadokokinesia), frequent over/undershooting, and loss of coordination (ataxia)
- note that these will be IPSILATERAL defecits
7
Q
What are the deep cerebellar nuclei? What role does each play?
A
- the cerebellar nuclei are responsible for cerebellar output
- (going from medial to lateral within a hemisphere:)
- fastigial nucleus: part of the vestibulocerebellar system (balance)
- globose nuclei: part of the spinocerebellar system (tone)
- emboliform nucleus: part of the spinocerebellar system (tone)
- dentate nucleus (large): part of the cerebrocerebellar system (coordination)
8
Q
Compare the two types of fibers projecting into the cerebellum.
A
- climbing and mossy fibers, both are stimulatory
- climbing fibers are olivocerebellar fibers; they project from the inferior olivary nuclei into the molecular (outer) layer of the cerebellar cortex; they produce asparate
- mossy fibers are all other fibers entering the cerebellum; they project into the granular (inner) layer of the cerebellar cortex; they produce glutamate
- as they ascend into the cortex, both types first branch off to and stimulate the deep nuclei before projecting to the cortex
9
Q
What are the three layers of the cerebellar cortex? Which cells are found in each? How are they connected?
A
- (from inner to outer layer:) granular, Purkinje, molecular
- the dendrites of the Purkinje cells extend into the molecular layer, while their axons project through the granular layer and onto the deep cerebellar nuclei
- the granular cells have axons that ascend into the molecular layer and then split into 2 long parallel fibers, which travel laterally along the molecular layer and communicate with many Purkinje cells
- also present in granular layer are Golgi cells, which communicate with the granular cells
- the molecular layer contains stellate and basket cells, which communicate with specific groups of Purkinje cells
10
Q
Which cells and fibers are stimulatory in the cerebellum? What about inhibitory?
A
- stimulatory: climbing fibers (aspartate), mossy fibers (glutamate), granular cells (glutamate), deep nuclei
- inhibitory: Purkinje cells (GABA), stellate cells (GABA), basket cells (GABA), Golgi cells (GABA)
11
Q
Follow the path of a climbing fiber.
A
- climbing fibers originate from the medullary olives, enter the cerebellum, stimulate the deep ganglia (via aspartate), and then project to the molecular layer of the cortex
- here, they stimulate the dendrites of the Purkinje cells, which will inhibit the deep nuclei (via GABA)
- (1 climbing fiber to 1 Purkinje cell)
12
Q
Follow the path of a mossy fiber.
A
- mossy fibers enter the cerebellum, stimulate the deep ganglia (via glutamate), and then project to the granular layer of the cortex
- here, they stimulate the granular cells, which in turn stimulate MANY Purkinje cells via their parallel fibers in the molecular layer (via glutamate), which will inhibit the deep nuclei (via GABA)
- (1 mossy fiber to MANY Purkinje cells)
13
Q
What is the role of the Golgi cells?
A
- these are GABAergic inhibitory cells found in the granular layer
- these are stimulated by mossy fibers and parallel fibers, and inhibit the granular cells to prevent the excessive firing of granular cells to many Purkinje cells (this is a form of autoinhibition, as the mossy fibers are therefore stimulating AND inhibiting the granular cells)
14
Q
What is the role of the stellate and basket cells?
A
- these are both GABAergic inhibitory cells found in the molecular layer
- these are stimulated by parallel fibers and inhibit specific groups of Purkinje cells, allowing for fine-tuning of which Purkinje cells will be stimulated (suppressing certain cells emphasizes the stimulation of others)
15
Q
Vestibulocerebellar System
A
- vestibular nuclei of the brainstem project mossy fibers into the cerebellum via the inferior cerebellar peduncle
- fastigial nucleus gets stimulated and projects back to vestibular nuclei (triggers the vestibulospinal tract and medial longitudinal fasciculus to alter activity of extensor muscles and CNs III, IV, and VI for eye movement) as well as to the red nucleus (triggers the rubrospinal tract to alter activity of flexor muscles)
- results in control of balance via vestibulospinal and reticulospinal tracts
