Medical Terms

Alphabetical glossary and definition of medical terms including words related to Spinal Cord Injury (SCI) and other medical conditions:

4-AminoPyridine (4-AP) - An experimental drug that eases symptoms for some with MS, particularly if you are more Heat Sensitive. 4-AP is a Potassium Channel Blocker that improves Conduction of Nerve Impulses, through Axons with or without DeMyelination. Its use may cause Seizure, Convultion, or Dizziness.

Acetylcholine - An excitory NeuroTransmitter that is produced and used by Cholinergic Neurons to communicate with each other.

ACTH - Abbreviation for AdrenoCorticoTrophic Hormone a Steroid produced by the Anterior Pituitary Gland, it stimulates the Adrenal Cortex to release several Hormones including Cortisol.

- ACTH is often used for Short-Term treatment of an acute exacerbation (attack), no value as a Long-Term treatment of Multiple Sclerosis due to its proven Side-Effects.

- A substance produced by the Brain that regulates the production of Steroids by the Adrenal Gland. This material can be produced artificially and is sometimes recommended by physicians to manage flare-ups of Multiple Sclerosis.

Acuity, Visual - Clarity of vision. Visual acuity is expressed as a fraction of normal vision. 20/400 means an Eye that sees at 20 feet what an average Eye sees at 400 feet.

Adrenal Glands - A collection of Sympathetic Nerve Cells specialized in a number of important respects. The Cortex secretes HydroCortisone (Cortisol). The Neurons of the Medulla synthesize NeuroTransmitters NorEpinephrine and Epinephrine (Adrenaline), the only source of Epinephrine that enters the Bloodstream.

- This activates the Sympathetic Neurons of the Blood Vessels by commanding their release of NorEpinephrine, which specifies types of stimuli that have little or no effect on the rest of the Automatic Nervous System (ANS).

- Sensory situations of: Emotional Excitement, Fear, Apprehension, Psychic Distress, Panic Reactions, Sexual Activity and Fight-Or-Flight Stimuli, activate many parts of the the Sympathetic Nervous Systems.

Amines - Are derived from the Amino Acid Tyrosine and are secreted from the Thyroid and the Adrenal Medulla.

Amino Acids - Chemical substances (building blocks of Protein) the body obtains from food.

Essential Amino Acids (Only obtained from food) Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine

NonEssential Amino Acids (Body Can derive them) Alanine, Argine, Asparagine, Aspartic Acid, Cysteine, Glutamic Acid, Glutamine, Glycine, Proline, Serine, Taurine and Tyrosine. Anesthesia - Loss of feeling (Pain and Touch Perception) over part or all of the body.

Anoxia - A condition or state that exists, when there is not enough Oxygen for tissue Oxygenation.

Anterior Horn - Nerve Ganglia in the Gray Matter of the Spinal Cord containing Motor Neurons. The Posterior Horn (top) contains Sensory Neurons, which directly command Skeletal Muscles, to perform quick or repetitive movements and are the final target of most Neural activity. Lesions in the Cerebrum, Basal Ganglia, Cerebellum, or Pyramidal Tracts affect their function. ex: Unstable gait, or Incoordinate fingers. Anterior Horn Cell (Anterior Horn Neuron) - A Motor Neuron in the Anterior Horn Gray Matter. These cells innervate Muscle Fibers directly to produce movement of body parts.

AntiBodies - Are complex GlycoProteins (ImmunoGlobulins) having a destructive impact on specific Antigens (ie, Germs, Parasites, Bacteria, and other foreign substances) that stimulated their formation, confering Immunity against exactly that Antigen. They are produced by Plasma Cells (B-Cells that have differentiated), in direct response to an Antigen's presence.

Antigen - A molecular protein or carbohydrate substance (Virus, Toxin, or Enzyme), which stimulates an "Immune Response". Any substance that triggers the Immune System to produce an AntiBody.

Antigen-Presenting Cell (APC) - A specialized type of Leukocyte, bearing cell surface Class II MHC (Major Histocompatibility Complex) molecules. APCs process and present Antigens to an Inducer, T-Cell, or Helper T-Cell. Examples: Macrophage, Neutrophil, Dendrite, and B-Cell

Anti-Inflammatory Drugs - Over-the-counter and prescription medications (Steroids) that are sometimes recommended to decrease inflammation. Aspirin and Ibuprofen are types of over-the-counter anti-inflammatory medications.

Aphasia - Loss of Speech expression or comprehension.

Apoptosis - Biologically programmed cell death - self destruction (Cell Suicide).

Aspiration - Inhaling food particles or fluids into the lungs.

Asymmetry - Unequal or out of balance. Not the same on the two sides of the body.

Ataxia - The inability to maintain balance, while walking. The failure of muscular coordination, poorly coordinated gait or limb movements. Ataxia is seen as a reeling, wide-based Gait and is one of the most obvious signs of damage to the Cerebellum, or its connecting Neural Pathways.

Atrophy - A loss of substance, it refers to the loss of bulk in a Muscle, Nerve, or an Organ that is shruken (Atrophied), from less than normal usage or from previous damage.

Atrophy, Optic - Pallor and loss of Blood Vessels on the Optic Nerve Head, as seen through the Ophthalmoscope. This is caused by the loss of Myelin or of Optic Nerve Fibers and Blood Vessels in the Optic Nerve.

AutoImmune Disease - A process in which the body's Immune System causes illness by attacking elements, such as particular cells or materials, that are normal and essential for health. The Immune System is the body's defense system against abnormal substances (such as Viruses or Bacteria) in the body. - In AutoImmune disorders, the Immune System attacks substances that are needed by (versus harmful to) the body.

Autonomic Nervous System - Regulates InVoluntary (UnConscious) body functions, such as the activity of the Cardiac Muscle; Smooth Muscles (ex: Stomach and in the Skin); controls the secretions of internal Glands (Hormones); and the functions of the Respiratory, Circulatory, Digestive, and Urogenital Systems. Its two divisions counter-act each other, in order to achieve the appropriate response: The Sympathetic Division - accelerates the Heart beat, constricts and dilatates Blood Vessels, dilates the Bronchi and inhibits the Digestive System. It is most active under all conditions of Stress - it prepares the body for physical action (survival).

The ParaSympathetic Division - slows the Heart Rate, increases Intestinal and Gland Activity, relaxes Sphincter Muscles, stimulates Sexual arousal, contracts Pupillary muscles, and increases Saliva production. This division prepares the body for rest and recovery; it is responsible for bodily functions which occur at rest, such as Digestion and Urine production.

Axons - Are elongated Processes (Nerve Fibers) of Neurons. They enhance the speed of transmitting Nerve Impulses (Conduction) from one Neuron to another, due to the combined benefits of their large diameters, Nodes Of Ranvier, and Myelin wraps.

Axonal damage (Wallerian Degeneration), loss, or Atrophy are the cause of permanent MS Disability. Axons have been simplisticly compared to electric wires; however, Axons are the part of Neurons that actively generate electric current (Action Potential), while wires passively conduct current. (Also See: MS Lesions & Axons and Disability)