BBB

cell body

the part of a neuron that contains the nucleus; the cell’s life-support center.

dendrites

a neuron’s often bushy, branching extensions that receive and integrate

messages, conducting impulses toward the cell body.

axon

the neuron extension that passes messages through its branches to other neurons

or to muscles or glands.

neuron a nerve cell; the basic building block of the nervous system.

myelin sheath

a fatty tissue layer segmentally encasing the axons of some neurons; enables

vastly greater transmission speed as neural impulses hop from one node to the

next.

glial cells (glia)

cells in the nervous system that support, nourish, and protect neurons; they also

play a role in learning, thinking, and memory.

action potential

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

threshold

the level of stimulation required to trigger a neural impulse.

refractory period

in neural processing, a brief resting pause that occurs after a neuron has fired;

subsequent action potentials cannot occur until the axon returns to its resting

state.

all-or-none response

a neuron’s reaction of either firing (with a full-strength response) or not firing.

synapse [SIN-aps]

the junction between the axon tip of the sending neuron and the dendrite or cell

body of the receiving neuron. The tiny gap at this junction is called the synaptic

gap or synaptic cleft.

neurotransmitters

chemical messengers that cross the synaptic gaps between neurons. When

released by the sending neuron, neurotransmitters travel across the synapse and

bind to receptor sites on the receiving neuron, thereby influencing whether that

neuron will generate a neural impulse.

reuptake

a neurotransmitter’s reabsorption by the sending neuron

endorphins

“morphine within”—natural, opiate-like neurotransmitters linked to pain

control and to pleasure.

agonist

a molecule that increases a neurotransmitter’s action.

antagonist

a molecule that inhibits or blocks a neurotransmitter’s action.

nervous system

the body’s speedy, electrochemical communication network, consisting of all

the nerve cells of the peripheral and central nervous systems.

central nervous system (CNS)

the brain and spinal cord.

peripheral nervous system (PNS)

the sensory and motor neurons that connect the central nervous system (CNS)

to the rest of the body.

nerves

bundled axons that form neural cables connecting the central nervous system

with muscles, glands, and sense organs.

sensory (afferent) neurons

neurons that carry incoming information from the body’s tissues and sensory

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receptors to the brain and spinal cord.

motor (efferent) neurons

neurons that carry outgoing information from the brain and spinal cord to the

muscles and glands.

interneurons

neurons within the brain and spinal cord; they communicate internally and

process information between the sensory inputs and motor outputs.

somatic nervous system

the division of the peripheral nervous system that controls the body’s skeletal

muscles. Also called the skeletal nervous system.

autonomic nervous system (ANS)

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 nervous system

the division of the autonomic nervous system that arouses the body, mobilizing

its energy.

parasympathetic nervous system

the division of the autonomic nervous system that calms the body, conserving

its energy.

reflex

a simple, automatic response to a sensory stimulus, such as the knee-jerk

response.

endocrine system

the body’s “slow” chemical communication system; a set of glands that secrete

hormones into the bloodstream.

hormones

chemical messengers that are manufactured by the endocrine glands, travel

through the bloodstream, and affect other tissues.

adrenal [ah-DREEN-el] glands

a pair of endocrine glands that sit just above the kidneys and secrete hormones

(epinephrine and norepinephrine) that help arouse the body in times of stress.

pituitary gland

the endocrine system’s most influential gland. Under the influence of the

hypothalamus, the pituitary regulates growth and controls other endocrine

glands.

lesion [LEE-zhuhn]

tissue destruction. A brain lesion is a naturally or experimentally caused

destruction of brain tissue.

EEG (electroencephalogram)

an amplified recording of the waves of electrical activity sweeping across the

brain’s surface. These waves are measured by electrodes placed on the scalp

MEG (magnetoencephalography)

a brain imaging technique that measures magnetic fields from the brain’s

natural electrical activity.

CT (computed tomography) scan

a series of X-ray photographs taken from different angles and combined by

computer into a composite representation of a slice of the brain’s structure.

(Also called CAT scan.)

PET (positron emission tomography) scan

a visual display of brain activity that detects where a radioactive form of

glucose goes while the brain performs a given task.

MRI (magnetic resonance imaging)

a technique that uses magnetic fields and radio waves to produce computergenerated images of soft tissue. MRI scans show brain anatomy.

fMRI (functional MRI)

a technique for revealing bloodflow and, therefore, brain activity by comparing

successive MRI scans. fMRI scans show brain function as well as structure.

brainstem

the oldest part and central core of the brain, beginning where the spinal cord

swells as it enters the skull; the brainstem is responsible for automatic survival

functions.

medulla [muh-DUL-uh]

the base of the brainstem; controls heartbeat and breathing.

thalamus [THAL-uh-muss]

the brain’s sensory control center, located on top of the brainstem; it directs

messages to the sensory receiving areas in the cortex and transmits replies to

the cerebellum and medulla.

reticular formation

a nerve network that travels through the brainstem into the thalamus and plays

an important role in controlling arousal.

cerebellum [sehr-uh-BELL-um]

the “little brain” at the rear of the brainstem; functions include processing

sensory input, coordinating movement output and balance, and enabling

nonverbal learning and memory.

limbic system

neural system (including the amygdala, hypothalamus, and hippocampus)

located below the cerebral hemispheres; associated with emotions and drives.

amygdala [uh-MIG-duh-la]

two lima-bean-sized neural clusters in the limbic system; linked to emotion.

hypothalamus [hi-po-THAL-uh-muss]

a neural structure lying below (hypo) the thalamus; it directs several

maintenance activities (eating, drinking, body temperature), helps govern the

endocrine system via the pituitary gland, and is linked to emotion and reward.

hippocampus

a neural center located in the limbic system; helps process for storage explicit

(conscious) memories of facts and events.

cerebral [seh-REE-bruhl] cortex

the intricate fabric of interconnected neural cells covering the cerebral

hemispheres; the body’s ultimate control and information-processing center.

frontal lobes

the portion of the cerebral cortex lying just behind the forehead; involved in

speaking and muscle movements and in making plans and judgments.

parietal [puh-RYE-uh-tuhl] lobes

the portion of the cerebral cortex lying at the top of the head and toward the

rear; receives sensory input for touch and body position.

occipital [ahk-SIP-uh-tuhl] lobes

the portion of the cerebral cortex lying at the back of the head; includes areas

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that receive information from the visual fields.

temporal lobes

the portion of the cerebral cortex lying roughly above the ears; includes the

auditory areas, each receiving information primarily from the opposite ear.

motor cortex

an area at the rear of the frontal lobes that controls voluntary movements.

somatosensory cortex

an area at the front of the parietal lobes that registers and processes body touch

and movement sensations.

association areas

areas of the cerebral cortex that are not involved in primary motor or sensory

functions; rather, they are involved in higher mental functions such as learning,

remembering, thinking, and speaking.

plasticity

the brain’s ability to change, especially during childhood, by reorganizing after

damage or by building new pathways based on experience.

neurogenesis

the formation of new neurons.

corpus callosum [KOR-pus kah-LOW-sum]

the large band of neural fibers connecting the two brain hemispheres and

carrying messages between them.

split brain

a condition resulting from surgery that isolates the brain’s two hemispheres by

cutting the fibers (mainly those of the corpus callosum) connecting them.

consciousness

our subjective awareness of ourselves and our environment.

cognitive neuroscience

the interdisciplinary study of the brain activity linked with cognition (including

perception, thinking, memory, and language).

dual processing

the principle that information is often simultaneously processed on separate

conscious and unconscious tracks.

blindsight

a condition in which a person can respond to a visual stimulus without

consciously experiencing it.

parallel processing

processing many aspects of a problem simultaneously; generally used to

process well-learned information or to solve easy problems.

sequential processing

processing one aspect of a problem at a time; generally used to process new

information or to solve difficult problems.

behavior genetics

the study of the relative power and limits of genetic and environmental

influences on behavior.

heredity

the genetic transfer of characteristics from parents to offspring.

environment

every nongenetic influence, from prenatal nutrition to the people and things

around us.

chromosomes

threadlike structures made of DNA molecules that contain the genes.

DNA (deoxyribonucleic acid)

a complex molecule containing the genetic information that makes up the

chromosomes.

genes

the biochemical units of heredity that make up the chromosomes; segments of

DNA capable of synthesizing proteins.

genome

the complete instructions for making an organism, consisting of all the genetic

material in that organism’s chromosomes.

identical (monozygotic) twins

develop from a single fertilized egg that splits in two, creating two genetically

identical organisms.

fraternal (dizygotic) twins

develop from separate fertilized eggs. They are genetically no closer than

ordinary brothers and sisters, but they share a prenatal environment.

heritability

the proportion of variation among individuals in a group that we can attribute to

genes. The heritability of a trait may vary, depending on the range of

populations and environments studied.

interaction

the interplay that occurs when the effect of one factor (such as environment)

depends on another factor (such as heredity).

molecular genetics

the subfield of biology that studies the molecular structure and function of

genes.

molecular behavior genetics

the study of how the structure and function of genes interact with our

environment to influence behavior.

epigenetics

“above” or “in addition to” (epi) genetics; the study of environmental

influences on gene expression that occur without a DNA change.

evolutionary psychology

the study of the evolution of behavior and the mind, using principles of natural

selection.

natural selection

the principle that inherited traits that better enable an organism to survive and

reproduce in a particular environment will (in competition with other trait

variations) most likely be passed on to succeeding generations.

mutation a random error in gene replication that leads to a change.

social script a culturally modeled guide for how to act in various situations.