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Module 7.3Movement Disorders
Parkinson’s Disease• A neurological disorder
characterized by muscle tremors, rigidity, slow movements and difficulty initiating physical and mental activity
• Associated with an impairment in initiating spontaneous movement in the absence of stimuli to guide the action
• Symptoms also include: – depression– memory and reasoning deficits– loss of olfaction
Parkinson’s Disease• Caused by gradual and progressive death of neurons,
especially in the substantia nigra.• Substantia nigra sends dopamine-releasing axons to the
caudate nucleus and putamen (of the basal ganglia)• Loss of dopamine leads to less stimulation of the motor
cortex and slower onset of movements.
Parkinson’s Disease• The basal ganglia is a group of large subcortical structures
in the forebrain important for initiation of behaviors.• Comprised of the following structures:
– caudate nucleus– putamen– globus pallidus
Parkinson’s Disease: Genetics• Studies suggest early-onset Parkinson’s has a genetic link.• Genetic factors are only a small factor to late on-set
Parkinson’s disease (after 50).
Parkinson’s Disease: Risk Factors
• Exposure to certain drugs (MPTP) • Environmental exposure to toxins, including
herbicides, insecticides, and fungicides• Head trauma
Parkinson’s Disease
• Cigarette smoking and coffee drinking are related to a decreased chance of developing Parkinson’s disease.
Parkinson’s Disease: L-Dopa Treatment
• The drug L-dopa is the primary treatment for Parkinson’s and is a precursor to dopamine that easily crosses the blood-brain barrier.– Often ineffective and especially
for those in the late stages of the disease.
• Does not prevent the continued loss of neurons.
• Enters other brain cells producing unpleasant side effects.
Parkinson’s Disease: Other Therapies
• Other possible treatments for Parkinson’s include:– Drugs that stimulate dopamine receptors or block the
breakdown of dopamine– Neurotrophins (chemicals that support cell growth)– Drugs that decrease apoptosis (cell death)– High frequency electrical stimulation of the globus pallidus– Transplant of neurons from a fetus– Stem cells: immature cells grown in tissue culture that are
capable of differentiating
Huntington’s Disease• A neurological disorder
characterized by various motor, cognitive, and mood symptoms.– affects 1 in 10,000 in the
United States– usually appears between
the ages of 30 and 50.• Associated with gradual and
extensive brain damage especially in the caudate nucleus, putamen, globus pallidus and the cerebral cortex.
Huntington’s Disease• Initial motor symptoms include
arm jerks and facial twitches.• Motors symptoms progress to
tremors and writhing that affect the persons walking, speech and other voluntary movements.
• Also associated with various psychological disorders:– Depression, memory
impairment, anxiety, hallucinations and delusions, poor judgment, alcoholism, drug abuse, and sexual disorders.
Huntington’s Disease
• Presymptomatic tests can identify with high accuracy who will develop the disease.– Controlled by an autosomal
dominant gene on chromosome #4.
– The higher the number of consecutive repeats of the combination C-A-G, the more certain and earlier the person is to develop the disease.
• No treatment is effective in controlling the symptoms or slowing the course of the disease.
Huntington’s Disease
• A variety of neurological diseases are related to C-A-G repeats in genes.
• For a variety of disorders, the earlier the onset, the greater the probability of a strong genetic influence.