Cerebellum
The cerebellum is a structure highly involved at ensuring the movement plans are refined, realistic (eg in line with the current body position), and general coordination.
Voluntary movements can occur without the cerebellum but they are clumsy and disorganised. (drunken gait for example is similar)
Anatomy of the cerebellum
The cerebullum has 2 hemispheres demarcated by the anterior cerebellar incisure, posterior cerebellar incisure, and the vermis. each hemisphere has 2 lobes, the anterior and posterior. However the functional divisions lie across different boundaries.
There are 3 main divisions of the hemispheres,
- Spinocerebellum This is the medial 50% of the cerebellum and works to balance the posture and movement of the trunk and limbs
- Cerebrocerebellum This is the lateral portions of the cerebellum and are important for planning movement
- Vestibulocerebellum The is is the flocculi and the nodulus which do balance, head and eye movements
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- deep nuclei The deep nuclei are 3 pairs of nuclei, the dentate, interposed and fastigial, which act to do calculations to refine the
Cerebellum physiology
There are 3 peduncles which connect the cerebellum to the brainstem, there is the superior, middle and inferior. These dont really look like distinct structures and are more sections of one large peduncle.
The SCP is most efferent information away from the cerebellum, and the MCP is mainly afferent to the cerebellum. The ICP does both directions.
Inputs: Inputs to the cerebellum are sensory data from the limbs, and motor plans from the motor cortex and premotor cortex.
Outputs: outputs to the spinal cord and the brainstem which directly influence motor control. and outputs tot he motor areas in the thalamus and the brainstem which helps refine movements.
Cerebellar cortex vs DCN
The cerebellar cortex is involved with comparing sensory data to motor data but the movement refinement, on the go correction as well as learning is chiefly handled by the DCN.
Some symptoms of cerebellar dysnfucntions are loss of cooridination in muscle activity which can present as:
- Ataxia Inaccuracy in the speed force and distance of a movement.
- Tremor Involuntary oscillation of the limbs or trunk
- Nystagmus Rhythmic involuntary oscillation of the eyes
- Headache & vomiting