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Organisation of the motor system
Visual cortex
Cerebellum
Somatosensory
cortex
Prefrontal cortex
Supplementary
motor cortex
Premotor
cortex
Motor nuclei
of the thalamus
Basal
ganglia
Primary
motor cortex
Brainstem
Extrapyramidal
Motor pathways
Pyramidal
tract
Motor system includes
• Tracts
Corticospinal tract (Pyramidal tract )
Extra-pyramidal system
• Basal Ganglia (regulator)
• Cerebellum
(regulator)
Corticospinal pathway
Basal Ganglia and Cerebellum
Motor regulators
Motor control systems outside the cortex
Cerebellum
-controls neural ‘programs’ for the
executionl of skilled movements
Basal ganglia
- a group of subcortical forebrain nuclei
(caudate nucleus, putamen (=
striatum),
globus palludus, subthalamic
nucleus)
- modulate patterns of motor activity
Forebrain
Input to
basal
ganglia
Midbrain
Output to
thalamus
and
cortex
Forebrain
Midbrain
MOVEMENT DISORDERS
Parkinson disease
Huntingtons disease
PARKINSONS DISEASE
• Effects dopaminergic neurons
• Neurons are lost from substantia nigra
• Rarely presents before 50 years
• Neurodegenerative disease
Neuropathology of Parkinson’s disease
• nigro-striatal pathway degeneration
• leading to a depletion of striatal dopamine
• some degeneration of other dopamine pathways too
Dopamine
Glutamate
XStriatum
GABA
CLINICAL FEATURES
Characterized by:
• Tremors
• Rigidity
• bradykinesia
Huntington’s disease
• Onset of symptoms usually at 30 to 45 years
• Genetically determined (single dominant gene)
• Causes degeneration of the output
neurones from the striatum, reducing
inhibitory modulation of motor function
•Progressive disease causing involuntary muscle
jerks
•
Dopamine
Glutamate
Striatum
X
GABA
HUNTINGTONS DISEASE
• Inherited disorder
• Autosomal dominant
• Males females equally affected
• Presents during the 4th decade
• Chorea which worsens with time NOT Sydenham
chorea
• Cognitive disorders
• Dementia
Motor control systems outside the cortex
Cerebellum
-controls neural ‘programs’ for the
executionl of skilled movements
Basal ganglia
- a group of subcortical forebrain nuclei
(caudate nucleus, putamen (=
striatum),
globus palludus, subthalamic
nucleus)
- modulate patterns of motor activity
GROSS STRUCTURE
Organisation of the motor system
Visual cortex
Cerebellum
Somatosensory
cortex
Prefrontal cortex
Supplementary
motor cortex
Premotor
cortex
Motor nuclei
of the thalamus
Basal
ganglia
Brainstem
Extrapyramidal
Motor pathways
Primary
motor cortex
Pyramidal
tract
Feed-back and feedback
control circuits
• Input:
Cerebellar connections
– Sensory cortex (somato, visual)
– Vestibular system
– Spinocerebellar tract
• Output:
– Motor cortex
– Thalamus motor nuclei
– Extra-pyramidal tracts
The main functions of cerebellum:
• body equilibrium
• regulation of muscle tone
• coordination of movements
Ataxia
• means disturbances of equilibrium of the body
and coordination of movements.
• Cerebellum lesion produces cerebellar ataxia
Cerebellar ataxia
•
Attactic gait – patient can’t to walk
•
Disorders of equlibrium – patient can’t to stand
•
Intention tremor – is dynamic tremor (it is more expressed
while moving and disappears while rest)
•
Nystagmus
•
Dysmetria (disturbed ability to gauge distances)
Ménière Disease
Disease results from a disruption of normal endolymph volume
Symptoms include: Severe vertigo
Positional nystagmus (nystagmus when head in a particular position)
Nausea
Affected individuals can also experience-unpredictable attacks of auditory & vestibular
symptoms:
Vomiting
Tinnitus (ringing in ears)
Inability to make head movements
Inability to stand passively
Low frequency hearing loss
Treatment: administration of a diuretic (hydrochlorothiazide) & a salt restricted diet
Persistent condition:
shunt implantation into swollen endolymphatic sac, or
delivery of a vestibulotoxic agents (gentamicin) into perilymph.