The cerebellum:

Cerebellum: Principally a motor organ Responsible for: Regulation and control of muscle tone Coordination of movement, especially skilled, voluntary movement Control of posture and gait

Motoric movements: Willed: Cortical. Pyramidal motor system Automatic: Static, postural. An expression of the extrapyramidal motor system Coordination of willed movements

Extrapyramidal system: Cerebellum Basal ganglia

Cerebellum: None of the motor activities of the cerebellum reach conscious kinesthetic perception: It`s main role is to assist in the initiation and modulation of willed movements that are generated in the cerebral hemispheres

3 Parts: Flocculonodular lobe. Oldest portion. Archicerebellum. Afferent fibers = proprioceptive impulses from vestibular nuclei. Equilibrium. Vestibulocerebellum

Anterior lobe: Paleocerebellum Spinocerebellum Proprioceptive fibers from muscles and tendons. Dorsal spinocerebellar tract (lower limbs) and ventral spinocerebellar tract (upper limbs). Maintains posture and muscle tone.

Posterior lobe: Neocerebellum Afferent fibers from cerebral cortex via the pontine nuclei and brachium pontis. Pontocerebellum Coordination of skilled movements that are initiated at a cerebral cortical level

Clinical signs in cerebellar disease: Hypotonia Ataxia, Nystagmus Incoordination Disorders of equilibrium and gait

Basal ganglia:

Anatomic considerations: No precise definition Caudate nucleus + Lentiform nucleus with it`s 2 subdivisions: Putamen Globus Pallidum

Physiology: “Brake and switch” theory The basal ganglia function as a brake or switch The tonic inhibitory (brake) action of the basal ganglia prevent their target structures from generating unwanted motor activity Switch function: Refers to the capacity of the basal ganglia to select which motor program will be active at any given time

Other theories: “Motor programming”: Role of the basal ganglia in the initiation, sequencing and modulation of motor activity.

Several motor syndromes: Loss of voluntary movement with spasticity: Corticospinal tract involvement Incoordination: Cerebellum Involuntary movements—dystonia: Basal ganglia

Symptoms of basal ganglia disease: Motor disorders: Deficits = negative symptoms or, Involuntary movements = positive symptoms (effects)

Negative: Bradykinesia, akinesia, loss of postural reflexes. Positive: Tremor, rigidity, involuntary movements—dystonia, chorea etc..