action potential - (also known as spike or impule) a rapid change in membrane voltage ("potential") from negative (-70 mV in nerve cells) to positive and then back to negative.  This causes an electrical current that proceeds down an axon.

adsorb - to form a thin layer of molecules of a substance on the surface of a solid or liquid.

amino acids - molecules that contain an amino group (NH2) and a carboxyl group (HCO2) with a subunit coming off of the alpha carbon (the carbon between the amino and carboxyl group).  There are twenty natural amino acids and they serve as the building blocks of proteins.  .

anemia - a condition where your red blood cells do not carry enough oxygen, usually because the number of red cells is too low

anesthetic - a chemical that makes you lose feeling and awareness.  A general anesthetic is one that will cause you to lose consciousness.  A local anesthetic will cause a loss of feeling in a particular area or part of the body.

antigen - anything (usually a protein) that elicits an immune response.  Bacteria and viruses are two examples of antigens.

alleles - One of a set of alternate forms of a gene. An example is the different alleles of eye color. Each of the different forms of the gene code for eye color, only each codes for a different color i.e. blue, brown, green.

bacteria - single celled micro-organisms that can be free living or live in/on other organisms.  

bile - a greenish-yellow fluid excreted from the liver into the small intestine, near the attachment to the stomach.  This fluid helps emulsify or dissolve fats so the body can absorb them.  Bile consists of cholesterol, bile salts, and worn out red blood cells. An imbalance in these chemicals leads to gallstones.  

bipolar disorder - a personality disorder in which the person oscillates between a deep depression and elation or happiness.  Usually the changes are gradual, but can be very sudden.  This disorder used to be called manic depressive disorder

blood transfusion - the process of transferring blood from one person (donor) to another person (recipient).  This may be done as a life saving technique for someone who has lost a lot of blood from a surgery or accident.

carbohydrates - compounds composed of only carbon, oxygen, and hydrogen.  Carbohydrates consist of starches and sugars, such as glucose. Glucose is  necessary for production of energy, especially in the brain.  

carcinogen - anything that is known to cause cancer.

cartilaginous - composed of or relating to cartilage.  Cartilage is a somewhat elastic tissue that is present in embryos but is then slowly replaced by bone as the infant grows; however, some cartilage remains, such as in your nose, respiratory passage, joints, and external ear.

centrifuge - a machine that rotates (spins) rapidly and uses centrifugal force to separate substances of different densities. You've used a centrifuge before. Have you ever watched a washing machine on spin cycle? A washing machine uses centrifugal force in the spin cycle to separate the water from your clothes.

chromatography - a way of finding out which substances a mixture contains by passing it through or over something that absorbs the different substances at different rates.

chromosomes - The self- replicating genetic structures of cells containing the DNA that bears in its sequence the cell's array of genes. In prokaryotes (bacteria), chromosomal DNA is circular, and the entire genome is carried on one chromosome. Eukaryotic (mammalian and other higher organisms) genomes consist of a number of chromosomes whose DNA is associated with different kinds of proteins.

chronic - of long duration or frequent occurrence 

compromise - as used in biology, it means to cause the impairment of; to injure or weaken

cross section - a cut through a structure or tissue that is perpendicular to its main axis. 

curare - a muscle relaxant used in anesthesia

cytoskeleton - parts of the cell that give it structure and hold things 
together - typically proteins

debris - parts or fragments of something that has been broken down.

degeneration - the breaking up of cell structures in association with death of a cell.

dementia - severe loss of brain capability that interferes with social ability or ability to work.

denature - a protein is said to be denatured if it unfolds or uncoils so that its function is abolished even though the primary string of amino acids remains intact.

diabetes - a chronic condition of having abnormally high levels of sugar (glucose) in the blood.  This disease is usually caused by a deficiency in insulin, an enzyme that lowers the blood's glucose level.  The excess glucose in the blood is excreted through urine.  The body needs this glucose to make energy.  For example, the brain only uses glucose to make energy.  Without enough glucose, the brain will stop functioning.    

dialysis - a procedure in which a special machine, called a dialysis machine, filters out waste products from a person's blood.  The filtering is based on  the rates of diffusion for different substances in the blood as they pass through a permeable membrane.  

diffusion molecules have energy, so when they are dissolved in water
they move around a lot. The motion of any one atom or molecule has no particular
direction, but a whole population of molecules will eventually get distributed more or
less uniformly in the solution. Think about what happens if you put a drop of ink in a glass of water.

diphtheria - a potentially deadly infectious disease that attacks the upper respiratory tract.  It occurs when the bacterium, Corynebacterium diphtheriae, infects the body. 

duodenum - the first part of the small intestine.  During digestion, bile is released from the gallbladder into the duodenum.  

ecosystem - a group of interdependent organisms and the environment they live in and depend on.

electric charges - atoms acquire an electric charge when they have too many
electrons (negative charge) or too few electrons (positive charge). Positive charges
attract negative charges, and like charges repel each other. Think of the static that
can develop on the screen of a TV set. This charge attracts oppositely charged dust, paper, 
or other material..

electron micrograph - A picture taken by a very high powered microscope that magnifies enough to see large molecules. In both light and electron microscopes, illumination is provided by a source (lamp, filament in the electron gun) which is focused by a condenser lens onto the specimen. A first magnified image is formed by the objective lens. This image is further magnified by the projector lens onto a ground glass screen (light) or fluorescent screen (electrons).

elution - to remove one substance from another by washing it out with a solvent. For example, rinsing an adsorbed material from the surface it is attached to.

endoplasmic reticulum - structures outside the nucleus of a cell that contain RNA. This is where protein synthesis actually takes place

enzyme - a protein that speeds up chemical reactions in living organisms.  Enzymes lower the energy necessary to turn a set of reactants into other products.  Without enzymes, we could not exist.  

extensor muscles - in most cases, muscles that straighten joints (as opposed to flexing a joint).

extraction - separation of a material (substance) from a mixture by dissolving one or more of the substances in a solvent

facilitate - to make something easier to do

fermentation - the breakdown of an energy-rich compound in anaerobic (without oxygen) conditions.  Bacteria break down nutrients through fermentation, but the human body also uses fermentation.  Vigorously contracting muscle cells and red blood cells both use fermentation to produce energy. 

filtrate - fluid that has passed through a filter.  The filter removes some components of the original fluid.  For example, lymph is a filtrate of the blood that does not have red blood cells nor some of the proteins that blood does have.

flexor muscles - in most cases, muscles that bend joints so that the attachments move closer together and are found on front of body.

fluid mosaic - the model used to describe the structure of cell membranes. Fluid- refers to the motion of the molecules in the membrane. The molecules are able to move, like molecules in a liquid, instead of being stationary, like molecules in a solid. Mosaic-something consisting of a variety of elements. In this case, a cell membrane is made up of several different kinds of lipids and proteins.

food chains - the sequence of food and nutrient distribution among different species. For example, small plant cells in water are eaten by small fish, small fish are eaten by big fish, big fish are eaten by people

Golgi apparatus - a long, twisted tube or backbone to which newly
formed proteins attach and complex sugar molecules are attached 
to the certain newly formed proteins

gradient - a measure of change in a physical quantity, such as concentration or temperature, over a specified range or distance.

hemoglobin - a large, protein compound that carries oxygen in the blood.  It is made of up four heme groups with a molecule of iron  in the middle.  The iron molecule gives the hemoglobin its bright red color when oxygen is attached.  When oxygen is not attached, the hemoglobin changes shape and its color to a deeper bluish red tint.

heredity - the transmission of qualities from parent to offspring through the genes. Also see inherit.

homogenous - same, alike, or unvarying in consistency, or components

immiscible - describes two or more liquids that will not mix together to form a single homogenous (unvarying) substance.

inherit - to receive a trait from a parent (or ancestor.) You inherit bodily traits such as eye color from your parents. Also see heredity.

insomnia - a disorder in which the person can't seem to get a good night's sleep.  This can be due to the fact that the person can't fall asleep at all, keeps waking up in the night and then can't fall back asleep, or just does not feel rested after sleeping.

inspired air - air that is breathed in from the outside environment

intoxication - to make drunk with alcohol, drugs or other substances. When using intoxication to describe an effect of a substance on the body (the pathology of a substance) intoxication also means poison or to poison someone.

ions - an atom that has lost or gained one or more electrons.  Thus,
a positively charged ion is one that has lost an electron and a negatively
charged ion is one that has gained an electron.

jaundice - a yellowing of the skin, usually showing up in the whites of the eyes, fingernails, and other lightly pigmented parts of the body surface. There are three main causes: 1) accumulation of a breakdown product (called bilirubin) of excessive destruction of red blood cells (bruises often have localized jaundice in the early stage of healing), 2) a failure of the liver to remove the normal amounts of bilirubin, or 3) failure of elimination of bilirubin via the bile that is normally made in the liver and dumped into the intestine as a waste product.

ketones - a class of body chemicals in which part of the molecule contains a carbon-oxygen bond (C= O).These form from the breakdown of fats and proteins in the liver. The can accumulate to toxic levels if the blood sugar falls too low (as in certain diabetes situations, starvation, or eating a high fat-low carbohydrate diet). They are toxic because they make the body fluids too acid for enzymes to work properly.  

kinetic energy - energy associated with motion. A rock rolling down a hill has kinetic energy. Also see potential energy.

lesion - an abnormal change in any tissue or organ due to disease or injury.  The lesion caused by ulcers involved a hole in the tissue.

lipids - Lipids are also known as fats, but they include compounds of many different kinds. Chemically, these compounds are built on a backbone of glycerol, which was a three-carbon chain. Each carbon, in turn, bonds via an oxygen molecule to so-called fatty acids.   Fatty acids have an acid group (COOH) at one end that is attached to a chain of carbons. Lipids differ mainly in the nature of the fatty acid chains.

 low density lipids:  lipids that help transport cholesterol from the liver to the tissues.  Hence, they are considered the "bad" kind of lipid

high density lipids: lipids that help transport cholesterol from the tissues to the liver for excretion into bile. Hence, they are considered to be a good kind of lipid.

lymphocytes - small white blood cells that are responsible for the immune response.  There are two main types of lymphocytes: B-cells and T-cells.  B-cells produce antibodies that attack bacteria and other toxins.  T-cells directly attack and destroy cells infected with a virus or cancerous cells.  

molecules - When two or more atoms bond together, they are called
molecules. Examples include water (H2O - two atoms of hydrogen and
one of water), carbon dioxide (C02 - one atom of carbon and two atoms 
of oxygen)

neuron - a nerve cell.  These cells conduct electricity in the form of action potentials (pulses of electricity) throughout the nervous system in the body.

nitrites - chemicals that contain a nitrogen and oxygen atom (NO) that are made from nitrates by microbes in the gut or soil. Nitrates provide the nitrogen content in fertilizer. Obviously, farm animals can be poisoned by eating fertilizer and even plants that have been over-fertilized.  These are poisonous because they bind to hemoglobin and keep it from carrying oxygen in the blood. In large enough concentrations, nitrites and their reaction products can promote cancer. See for information on nitrites/nitrates in drinking water.

obsessive-compulsive disorder - an anxiety disorder in which the person has obsessive, repetitive thoughts and compulsively performs certain actions that are senseless and distressing (such as constantly cleaning or counting).  

opacity - ability of material to stop light. For example, muddy water is
more opaque (cloudy) than clear tap water. Opacity is expressed as a comparison
between light striking the material and light transmitted.

organelles - Literally, the term means "little organs." Inside a cell, there are various little structures that perform specific functions, much like the multicellular organs of our body do.  In the cell, these include generating energy (the organelle is the mitochondrion), making proteins (the organelles are ribosomes and Golgi apparatus), and others.

osmosis - the movement of a solvent (like water) from an area of lesser to greater concentrations so that the solvent will be evenly distributed. So for example, if you put a cell in pure water (that has no dissolved chemicals in it), the water outside would move inside to increase the concentration
of water inside the cell.  Because most of the dissolved material in a cell cannot get out (to lower the concentration of water outside the cell), water will keep coming inside until it bursts the cell. This movement of water is a special case of the principle of diffusion, which applies to dissolved substances, which also tend to distribute evenly if there are no barriers

ozone - (O3) a very reactive form of oxygen that is a natural component of the upper atmosphere and helps to reduce harmful radiation from the sun.  However, in the lower atmosphere (the air we live in) ozone is a pollutant and very destructive.

partition - to separate something into different parts or sections.

permeability - the speed at which a membrane will allow substances to pass through it.

phagocytosis - the process by which certain cells destroy toxins and other organic matter by wrapping their cell membrane around it, and incorporating it into the phagocytic cell, where enzymes break down the chemicals and destroy them.

phosphate bonds (high energy) - adenosine diphosphate has two phosphate groups bonded like this: O - P - O - P.  The ADP can capture external energy and store it in a third phosphate group.  The bond that holds the third phosphate group to the molecule has high energy and can readily release it. A similar principle applies to other compounds that store energy in phosphate bonds.

phospholipids - Phospholipids are typical lipids, except that a phosphate group (POO4) is bonded to one end of one of the fatty acid chains. See lipids.

porous - containing pores, or holes that permit the movement of fluids or gases. An example of a porous material is a sponge. Porosity is the extent to which a substance contains pores. Swiss cheese has high porosity compared to cheddar.

portal vein - a large vein that carries nutrients, such as carbohydrates and amino acids, from the stomach and small intestine to the liver for detoxication.  

post-traumatic stress disorder - a common anxiety disorder that occurs after a severe tragedy in which the person was in grave danger or thought they were in grave danger.  Family members or close friends can also get the disorder when someone experiences a grave tragedy.  Common symptoms include flashbacks of the event, sleep disturbances, depression, anxiety, irritability, and outbursts of anger. 

potential energy - energy that an object (or piece of matter) has because of its position, or an arrangement of its parts (for example chemical bonds.) A rock at the top of a hill has potential energy. Also see kinetic energy.

proteins - molecules made of long strings of repeating units, called amino acids.
Amino acids have carbon, hydrogen, oxygen, and nitrogen in them. When they
attach to each other in long strings, they coil. The coiled folds back on itself to
form an irregularly shaped clump.

reflex - any response that occurs automatically without conscious effort.

renal - relating to or involving the kidneys

rupture - break or bust open

solvent - a material (usually a liquid) in which other substances are dissolved

stimulus - anything that causes a neuron to react.  Sometimes the stimulus is so small, that the neuron does not fire (does not send information) and the person does not "feel" anything or react to the stimulus. 

substrate - fluid or solid in which an item is placed, or environment in which something may function. For example, a fish's substrate is water. In this case, the substrate that the protein is placed into is a jello-like gel. In chemistry, the substrate is also whatever is acted upon, for example, and antibody's substrate is the part of the germ it attacks.

sucrose - a type of sugar. Sugars are carbohydrates.

sugar - compounds that contain only carbon, hydrogen, and oxygen, usually in a ring 
structure of 5 or six carbons. Common table sugar (sucrose) is the  best known example, but there are 
other kinds of sugar; it has two molecules of the body's most common sugar, glucose.

toxin - a poisonous agent produced by certain animals, plants, and bacteria.  A toxin usually has a large molecular weight and is antigenic. 

unipolar depressive disorder - (also known as clinical depression) a disorder in which the person to dives into a deep depression for weeks to years (if not treated).  About one in five Americans will experience some type of depression at least once in their lifetime.

ventral - the lower side or underneath

virus - a microorganism, smaller than bacteria, that invades a cell and uses the cell's metabolic systems to reproduce.  A virus consists of either DNA or RNA surrounded by a protective coat.  Unlike most bacteria, viruses cannot live on their own, they have to have a host cell to survive.

vitamins - organic molecules that are essential to our bodies but only in very small quantities.  Vitamins do not, in themselves, provide energy, but they help our bodies carry out metabolic processes to make energy.

volatile - quickly vaporizable (turns to gas) at low temperatures.  Volatile chemicals are usually very reactive and dangerous.

white blood cell - (one main type is called a. leukocyte)  One of the cells in the immune system that helps fight invaders.  The white blood cell count (WBC)  increases when a foreign antigen, such as bacteria or virus, enters the body.  A normal WBC is between 4,000 and 11,000 white blood cells per microliter.