A Factfile For The 'Little Brain'

The Cerebellum

Main Functions:
>Coordination and fine-tuning of movements
>Maintenance of balance and posture (information is sent from proprioceptors to the cerebellum to monitor the body’s position at a given moment in time meaning that body position can be altered if necessary)

To carry out these functions, the cerebellum needs 3 things:
>Motor plan: the cerebellum needs to know what muscles contract, when they contract etc
>Position sense information (i.e. proprioception): to monitor movements and see if they match the motor plan
>feedback (information is sent to the cerebellum to adjust body movements so that they match the body plan)

Damage to the cerebellum can lead to:
>uncoordinated movements (e.g. abnormal gait)
>speech problems (N.B: muscles are used for speech)
>difficulty balancing

Causes of cerebellar damage:
>Tumours
>Viral infections
>Genetic disorders causing cerebellar degeneration

Location:
>behind the brain stem, at the back of the brain

Gross Anatomy:
>Outer section: cerebellar cortex- contains gray matter
>Middle section: contains white matter with some cerebellar nuclei

3 Layers of the cerebellar cortex:
>Molecular layer (i.e. the outermost layer)
>Purkinje cell layer
>Granule cell layer (i.e. the innermost layer)

Components of the cerebellar cortex:
>Purkinje cells: these are output neurons coming from the cerebellar cortex; they use GABA (an inhibitory neurotransmitter) to inhibit neuronal activity in deep cerebellar nuclei.
>Granule cells: these are also found inside the cortex; they use an excitatory neurotransmitter to excite Purkinje cells.
>Climbing fibres and mossy fibres: they are both axons arising from different places to excite Purkinje cells, granule cells and cerebellar nuclei neurons.
N.B: The components listed above appear in every single circuit found in the cerebellum.
Fun Fact: The cerebellum only makes up about 10% of the total brain volume but houses about 80% of the total number of neurons found in the brain, most of which are granule cells.
Inputs and outputs of the cerebellum:
>Inputs: climbing fibres, mossy fibres [they receive information from the motor cortex and the spinal cord]
>Outputs: cerebellar nuclei neurons [they travel to different areas of the brain, i.e. back to the spinal cord and the motor cortex]

The Future:
>New evidence suggests that the cerebellum may actually be involved in some higher order processes as well as movement. For example, some patients with cerebellar degeneration are thought to have cognitive and emotional difficulties (i.e. psychiatric disorders such as schizophrenia and ADHD).

Sources:
>https://nba.uth.tmc.edu/neuroscience/m/s3/chapter05.html
>http://vanat.cvm.umn.edu/NeuroLectPDFs/LectCerebellum.pdf
>The Brains Explained: The Cerebellum YouTube video

By Kumaran Rajaratnam







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