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Glossary of Terms

activation energy – the minimum amount of energy required to allow a chemical reaction to occur

action potential – an electrical signal that travels down the length of the neuron (axon) before being converted into a chemical signal at the synapse

active transport – the movement of molecules against the concentration gradient with the help of a transport protein. This transport requires energy in the form of ATP.

alcohol dehydrogenase – the enzyme responsible for metabolizing alcohol. It catalyzes the conversion of alcohol to acetaldehyde, a toxic compound.

alleles – a subset of (related) genes that each occupy the same position on the chromosome

anesthesia – a state of reduced consciousness, generally induced by a drug during surgery

anions – negatively charged atoms or molecules

apoptosis – a form of death initiated by individual cells that follows a genetically “programmed” series of steps

aqueous – any solution in which water is the solvent (a water-based solution)

astrocytes – “star cells”, neuroglial cells provide nutrition and support to neurons; they contribute to the blood-brain-barrier.

Attention Deficit Hyperactivity Disorder (ADHD) – a neurodevelopmental disorder characterized by inappropriate levels of inattention, hyperactivity and impulsivity.

axon – a long portion of the neuron that leaves that cell body (or soma) and carries chemicals, proteins, and electrical impulses to the nerve terminal

binge drinking – consumption of four or more alcoholic drinks on a single occasion for women (for men, consumption of five or more drinks).

blackout – an inability to remember key events that occurred while drinking alcohol due to a temporary loss in the ability to encode memories

blood alcohol concentration – the amount of ethanol in grams dissolved in a deciliter (100mls) of blood

blood-brain-barrier – capillaries in the brain consisting of tightly packed endothelial cells and an astrocyte “wrap;” only drugs that are lipophilic can move across by passive diffusion.

catalyst – a substance added to a chemical reaction to speed up the rate of the reaction without being consumed in or produced by the reaction.

cations – positively charged atoms or molecules

caudate nucleus – located within the basal ganglia, the caudate nucleus plays an important part in the brainÕs learning and memory and voluntary motor systems.

cell cycle – the life cycle of an individual cell including defined stages of growth, DNA replication, and reproduction

cerebellum – the part of the brain in the back of the head that controls balance for walking and standing, and other motor functions.

cerebral cortex – the outermost layer of the cerebrum that plays an important role in memory, attention, thought, language, and consciousness.

cognitive – the process of thought.

condensation – the transition of a gas to a liquid

corpus callosum – a large bundle of nerve fibers in the brain which connect one hemisphere to the other.

Dalton – a unit of mass used to describe the weight of a molecule (also known as the molecular weight or formula weight in grams/mole)

dendrites – small protrusions radiating from the neuron cell body. They are covered with little spines that contain receptors to which neurotransmitters and drugs bind.

deoxyribonucleic acid (DNA) – a large molecule containing genes that provide the instructional code for the synthesis of proteins. DNA consists of two complementary polynucleotide chains coiled around each other in the form of a double helix.

dependence – with repeated use, the body functions normally in the presence of the drug. When the drug is not available, the body goes through a withdrawal syndrome. Alcohol withdrawal can be fatal.

depressant – a compound that slows electrical impulses in the brain to decrease alertness and increase fatigue

dipole – when two equal but opposite charges are separated between atoms in a molecule

distillation – the process of purifying or concentrating a solution by converting it to a gas (vapor) and then cooling the purified vapor back into a liquid.

endothelial – cells that make up blood vessels and capillaries

enzyme – a protein that catalyzes the rate at which a reaction occurs. It binds to one of the reactants, changing its structure to form a different molecule. It facilitates the chemical reaction.

epithelial – cells in the body that have access to the external environment such as skin, nasal passages, and the gut

equilibrium – a state in which the ratio of the concentrations of a compound in two compartments achieves a constant value

Executive function – an important thinking ability to plan, organize, manage, and perform tasks

fenestrae – small spaces or pores within endothelial cells that form the capillary membrane. These pores allow charged drugs or larger drugs to pass through the capillaries.

fermentation – when yeast metabolizes sugar to yield ethanol and carbon dioxide

fetus – a developing mammal prior to birth

filtration – a form of passive transport that describes the movement of small solutes through pores in the cell membrane with the concentration gradient

GABA – gamma-amino butyric acid; an amino acid neurotransmitter that reduces the firing rate of neurons

genetic polymorphism – when a gene exists in multiple forms within a population

glia – cells in the brain that make myelin to provide support and protection for the neurons

gliogenesis – generation of glial cells from neuronal stem cells

glutamate – an amino acid neurotransmitter that increases the firing rate of neurons

hippocampus – literally meaning “curved horse;” the seahorse shaped brain structure of the brain associated with emotions and the formation of memories

hydrogen bonding – when a hydrogen atom covalently bonded to a strongly electronegative atom (like oxygen) forms a weak bond with the unshared pair of electrons of a neighboring electronegative atom (like oxygen or nitrogen)

hydrophilic (literally, “water-loving”) – indicates a compound or substance that readily dissolves in water

hydrophobic (literally, “water-fearing”) – indicates a compound or substance that is more soluble in fat than in water. Hydrophobic compounds have longer chains of carbon atoms.

inert – an element or substance that is unreactive

interstitial – space between two tissues through which small molecules can pass

ion – an atom, radical, or molecule that has gained or lost one or more electrons. Therefore it acquires a net negative or positive charge.

lipophilic – “lipid-loving;” a compound that is soluble in fat but not water

lumen – the open space or hollow compartment inside an organ (stomach or small intestine) or blood vessel (capillary) of the human body.

macrophage – a type of white blood cell that engulfs foreign materials and cell debris to destroy them

messenger ribonucleic acid – also abbreviated mRNA or messenger RNA. It is transcribed from DNA and moves into the cytoplasm of the cell to direct (as a template for) protein synthesis.

metabolism – the chemical processing of a compound to yield energy or products for use by the body, or for elimination from the body

molecular formula – a formula that identifies the name and number of each atom in a molecule

monomorphic – when a gene exists in only a single form in a population

myelin – the fatty coating that surrounds and insulates the axon of a neuron to help to speed up the impulse flow; the “white matter” in the brain.

necrosis – a form of cell death initiated by external stimuli including injury or nutrient deprivation

neurogenesis – the birth of new neurons

neurons – the major cell type in the brain and spinal cord

neurotransmitters – chemical “messenger” molecules that are synthesized, stored, and released by neurons in response to an electrical impulse

non-polar – a chemical property of a substance that indicates an even distribution of charge within a molecule. A non-polar molecule is miscible in organic solvents.

organic – any compound that contains the atom, carbon. Ethanol, a two carbon alcohol, is an organic molecule.

organogenesis – development of the organs

oxidation – the donation of electrons to another atom often, by removal of a hydrogen (H+ atom)

oxidized – when a compound has donated electrons in a redox reaction

partition ratio – the ratio of the concentration of ethanol, for example, that resides in the blood (liquid) relative to the alveolar air (gas above the liquid) at equilibrium

passive diffusion – the movement of a molecule with its concentration gradient across a biological membrane. No energy is required.

placenta – an organ that connects the developing fetus to the mother to allow exchange of nutrients, waste, and gases (oxygen and carbon dioxide)

polar – a chemical property of a substance that indicates an uneven distribution of charge within the molecule—it is miscible in water.

postsynaptic – pertaining to the membrane of the receiving neuron (containing the receptors) at a synapse

prefrontal cortex – the front area of the brain that is important for executive function and decision-making

presynaptic – pertaining to the membrane of the axon terminal at a synapse

pulmonary circulation – the blood flow from the right side of the heart to the lungs, and then back to the left side of the heart

pyloric sphincter – a muscle between the stomach and small intestine. The pyloric sphincter controls the movement of stomach contents into the small intestine.

radical – an atom, molecule, or ion that contains an unpaired electron; it is very likely to take part in a chemical reaction

reactive oxygen species – molecules containing oxygen with an unpaired electron in its valence shell, making the whole molecule very reactive

receptor – a protein to which neurotransmitters, hormones, and drugs bind. Receptors are usually located on cell membranes and elicit a function once bound.

redox-reaction – any chemical reaction involving both oxidation and reduction

reduced – when a compound has accepted electrons in a redox reaction

reduction – the gain of electrons from another atom, often by addition of a H+ atom

ribosomes – structures within the cytoplasm consisting of proteins and a different form of RNA (rRNA) that support the process of protein translation

sedation – a state of drug-induced sleepiness

short-term memory – the temporary (seconds – minutes) storage of small amounts of information

soma – cell body, or region of a neuron containing the nucleus and protein synthesis machinery

stem cells – undifferentiated cells whose fate has not yet been decided; they can divide to form many different types of specialized cells.

structural formula – a formula that identifies each atom in a molecule and describes the connectivity of atoms within the molecule

synapse – the connection between two neurons; neurotransmitters are released from the terminal into the synaptic space and bind to receptors on the neighboring neuron.

tolerance – a drug (e.g., alcohol) produces a smaller effect at the same dose that originally produced a larger effect

transcription – the passage of information from DNA to mRNA in the nucleus; this is directed by several enzymes.

translation – the process of assembling a specific sequence of amino acids (based on the instructional code provided by the mRNA) to form a protein. It occurs in the cytoplasm on ribosomes or in the rough endoplasmic reticulum.

van der Waals forces – weakly attractive forces between neutral atoms or groups on molecules (e.g. hydrogen bonds, dipole-dipole and dispersion forces)

vaporization – when a compound in a liquid becomes a gas

volatile – the ability of a compound to move from a liquid to gas phase; the fewer the hydrogen bonds the more volatile the substance