Biological Bases of Behavior

Neuron

Basic building block of the nervous system

Cell Body

Part of a neuron that contains the nucleus; the cell's life-support center

Dendrites

Neuron's often bushy, branching extensions that receive and integrate messages, conducting impulses toward the cell body

Axon

Neuron extension that passes messages through its branches to other neurons or to muscles or glands

Myelin Sheath

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 (Glue Cells)

Cells in the nervous system that support, nourish, and protect neurons; they also play a role in learning, thinking, and memory

Action Potential

Neural impulse; a brief electrical charge that travels down an axon

Threshold

The level of stimulation required to trigger a neural impulse

Refractory Period

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 firin

Synapse

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 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 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

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 t echnique that uses magnetic fields and radio waves to produce computer-generated images of soft tissue. MRI scans show brain anatomy

fMRI (functional MRI)

A technique for revealing blood flow 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

The base of the brainstem; controls heartbeat and breathing

Thalamus

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

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

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

Hypothalamus

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 Cortex

The outer surface of the brain, is associated with higher level processes such as consciousness, thought, emotion, reasoning, language, and memory. The four lobes in the cortex are the frontal lobe, parietal lobe, temporal lobe, occipital lobe

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 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 Lobes

portion of the cerebral cortex lying at the back of the head; includes areas that receive information from the VISUAL fields (eyes)

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; the brain's natural mode of information processing for many functions

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.

Consciousness

our subjective awareness of ourselves and our environment

Hypnosis

a social interaction in which one person (the hypnotist) suggests to another (the subject) that certain perceptions, feelings, thoughts, or behaviors will spontaneously occur

Posthypnotic Suggestion

a suggestion, made during a hypnosis session, to be carried out after the subject is no longer hypnotized; used by some clinicians to help control undesired symptoms and behaviors

Dissociation

a split in consciousness, which allows some thoughts and behaviors to occur simultaneously with others

Sleep

a periodic, natural loss of consciousness — as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation. (Adapted from Dement, 1999.)

Circadian Rhythm

our biological clock; regular bodily rhythms (for example, of temperature and wakefulness) that occur on a 24-hour cycle

REM Sleep

rapid eye movement sleep; a recurring sleep stage during which vivid dreams commonly occur. Also known as paradoxical sleep, because the muscles are relaxed (except for minor twitches) but other body systems are active

Alpha Waves

the relatively slow brain waves of a relaxed, awake state

NREM sleep

non-rapid eye movement sleep; encompasses all sleep stages except for REM sleep

Hallucinations

false sensory experiences, such as seeing something in the absence of an external visual stimulus

Hypnagogic Sensations

bizarre experiences, such as jerking or a feeling of falling or floating weightlessly, while transitioning to sleep

Delta Waves

the large, slow brain waves associated with the deep sleep of NREM-3

Suprachiasmatic Nucleus (SCN)

a pair of cell clusters in the hypothalamus that controls circadian rhythm. In response to light, the SCN causes the pineal gland to adjust melatonin production, thus modifying our feelings of sleepiness

Insomnia

recurring problems in falling or staying asleep

Narcolepsy

a sleep disorder characterized by uncontrollable sleep attacks. The sufferer may lapse directly into REM sleep, often at inopportune times

Sleep Apnea

a sleep disorder characterized by temporary cessations of breathing during sleep and repeated momentary awakenings

Night Terrors

a sleep disorder characterized by high arousal and an appearance of being terrified; unlike nightmares, night terrors occur during NREM-3 sleep, within two or three hours of falling asleep, and are seldom remembered