Acetylcholine: a chemical messenger (neurotransmitter) released by cholinergic nerves in the striatumarea of the brain. It is involved in many brain functions, such as memory and control of motor activity. There appears to be an interplay between the actions of acetylcholine and dopamine.

Action tremor: a tremor that occurs or increases when the hand is moving voluntarily

Adjunctive: supplemental or secondary (but not essential) to the primary agent; sometimes used to describe medications to enhance levodopa therapy

Agonist: a chemical or drug that enhances the activity of a neurotransmitter such as dopamine

Akinesia: delay in initiating movement; inability to move; "freezing"

Ancillary: auxiliary; serving as an aid

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

Anxiolytic: an agent or a class of medications that reduce anxiety

Apoptosis: a form of cell death in which cells shrink and disappear; sometimes referred to as "cell suicide". In Parkinson’s disease, some scientists believe that the nerve cells in the substantia nigra portion of the brain die by apoptosis.

Ataxia: loss of balance

Athetosis: slow, involuntary movements of the hands and feet (see Dyskinesia)

Autonomic nervous system: the system that controls involuntary body functions

Blepharospasm: involuntary clinching of the eyelid

Blood-brain barrier: the protective membrane that separates the bloodstream from brain tissue

Bradykinesia: slowness of movement

Bradyphrenia: slowness in thought processing

Chorea: excessive involuntary movements, ranging from twisting or writhing to flailing movements of the extremities (see Dyskinesia)

Cogwheeling: a ratchet-like movement in the joints, characteristic of Parkinson’s disease

CT Scan: Computerized Tomography; a type of x-ray; also known as a CAT Scan

Delusion: false, fixed belief, not substantiated by sensory or objective evidence

Dementia: a range of symptoms such as disorientation, confusion, memory loss, impaired judgment, and alterations in mood and personality -- symptoms can arise from a variety of causes

DNA (deoxyribonucleic acid) : the basic chemical substance that makes up the gene

Dopamine: achemical messenger (neurotransmitter) in the brain that controls movement

Dysarthria: low voice volume or muffled speech

Dyskinesia: abnormal, involuntary, purposeless body movements that can appear as jerking, fidgeting, twisting, and turning movements; frequently induced by Parkinson medications. They may be mild (slight ankle twisting) or severe (uncontrollable writhing movements). Dyskinesias are usually felt during the time you are on when you have taken your medication; this is also called “peak dose dyskinesias”. Dystonia, athetosis, and chorea are forms of dyskinesias.

Dysphagia: difficulty in swallowing

Dystonia: involuntary spasms of muscle contraction which cause abnormal movements and postures (see Dyskinesia)

Endogenous: originating internally; developing from within, rather than caused by external factors; the opposite of exogenous

Essential tremor (ET): a condition more common than Parkinson’s disease, which often includes shaking of the hands or head, and an unsteady quality of the voice

Etiology: the causes or origins of a disease. The etiology of Parkinson’s disease is not known.

Exogenous: originating externally; arising from external rather than internal factors; the opposite of endogenous

Festination: short, shuffling steps

Free radicals: toxic substances that are continuously produced by all cells of the human body

Freezing: temporary, involuntary inability to take a step or initiate movement

Half life: the time taken for the concentration of a drug in the bloodstream to decrease by one-half. Drugs with a shorter half life must be taken more frequently.

Hallucinations: hearing sounds or seeing animals, objects or people that are not real

Hypomimia: decreased facial expression due to rigidity of facial muscles

Idiopathic: of unknown origin or without apparent cause (Idiopathic Parkinson’s disease)

Lewy bodies: pink-staining spheres found in nerve cells, considered to be a pathological marker for Parkinson’s disease

Livido reticularis: purplish or bluish mottling of the skin caused by certain Parkinson medications

Micrographia: small, cramped handwriting

MPTP: a chemical produced during an attempt to make a synthetic narcotic. MPTP produces a condition that mimics Parkinson’s disease

Myoclonus: abrupt, jerking movements of the arms or legs, usually occurring during sleep

MRI (Magnetic Resonance Imaging) : computerized images based on nuclear magnetic resonance of atoms within the body induced by radio waves

Neuroleptics: drugs that block dopamine receptors, usually prescribed to treat psychiatric symptoms

Neuron: a cell that generates or conducts electrical impulses to carry information from one part of the brain to another

Neurotransmitter: a chemical substance (such as dopamine, acetylcholine, or norepinephrine) that carries impulses from one nerve cell to another

Neurotrophic factors: substances that prevent nerve cells from dying

Norepinephrine: chemical transmitter involved in regulating the involuntary nervous system

Off-On phenomenon: sudden, unpredictable changes in motor performance by people on levodopa therapy; When medications such as levodopa relieve symptoms, you are in your “on” state. This means you can do your daily activities. When the medication does not work and the symptoms return, you are in your “off” state. This means you may not be able to do the things you want or need to do.

Orthostatic hypotension: a drop in blood pressure upon standing; can cause fainting

Palsy: paralysis of a muscle group

Pathogenesis: the production or development of a disease

PET (positron emission tomography) : an imaging method that allows one to see brain dopamine systems using an injection of a radioactive substance

Postural tremor: the rhythmic shaking of the hands with arms outstretched

Resting tremor:   one of the primary symptoms of Parkinson's disease; typically present in arm, leg, lips, chin or tongue; tremor occurs or worsens when at rest; decreases with active motions.

Rigidity: increased resistance to the passive movement of a limb

Striatum: the area of the brain that controls movement, balance, and walking

Substantia nigra: area of the brain where cells produce dopamine

Wearing-off phenomenon: reduced effectiveness of levodopa prior to the scheduled time for the next dose, resulting in decreased motor performance; If your symptoms return before your next dose of medication, it means you are in a “wearing off” state.

Sources: National Parkinson Foundation (US),, November 2007.

Young Onset Parkinson’s Association,, 2007.

PEP: Parkinson Education Program for Community Caregivers , Parkinson Society Canada Southwestern Ontario Region, 2007.