Cerebellum - Structure and functions
Definition
This part of the brain is concerned with co-ordination of muscular movements, maintenance of posture and balance
Situation
It is situated behind the pons varolii
Below the posterior portion of the cerebrum
In the posterior cranial fossa
Structure
Has two hemispheres
Narrow median strip called vermis
Greay matter on the surface
White matter in the depth
Cerebellum function
Receives most forms of sensory input
Adjusts rate, range, force and direction of movements to achieve most efficient movement
Is involved with the co-ordination of voluntary movements on the background of necessary balance, equilibrium and muscle tone
Seat of motor learning
Compares result of motor command with expectation
Powerful timing and sequencing function
Important in "putting the brakes on" a movement at the appropriate time
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Spinocerebellar pathways
Muscle spindle pathways to the cerebellum
Collaterals from the spindle afferents on one side of the body synapse in the grey matter of the spinal cord
From there second order neurones pass messages either ipsilaterally along the cord to the ipsilateral cerebellar hemisphere or contralaterally along the cord to the same (ipsilateral) hemisphere). The symmetrical arrangement is true of spindle afferents from the opposite side of the body.
Cerebellar cortex structure
Two kinds of input to the cerebellar cortex via mossy and climbing fibres (possibly for comparison). Only one kind of output - inhibitory utilising GABA via Purkinje cells to deep cerebellar and brainstem nuclei.
Cerebellar disease
Ataxia
Dysdiadochokinesia
Dysmetria
Dysynergia
Scanning speech
Diseases of pyramidal tracts
Stroke - partial or complete paralysis with spasticity
Cerebral palsy - with spasticity
Multiple sclerosis - with spasticity
