Unit 1: Biological Bases of Behavior

neuron

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

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.

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

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

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 into 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).

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 arc

A relatively direct connection between a sensory neuron and a motor neuron that allows an extremely rapid response to a stimulus, often without conscious brain involvement.

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.

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.

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 computer-generated images of soft tissue and show brain anatomy.

fMRI (functional MRI)

a technique for revealing bloodflow and, therefore, brain activity by comparing successive scans of soft tissue; shows 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; 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 activating system

Located in the upper brain stem; responsible for maintenance of consciousness, specifically one's level of 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 emotions, particularly aggression and fear

hypothalamus

a neural structure lying below 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 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 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

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

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 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.

genes

the biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing proteins. (Myers Psychology for AP 3e p. 130)

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)

evolutionary psychology

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

sleep

periodic, natural loss of consciousness--as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation

circadian rhythm

the 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.

NREM sleep

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

alpha waves

the relatively slow brain waves of a relaxed, awake state

delta waves

the large, slow brain waves associated with deep sleep

hypnagogic sensations

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

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

REM sleep behavior disorder

a neurological disorder in which the person does not become paralyzed during REM sleep and thus acts out dreams

dream

a sequence of images, emotions, and thoughts passing through a sleeping person's mind.

information processing theory

theory that dreams help us sort out the day's events and consolidate our memories

activation-synthesis theory

a theory of dreaming; this theory proposes that the brain tries to make sense of random brain activity that occurs during sleep by synthesizing the activity with stored memories

sensation

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment

bottom-up processing

information processing that begins with the sensory receptors and works up to the brain's integration of sensory information

top-down processing

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations

transduction

conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret.

absolute threshold

the minimum stimulation needed to detect a particular stimulus 50 percent of the time

signal detection theory

a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and alertness.

Priming

the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response

difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time; also known as just-noticeable difference

Weber's Law

the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

Wavelength

the distance from the peak of one light or sound wave to the peak of the next.

hue

the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth

Intensity

the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude

Cornea

The clear tissue that covers the front of the eye