Chapter 3: Biology and Behavior

Neurons

The basic units of the nervous system; cells that receive, integrate and transmit information in the nervous system. They operate through electrical impulses and communicate through chemical signals.

Central Nervous System (CNS)

The brain and spinal cord.

Peripheral Nervous System (PNS)

All nerve cells in the body that are not part of the central nervous system. Includes the somatic and autonomic nervous systems.

Sensory Neurons

One of the three types of neurons; these neurons detect information from the physical world and pass that information to the brain.

Motor Neurons

One of the three types of neurons; direct muscles to contract or relax, thereby producing movement.

Interneurons

One of the three types of neurons; communicate within local or short-distance circuits.

Dendrites

Branchlike extensions of the neuron that detect information from other neurons.

Cell Body

The site in the neuron where information from thousands of other neurons is collected and integrated.

Axon

A long narrow outgrowth of a neuron by which information (electrical signal) is transmitted to other neurons through terminal buttons.

Terminal Buttons

At the ends of axons, small nodules that release chemical signals from the neuron into the synapse.

Synapse

The gap between the axon of a "sending" neuron and the dendrites of the "receiving" neuron; the site at which chemical communication occurs between neurons.

Resting Membrane Potential

The electrical charge of a neuron when it is not active.

Action Potential

The electrical signal that passes along the axon and subsequently causes the release of chemicals from the terminal buttons.

Myelin Sheath

A fatty material, made up of glial cells, that insulates some axons to allow for faster movement of electrical impulses along the axon.

Nodes of Ranvier

Small gaps of exposed axon, between the segments of myelin sheaths, where action potentials take place.

All-or-None Principle

The principle that when a neuron fires, it fires with the same potency each time; a neuron either fires or it does not.

Neurotransmitters

Chemical substances that transmit signals from one neuron to another.

Receptors

In neurons, specialized protein molecules on the postsynaptic membrane; neurotransmitters bind to these molecules after passing across the synapse.

Reuptake

The process whereby a neurotransmitter is taken back into the presynaptic terminal buttons, thereby stopping its activity.

Acetylcholine (aCh)

The neurotransmitter responsible for motor control at the junction between nerves and muscles; also involved in mental processes such as learning, memory, sleeping, dreaming.

Epinephrine

A monoamine neurotransmitter responsible for burst of energy after an event that is exciting or threatening.

Norepinephrine

A monoamine neurotransmitter involved in states of arousal and attention.

Serotonin

A monoamine neurotransmitter important for a wide range of psychological activity, including emotional states, impulse control, and dreaming.

Dopamine

A monoamine neurotransmitter involved in motivation, reward, and motor control over voluntary movement (depletion can lead to Parkinson's).

GABA

The primary inhibitory transmitter in the nervous system.

Glutamate

The primary excitatory transmitter in the nervous system.

Endorphins

Neurotransmitters involved in natural pain reduction and reward.

Broca's Area

A small portion of the left frontal region of the brain, crucial for the production of language.

EEG

A device that measures electrical activity in the brain.

PET

A method of brain imaging that assesses metabolic activity by using a radioactive substance injected into the bloodstream.

MRI

A method of brain imaging that uses a powerful magnetic field to produce high-quality images of the brain.

fMRI

An imaging technique used to examine changes in the activity of the working human brain by measuring changes in the blood's oxygen levels.

TMS

The use of strong magnets to briefly interrupt normal brain activity as a way to study brain regions.

Brain Stem

An extension of the spinal cord; it houses structures that control functions associated with survival, such as heart rate, breathing, swallowing, vomiting, urinating, orgasm.

Cerebellum

A large, convoluted protuberance at the back of the brain stem; it is essential for coordinated movement and balance.

Thalamus

The gateway to the brain; it receives almost all incoming sensory information before the information reaches the cortex.

Hypothalamus

Brain structure that is involved in the regulation of bodily functions, including body temperatures, body rhythms, blood pleasure, and blood glucose levels; also influences basic motivated behaviors.

Hippocampus

Brain structure that is associated with the formation of memories.

Amygdala

Brain structure that serves a vital role in learning to associate things with emotional responses and in processing emotional information.

Basal Ganglia

A system of subcortical structures that are important for the planning and production of movement.

Cerebral Cortex

The outer layer of brain tissue, which forms the convoluted surface of the brain; the site of all thoughts, perceptions, and complex behaviors.

Corpus Callosum

Massive bridge of millions of axons that connects the hemispheres and allows information to flow between them.

Occipital Lobes

Regions of the cerebral cortex - at the back of the brain - important for vision.

Parietal Lobes

Regions of the cerebral cortex important for the sense of touch and for attention to the environment.

Temporal Lobes

Regions of the cerebral cortex important for processing auditory information, for memory, and for object and face perception.

Frontal Lobes

Regions of the cerebral cortex important for movement and higher-level psychological processes associated with the prefrontal cortex.

Prefrontal Cortex

The foremost portion of the frontal lobes, especially prominent in humans; important for attention, working, memory, decision making, appropriate social behavior, personality.

Split Brain

A condition that occurs when the corpus callosum is surgically cut and the two hemispheres of the brain do not receive information directly from each other.

Somatic Nervous System (SNS)

A component of the peripheral nervous system; it transmits sensory signals and motor signals between the central nervous system and the skin, muscles, joints.

Autonomic Nervous System (ANS)

A component of the peripheral nervous system; it transmits sensory signals and motor signals between the central nervous system and the body's glands and internal organs (regulates internal environment).

Sympathetic Division

Division of the autonomic nervous system; it prepares the body for action.

Parasympathetic Division

Division of the autonomic nervous system; it returns the body to its resting state.

Endocrine System

A communication system that uses hormones to influence thoughts, behaviors, and actions.

Hormones

Chemical substances, released from endocrine glands, that travel through the bloodstream to targeted tissues; the tissues are subsequently influenced by these chemical substances.

Gonads

The main endocrine glands involved in sexual behavior: in males, the testes; in females, the ovaries.

Pituitary Gland

A gland located at the base of the hypothalamus; it sends hormonal signals to other endocrine glands, controlling their release of hormones.

Plasticity

A property of the brain that allows it to change as a result of experience or injury.

Gene Expression

Whether a particular gene is turned on or off.

Chromosomes

Structures within the cell body that are made up of DNA, segments of which comprise individual genes.

Genes

The units of heredity that help determine the characteristics of an organism.

Genotype

The genetic constitution of an organism, determined at the moment of conception.

Phenotype

Observable physical characteristics, which result from both genetic and environmental influences.

Heritability

A statistical estimate of the extent to which variation in a trait within a population is due to genetics.

Inhibitory Signal

Signal that increases negative charge and polarization.

Excitatory Signals

Signal that decreases negative charge and polarization; leads to action potential firing if threshold is surpassed.

Agonist

A chemical that mimics the action of a neurotransmitter.

Antagonist

A chemical that opposes or blocks the action of a neurotransmitter.

Monoamines

Group of neurotransmitters that regulates arousal, regulates feelings, and motivates behavior (e.g. norepinephrine, epinephrine, serotonin, dopamine).

Proteins

Basic chemicals that make up the structure of cells and direct their activity.

Epigenetics

The study of how the environment affects genetic expression.

Deactivation

(in some neurotransmitters) enzyme breaks down neurotransmitter and no longer binds with receptor.

EMG

Device that measures muscle movement.

EOG

Device that measures eye movement.