agonist: a chemical/substance that activates a specific type of receptor site in the brain or body (opposite of antagonist).
alleles: the alternative forms of a gene found at a specific chromosomal location.
amygdala: location in the brain associated with emotion.
anhedonia: inability to experience pleasure/happiness.
antagonists: substances that block or reduce responses by blocking receptors (opposite of agonist)
autonomic nervous system (ANS): portions of the nervous system responsible for controlling bodily functions outside of conscious control (e.g., digestion, heart rate, breathing rate, blood pressure).
central nervous system (CNS): the brain and spinal cord.
chromosomes: sites where genes are located; humans have 23 pairs of chromosomes present in every cell, except egg and sperm cells which have 23 single chromosomes
chromosomal regions: sections of a chromosome.
concordance: the degree of similarity or agreement in what is being compared (e.g., a pair of twins).
dizygotic twins: twins developing from two different fertilized eggs.
DNA: the hereditary material (deoxyribonucleic acid) passed from parents to offspring.
dopamine: a primary neurotransmitter (and precursor to producing other molecules, like epinephrine)
downregulation: reducing or suppressing a response or sensitivity to a substance (opposite of upregulation).
dysphoria: experience of unease or dissatisfaction with life which can be intense.
endorphins & enkaphalins: peptides in the body with brain and nervous system effects, especially with regard to opiate receptors and pain control.
epinephrine: also known as adrenaline, a stimulant/arousing hormone released in the body that influences autonomic nervous system functions (heart rate, respiration, and muscle preparation for action), acts in opposition to norepinephrine (noradrenaline).
excitatory neurotransmitters: neurotransmitters that have an activating effect on postsynaptic neurons.
GABA (gamma-aminobutyric acid):a neurotransmitter pervasive throughout the brain which inhibits neuron responses.
genes: sections of DNA sequences that direct how/whether biological processes occur.
genome: the complete set of genes present in a cell/organism; humans share 99.9% of their genome, with individual difference attributed to that very small remaining percent (NHGRI, 2018)
genotype: the set of genes responsible for a certain trait/characteristic.
glial cells: a type of cell in the CNS that support neurons.
glutamate: an excitatory neurotransmitter.
half-life: the period of time it takes for the body to metabolize a drug by half its concentration.
heritability: estimate or measure of the contribution of genes (versus environment) to a phenotypic outcome based on a proportion of observed variance in the trait studied
hippocampus: area of the brain responsible for emotion, memory, and control of the autonomic nervous system.
homeostasis: the tendency in systems to establish and maintain a relatively stable, balanced state; many physiological processes have opposites so they can work in tandem to create this balance.
inhibitory neurotransmitters: neurotransmitters that have a suppressing effect on postsynaptic neurons.
limbic system:a networked system of brain regions that control basic emotions and drives.
metabolites: substances formed in the process of breaking down (metabolizing) other substances.
monozygotic twins: twins developing out of the same egg fertilized by a single sperm.
neuroanatomy: study of the anatomy (structures) of the nervous system.
neurochemistry: study of the biochemical processes occurring in the nervous system.
neurons: type of cell in the CNS (nerve cells).
neurotransmitters: types of molecules involved in communication between neurons.
norepinephrine: also known as noradrenaline, a suppressing/inhibitory hormone released in the body that influences autonomic nervous system functions (heart rate, respiration, and muscle preparation for action), acts in opposition to epinephrine (adrenaline).
nucleus accumbens: also called the accumbens nucleus, an area of the brain involved in the reward circuit, primarily using dopamine to stimulate desire and serotonin to establish satiation.
pharmacokinetics: branch of pharmacology concerned with how drugs move and are metabolized in the body.
pharmacotherapy: providing treatment by the use of medications/drugs.
phenotype: an observable/expressed characteristic, trait, behavior, or disease outcome influenced by some combination of genotype and environment.
polygenic: a trait, characteristic, or disease attributable to variation in multiple genes.
postsynaptic neuron: a neuron receiving communication from another neuron.
prefrontal cortex: area of the brain playing a significant role in regulating cognitive processes and higher-order thought, emotion, and behavior.
presynaptic neuron: a neuron sending communication to another neuron.
psychopharmacology: the study and use of psychoactive/psychotropic medications, drugs, or other substances to create brain changes.
receptors: sites on (nerve) cells where neurotransmitters have their influence if there is a match between type of neurotransmitter and receptor site.
serotonin: a neurotransmitter involved in balancing emotion and mood, with a role in social behavior, sleep, memory, appetite, and sexual function.
synapse/synaptic cleft: the space between two neurons where communication by neurotransmitters takes place.
synergism: the increase in strength or duration of an effect by combining two substances with similar actions.
transporters: the route by which neurotransmitter molecules are returned to the presynaptic neuron vesicles.
upregulation: enhancing or increasing a response or sensitivity to a substance (opposite of downregulation).