UNIT 3

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 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 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 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

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.

Neurotransmitters

Chemical messengers that cross the synaptic gaps between neurons, influencing whether the receiving neuron will generate a neural impulse.

Reuptake

A neurotransmitter’s reabsorption by the sending neuron.

Endorphins

Natural, opiate-like neurotransmitters linked to pain control and pleasure.

Agonist

A molecule that increases a neurotransmitter's actions.

Antagonists

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 nervous system.

Central nervous system

The brain and spinal cord.

Peripheral nervous system

The sensory and motor neurons that connect the central nervous system 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 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 that communicate internally and process information between sensory inputs and motor outputs.

Somatic nervous system

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

Autonomic nervous system

The part of the peripheral nervous system that controls the glands and the muscles of the internal organs.

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.

Endocrine system

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

Hormones

Chemical messengers manufactured by the endocrine glands that travel through the bloodstream and affect other tissues.

Adrenal glands

Endocrine glands that sit above the kidneys and secrete hormones that help arouse the body in times of stress.

Pituitary gland

The endocrine system’s most influential gland, regulating growth and controlling 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.

MEG (magnetoencephalography)

A brain imaging technique that measures magnetic fields from the brain's natural electrical activity.

CT

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

A visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task.

Brainstem

The oldest part and central core of the brain, responsible for automatic survival functions.

Medulla

The base of the brainstem; controls heartbeat and breathing.

Thalamus

The brain’s sensory control center, directing messages to sensory receiving areas in the cortex.

Reticular formation

A nerve network that travels through the brainstem into the thalamus, playing an important role in controlling arousal.

Cerebellum

the liittle brain at the rear of the brainsteml functions include processing senroy input, coordinating movement output and balance, and enabling nonverbal learning and memory

Limbic system

neural system (including the amygdala, hypothalamus) 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 the thalamus; it directs several maintenance activities, 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 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

Frontol lobes

the portion of the cerebral cortex lying just behind the forehead; involved in speaking and muscle movements and in making plans and judgments

Pareital 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 rcortex

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

Somatosensory cortex

an area at the font 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 brains

a condition resulting from surgery that isolates the brain's two hemispheres by cutting the fibers connecting them

Consciouness

our subjective awareness of ourselves and our environment

Cognitive neuroscience

the interdisciplinary study of the brain activity linked with cognition

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 geneticists

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

Chromosome

threadlike structures made of DNA molecules that contain the genes

DNA

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

Interact

the interplay that occurs when the effect of one factor depends on another factor

Molecular behavior genetics

 the study of how the structure and function of genes interact with our environment to influence behavior

Molecular genetics

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

Epigentics

above or in addition to genetics; the study of environmental influences in gene expression that occur without a DNA change

Evolutionary psychologists

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

Natural selection

the principles that inherited traits that better enable an organism to survive and reproduce in a particular environment will most likely be passed on to succeeding generations

Mutations

a random error in gene replication that leads to a change

Social script

a culturally modeled guide for how to act in various situations