Acetylcholine: a chemical transmitter (messenger) in the striatum area of the brain.

Action Tremor: a tremor that develops or increases when limb or body are moving voluntarily.

Agonist: a chemical or drug that enhances the activity of a neurotransmitter.

Akinesia: inability to move; "freezing."

Anticholinergic: a drug which blocks the action of acetylcholine.

Antioxidant: agent that prevents the loss of oxygen in chemical reactions.

Artane (trihexyphenidyl): an anticholinergic drug. Ataxia: loss of balance.

Athetosis: slow, involuntary movements of the hands and feet.

Autonomic nervous system: controls involuntary activities.

Axon: the long, hairlike extension of a nerve cell that carries a message to another nerve cell.

Basal Ganglia: several large clusters of nerve cells deep in the brain below the cerebral hemispheres; crucial in coordinating motor commands. Include the striatum and the substantia nigra.

Blood-brain barrier: the membrane that seperates the blood from brain cells.

Benign essential tremor: condition characterized by tremor of hands, head, vocal chords, and sometimes other parts of the body. It is sometimes mistaken for Parkinson's disease.

Bradykinesia: slowness of movements; a cardinal sign of Parkinson's disease.

Bradyphrenia: slowness of thought processes. Bromocriptine: (Parlodel) a dopamine agonist - a drug.

Carbidopa: a drug that is used in combination with levodopa (Sinemet) to treat PD. Carbidopa prevents levodopa from being metabolized in the body, allowing more levodopa to reach the brain.

Cogwheeling: slow, jerking movements.

Chorea: excessive motor activity ranging in severity from restlessness and twitching, to flinging movements, sudden jerks and spasms.

Dendrite: a threadlike extension of a nerve cell that serves as an antenna to receive messages from the axon of other nerve cells.

Deprenyl (Eldepryl or Selegiline): a monoamino oxidase B (MAO-B) inhibitor which increases the effects of dopamine in the brain - a drug.

DOPA: short name for dihydroxyphenylalanine, an amino acid.

Dopa decarboxylase: enzyme found in the nervous tissue and blood; it controls conversion of DOPA to dopamine.

Dopa decarboxylase inhibitors: (Ex. carbidopa) drugs that block the conversion of levodopa to dopamine outside the brain (so that more DOPA can reach the brain.) Dopamine: a chemical substance derived from DOPA, found in the brain; acts as a neurotransmitter governing movements, balance, and walking; is deficient in Parkinson patients.

Dopamine agonist: a drug that mimics the effects of dopamine and stimulates the dopamine receptors. Dysarthria: difficult, poorly articulated speech.

Dyskinesia: abnormal involuntary movement. Dysphagia: difficulty in swallowing.

Dystonia: slow twisting involuntary movement, associated with forceful muscle contractions or spasms.

Enzyme: a substance that speeds up a chemical reaction.

Extrapyramidal system: the system of nerve cells, nerve tracts and pathways that connects the cerebral cortex, basal ganglia, thalamus, cerebellum, reticular formation, and spinal neurons. It is responsible for the regulation of reflex movements such as balance and walking. The extrapyramidal system is damaged in Parkinson's disease.

Festination: short, shuffling steps.

Freezing : temporary, involuntary inability to move. Idiopathic: disease of unknown origin or without apparent cause. Levodopa (L-DOPA): is changed into dopamine in the brain - a drug.

Lewy bodies: pink staining spheres, found in nerve cells, that are considered to be a marker for Parkinson's disease.

Micrographia: change in handwriting where script becomes small. Monoamine oxidase inhibitors: drugs which enhance the effect of certain chemical transmitters like dopamine, by inhibiting the function of enzymes that oxidize them (break them down).

MPTP: a chemical produced during an attempt to make a synthetic narcotic. MPTP destroys the cells of the substantia nigra and produces a condition that mimics Parkinson's disease.

Myoclonus: jerking, involuntary movements of one muscle or group of muscles, in the arms and legs. Neuron: a cell specialized to generate and/or conduct electrical impulses and to carry information from one part of the brain to another. Neurotransmitters (or transmitters): chemical substances that carry impulses from one nerve cell to another.

Norepinephrine: chemical transmitter involved in governing the involuntary nervous system.

On-off phenomena: sudden changes in performance by patients on levodopa therapy.

Orthostatic hypotension: a rapid decrease in blood pressure upon standing. It may cause fainting. Palsy: paralysis of a muscle or group of muscles. Parlodel (bromocriptine): a dopamine agonist - a drug.

Pergolide (Permax): a dopamine agonist - a drug.

Permax (Pergolide): a dopamine agonist - a drug. Resting Tremor: tremor of the limb or body while the body is at rest.

Rigidity: increased resistance to the passive movement of a limb.

Sinemet: a combination of an inhibitor (carbidopa) with levodopa--the carbidopa blocks the conversion of levodopa to dopamine outside the brain - a drug. Sinemet CR: a time-release form of Sinemet.

Striatum: area of the brain controlling movement, balance, and walking; connects to and receives impulses from the substantia nigra.

Substantia nigra: area of the brain where cells produce dopamine.

Symmetrel (amantadine): releases dopamine from substantia nigra cells - a drug.

Thalamotomy: surgical procedure where a small region of the thalamus is destroyed.

Tremor: a rhythmical shaking of a limb, head, mouth, tongue or other part of the body.

Wearing off phenomena: waning of the effect of previously administered levodopa, associated with abrupt changes in performance.