UNIT 1

nature–nurture issue

the longstanding controversy over the relative contributions that genes and experience make to the development of psychological traits and behaviors. Today’s science views traits and behaviors as arising from the interaction of nature and nurture.

natural selection

the principle that the inherited traits enabling 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.

evolutionary psychology.

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

behavior genetics.

the study of the relative power and limits of genetic and environmental influences on behavior.

mutations

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

environment

every nongenetic influence, from prenatal nutrition to our experiences of the people and things around us.

heredity

the genetic transfer of characteristics from parents to offspring.

Genes

the biochemical units of heredity.

genome

the complete instructions for making an organism

Identical (monozygotic) twins

individuals who developed from a single fertilized egg that split in two, creating two genetically identical organisms.

Fraternal (dizygotic) twins

individuals who developed from separate fertilized eggs. They are genetically no closer than ordinary siblings, but they share a prenatal environment.

interact.

the interplay that occurs when the effect of one factor (such as environment) depends on another factor (such as heredity).

Epigenetics

“above” or “in addition to” (epi) genetics; the study of the molecular mechanisms by which environments can influence genetic expression (without a DNA change).

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 sensory organs.

Sensory neurons

neurons that carry incoming information from the body’s tissues and sensory receptors to the brain and spinal cord.

Motor 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.

reflexes

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

neurons

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.

dendrite

a neuron’s often bushy, branching extensions that receive and integrate messages, conducting impulses toward the cell body.

axon

the segmented 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; it enables vastly greater transmission speed as neural impulses hop from one node to the next.

glial cells

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

[en-DOR-fins] “morphine within” — natural, opioid-like neurotransmitters linked to pain control and to pleasure.

Agonist

a molecule that increases a neurotransmitter’s action.

Antagonists

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

endocrine system

the body’s “slow” chemical communication system; a set of glands and fat tissue that secrete hormones into the bloodstream.

hormones

chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues.

psychoactive drugs

a chemical substance that alters the brain, causing changes in perceptions and moods.

substance use disorder

a disorder characterized by continued substance use despite significant life disruption.

Depressants

drugs that reduce neural activity and slow body functions.

barbiturate

drugs that depress central nervous system activity, reducing anxiety but impairing memory and judgment.

opioids

opium and its derivatives; they depress neural activity, temporarily lessening pain and anxiety.

Stimulants

drugs that excite neural activity and speed up body functions.

Hallucinogens

psychedelic (“mind-manifesting”) drugs that distort perceptions and evoke sensory images in the absence of sensory input.

near-death experience

an altered state of consciousness reported after a close brush with death (such as cardiac arrest); often similar to drug-induced hallucinations.

Biological psychologists

the scientific study of the links between biological (genetic, neural, hormonal) and psychological processes. (Some biological psychologists call themselves behavioral neuroscientists, neuropsychologists, behavior geneticists, physiological psychologists, or biopsychologists.)

biopsychosocial approach

an integrated approach that incorporates biological, psychological, and social-cultural levels of analysis.

levels of analysis

the differing complementary views, from biological to psychological to social-cultural, for analyzing any given phenomenon.

neuroplasticity.

the brain’s ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience.

lesion

[LEE-zhuhn] tissue destruction. Brain lesions may occur naturally (from disease or trauma), during surgery, or experimentally (using electrodes to destroy brain cells).

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.

PET (positron emission tomography)

technique for detecting brain activity that displays 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. 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.

hindbrain

consists of the medulla, pons, and cerebellum; directs essential survival functions, such as breathing, sleeping, and wakefulness, as well as coordination and balance.

midbrain

found atop the brainstem; connects the hindbrain with the forebrain, controls some motor movement, and transmits auditory and visual information.

forebrain

consists of the cerebral cortex, thalamus, and hypothalamus; manages complex cognitive activities, sensory and associative functions, and voluntary motor activities.

brainstem

the central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions.