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inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment

Critical Period

a specific time in development when certain skills or abilities are most easily learned


ability of an organism to survive and reproduce in its environment.


Individual cells in the nervous system that receive, integrate, and transmit information


The cell body of a neuron.


Branchlike parts of a neuron that are specialized to receive information.


long fiber that carries impulses away from the cell body of a neuron

Mylein Sheath

a layer of fatty tissue segmentally encasing the fibers of many neurons enables vastly greater transmission speed of neural impulses

Terminal Buttons

Small knobs at the end of axons that secrete chemicals called neurotransmitters


The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron.

Resting Potential

the stable, negative electrical charge across the cell membrane of a resting neuron

Action Potential

A neural impulse; a brief electrical charge that travels down an axon.

Absolute Refractory Period

minimum length of time after an action potential during which another action potential cannot begin

Synaptic Cleft

space between two connecting neurons where neurotransmitters are released


chemical messengers that traverse the synaptic gaps between neurons

Post-synaptic Potential (PSP)

a voltage change in a receptor cite of a neuron

Excitatory PSP

An electric potential that increases the likelihood that a postsynaptic neuron will fire action potentials.

Inhibitory PSP

An electric potential that decreases the likelihood that a postsynaptic neuron will fire action potentials.

Family Studies

researchers assess hereditary influence by examining blood relatives to see how much they resemble one another on a specific trait


A chemical that mimics the action of a neurotransmitter


A chemical that opposes the action of a neurotransmitter


An entire family of internally produced chemicals that resemble opiates in structure and effects

Peripheral Nervous System

System that includes all those nerves that lie outside the brain and spinal chord


Bundles of neuron fibers (axons) that travel together in the peripheral nervous system

Somatic Nervous System

The part of the peripheral nervous system that controls voluntary movement of skeletal muscles

Afferent Nerve Fibers

Axons that carry information inward to the central nervous system from the periphery of the body

Efferent Nerve Fibers

Axons that carry information outward from the central nervous system to the periphery of the body.

Autonomic Nervous System

The part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

Sympathetic Division

The branch of the autonomic nervous system that mobilizes the body's resources for emergencies.


the branch of the nervous system that automatically calms us down when the reason for arousal has passed

Central Nervous System (CNS)

System that consists of the brain and spinal cord

Cerebral Fluid (CSF)

A solution that fills the hollow cavities of the brain and circulates around the brain and spinal cord. Provides nourishment, cushions, and removes wastes.


device used to record the electrical activity of the brain

Twin Studies

studies of identical and fraternal twins to determine the relative influence of heredity and environment on human behavior


Procedure involves inserting an electrode into a brain structure and passing a high-frequency current through it to burn the tissue and disable the structure

Electric Stimulation of the Brain

Method that involves sending a weak electric current into a brain structure to stimulate (activate) it.

Hind brain

part of the brain between the spinal cord and the midbrain, consisting of the pons, medulla, and cerebellum

Mid brain

between the hind and forebrain it deals with vision, hearing and other senses


top of the brain which includes the thalamus, hypothalamus, and cerebral cortex; responsible for emotional regulation, complex thought, memory aspect of personality; largest and most complex region


the structure of the brain that relays messages from the sense organs to the cerebral cortex (except smell)


a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion

Limbic System

A group of neural structures at the base of the cerebral hemispheres that is associated with emotion and motivation

Cerebral Cortex

the intricate fabric of interconnected neural cells that covers the cerebellum; the body's ultimate control and information-processing center

Cerebral Hemispheres

the right and left halves of the cerebellum

Corpus Callosum

the large band of neural fibers connecting the two brain hemispheres and carrying messages between them

Adoption Studies

research carried out on children, adopted at birth by parents not related to them, to determine the relative influence of heredity and environment on human behavior


a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them

Endocrine System

System of glands that secrete chemicals into the bloodstream that help control bodily functioning


The chemical substances released by the endocrine system

Pituitary Gland

The "master gland" of the endocrine system


Threadlike strands of DNA molecules that carry genetic information


A one-celled organism formed by the union of a sperm and an egg


DNA segments that serve as the key functional units in hereditary transmission

Dominant Gene

A gene that is expressed when the paired genes are different

Recessive Gene

A gene that is masked when paired genes are different


A person's genetic make-up


the way in which a persons genotype is manifested in observable characteristics

Polygenic Traits

Characteristics that are influences by more than one pair of genes

Inclusive Traits

The sum of an individuals own reproductive success, plus the effects the organism has on the reproductive success of related others


A mating system in which one male and one female mate exclusively, or almost exclusively, with one another

Perceptual Asymetrics

An inter disciplinary field that studies the influence of genetic factors on behavioral traits


The two genes in a specific pair are the same


the two genes in a specific pair are different

Identical Twins

twins who develop from a single fertilized egg that splits in two, creating two genetically identical organisms

Fraternal Twins

twins who develop from separate fertilized eggs. They are genetically no closer than brothers and sisters, but they share a fetal environment.

Genetic Mapping

The process of determining the location and chemical sequence of specific genes on specific chromosomes

Natural Selection

process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest

Parental Investment

What each sex invests-in terms of time, energy, survival risks, and forgone opportunities-to produce and nurture offspring.


mating system in which females have more than one male


mating system in which males have more than one female


A process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane

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