Chapter 2

neuroplasticity

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

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 segmented neuron extension that passes messages through its branches to other neurons or to muscles or glands.

Myelin

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 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

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 gap 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 sensory 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 reflex.

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.

adrenal glands

a pair of endocrine glands that sits just above the kidneys and secretes 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. Brain lesions occur naturally (disease or trauma), in 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.

PET (positron emission tomography)

a 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.

medulla

the hindbrain structure that is the brainstem’s base; controls heartbeat and breathing.

thalamus

the forebrain’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; filters information and plays an important role in controlling arousal.

cerebellum

the hindbrain’s “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 located mostly in the forebrain-below the cerebral hemispheres-that includes the amygdala, hypothalamus, and hippocampus; associated with emotions and drives.

amygdala

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

hypothalamus

a limbic system 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 in the limbic system that helps process explicit (conscious) memories-of facts and events-for storage.

cerebral cortex

the intricate fabric of interconnected neural cells covering the forebrain’s 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

a cerebral cortex area at the rear of the frontal lobes that controls voluntary movements.

somatosensory cortex

a cerebral cortex 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.

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 separates the brain’s two hemispheres by cutting the fibers (mainly those of the corpus callosum) connecting them.

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.

behavior genetics

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

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; small 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

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 shared a prenatal environment.

interaction

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).

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 subsequent generations.

mutation

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