atom

the smallest part of an element; indivisible by ordinary chemical means

Anatomy

the science of the structure of living organisms

Physiology

the science of the functioning of living organisms

cell

the basic biological unit of living organisms, containing a nucleus and a variety of organelles enclosed by a limiting membrane

molecule

particle consisting of two or more atoms held together by chemical bonds

tissues

a group of similar cells specialized to perform a specific function; primary tissue types are epithelial, connective, muscle, and nervous tissues

organ

a part of the body formed of two or more tissues that performs a specialized function

organ system

a group of organs that work together to perform a vital body function; e.g., nervous system

organism

an individual living thing

homeostasis

a state of body equilibrium or stable internal environment of the body

effector

an organ, gland, or muscle capable of being activated by nerve endings

negative feedback

a corrective mechanism that opposes or negates a variation from normal limits

ventral

anterior or front

posterior

toward the back; dorsal

positive feedback

feedback that tends to cause a variable to change in the same direction as the initial change; enhances the stimulus

inferior

below, in reference to a particular structure, with the body in the anatomical position

distal

farthest from the point of attachment of a limb or origin of a structure

cephalic

pertaining to the head

metabolism

the sum total of the chemical reactions that occur in the body

receptor

some type of sensor that monitors and responds to changes in the environment

element

any of the building blocks of matter; oxygen, hydrogen, carbon, for example

compound

substance composed of two or more different elements, the atoms of which are chemically united

ion

an atom with a positive or negative electric charge

salt

ionic compound that dissociates into charges particles (other than hydrogen or hydroxyl ions) when dissolved in water

catalyst

a substance that accelerates a specific chemical reaction but that is not altered by the reaction

inorganic compound

a compound that lacks carbon; for example, water

organic compound

a compound containing carbon; examples include proteins, carbohydrates, and fats

solution

a homogenous mixture of two or more components

proton

subatomic particle that bears a positive charge; located in the atomic nucleus

polar molecules

nonsymmetrical molecules that contain electrically unbalanced atoms

pH

the symbol for hydrogen ion concentration; a measure of the relative acidity or alkalinity of a solution

neutron

a fundamental particle that does not carry a positive or a negative charge

neutralization

(1) a chemical reaction that occurs between an acid and a base; (2) blockage of the harmful effects of bacterial exotoxins or viruses by the binding of antibodies to their functional sites

ionization

dissociation; the breakdown of a molecule in solution to form ions

matter

anything that occupies space and has mass

enzyme

a substance formed by living cells that acts as a catalyst in bodily chemical reactions

hydrogen bond

weak bond in which a hydrogen atom forms a bridge between two electron-hungry atoms; an important intramo-lecular bond

base

a substance that accepts hydrogen ions; proton acceptor; compare with acid

acid

a substance that liberates hydrogen ions when in an aqueous solution; compare with base

electrolyte

a substance that breaks down into ions when in solution and is capable of conducting an electric current

isotope

these vary in the number of neutrons they contain and they are different atomic form of the same element