Terms

Psychobiology

The area of psychology that focuses on the biological foundations of behavior and mental processes.

Neurons

Individual cells that are the smallest unit of the nervous system.

Dendrites

Short fibers that branch out from the cell body and pick up incoming messages.

Axon

Single long fiber extending from the cell body, it carries outgoing messages.

Nerve (or tract)

Group of axons bundled together.

Myelin sheath

White fatty covering found on some axons.

Sensory (or afferent) neurons

Neurons that carry messages from sense organs to the spinal cord or brain.

Motor (or efferent) neurons

Neurons that carry messages from the spinal cord or brain to the muscles and glands.

Interneurons (or association neurons)

Neurons that carry messages from one neuron to another.

Glial cells (or glia)

Cells that insulate and support neurons by holding them together, provide nourishment and remove waste products, prevent harmful substances from passing into the brain, and form the myelin sheath.

Ions

Electrically charged particles found both inside and outside the neuron.

Resting potential

Electrical charge across a neuron membrane resulting from more positive ions concentrated on the outside and more negative ions on the inside.

Polarization

The condition of a neuron when the inside is negatively charged relative to the outside; for example, when the neuron is at rest.

Neural impulse (or action potential)

The firing of a nerve cell.

Graded potential

A shift in the electrical charge in a tiny area of a neuron.

Threshold of excitation

The level an impulse must exceed to cause a neuron to fire.

All-or-none law

Principle that the action potential in a neuron does not vary in strength; either the neuron fires at full strength, or it does not fire at all.

Synaptic space (or synaptic cleft)

Tiny gap between the axon terminal of one neuron and the dendrites or cell body of the next neuron.

Synapse

Area composed of the axon terminal of one neuron, the synaptic space, and the dendrite or cell body of the next neuron.

Terminal button (or synaptic knob)

Structure at the end of an axon terminal branch.

Synaptic vesicles

Tiny sacs in a terminal button that release chemicals into the synapse.

Neurotransmitters

Chemicals released by the synaptic vesicles that travel across the synaptic space and affect adjacent neurons.

Receptor sites

Locations on a receptor neuron into which a specific neurotransmitter fits like a key into a lock.

Neural Plasticity

            The ability of the brain to change in response to activity.

Neurogenesis

            The growth of new neurons

Central nervous system

Division of the nervous system that consists of the brain and spinal cord.

Peripheral nervous system

Division of the nervous system that connects the central nervous system to the rest of the body.

Hindbrain

Area containing the medulla, pons, and cerebellum.

Cerebellum

Structure in the hindbrain that controls certain reflexes and coordinates the body's movements.

Midbrain

Region between the hindbrain and the forebrain; it is important for hearing and sight, and it is one of several places in the brain where pain is registered.

Thalamus

Forebrain region that relays and translates incoming messages from the sense receptors, except those for smell.

Hypothalamus

Forebrain region that governs motivation and emotional responses.

Reticular formation (RF)

Network of neurons in the hindbrain, the midbrain, and part of the forebrain whose primary function is to alert and arouse the higher parts of the brain.

Cerebral cortex

The outer surface of the two cerebral hemispheres that regulates the most complex behavior.

Frontal lobe

Part of the cerebral cortex that is responsible for voluntary movement; it is also important for attention, goal-directed behavior, and appropriate emotional experiences.

Association areas

Areas of the cerebral cortex where incoming messages from the separate senses are combined into meaningful impressions and outgoing messages from the motor areas are integrated.

Primary motor cortex

The section of the frontal lobe responsible for voluntary movement.

Occipital lobe

Part of the cerebral hemisphere that receives and interprets visual information.

Parietal lobe

Part of the cerebral cortex that receives sensory information from throughout the body.

Temporal lobe

Part of the cerebral hemisphere that helps regulate hearing, balance and equilibrium, and certain emotions and motivations.

Limbic system

            Ring of structures that plays a role in learning and emotional behavior.

Corpus callosum

            A thick band of nerve fibers connecting the left and the right cerebral cortex.

Spinal cord

            Complex cable of neurons that runs down the spine, connecting the brain to most of the rest of the body.

Afferent neurons

Neurons that carry messages from sense organs to the spinal cord or brain.

Efferent neurons

Neurons that carry messages from the spinal cord or brain to the muscles and glands.

Somatic nervous system

The part of the peripheral nervous system that carries messages from the senses to the central nervous system and between the central nervous system and the skeletal muscles.

Autonomic nervous system

The part of the peripheral nervous system that carries messages between the central nervous system and the internal organs.

Sympathetic division

Branch of the autonomic nervous system; it prepares the body for quick action in an emergency.

Parasympathetic division

Branch of the autonomic nervous system; it calms and relaxes the body.

Endocrine glands

Glands of the endocrine system that release hormones into the bloodstream.

Hormones

Chemical substances released by the endocrine glands, they help regulate bodily activities.

Thyroid gland

            Endocrine gland located below the voice box; it produces the hormone thyroxin.

Parathyroids

Four tiny glands embedded in the thyroid; they secrete parathormone.

Pineal gland

A gland located roughly in the center of the brain that appears to regulate activity levels over the course of a day.

Pancreas

Organ lying between the stomach and small intestine; it secretes insulin and glucagon to regulate blood-sugar levels.

Pituitary gland

Gland located on the underside of the brain; it produces the largest number of the body's hormones.

Gonads

The reproductive glands-testes in males and ovaries in females.

Adrenal glands

Two endocrine glands located just above the kidneys.

Behavior genetics

Study of the relationship between heredity and behavior.

Evolutionary psychology

A sub-field of psychology concerned with the origins of behaviors and mental processes, their adaptive value, and the purposes they continue to serve.

Genetics

Study of how traits are transmitted from one generation to the next.

Genes

Elements that control the transmission of traits; they are found on the chromosomes.

Chromosomes

Pairs of threadlike bodies within the cell nucleus that contain the genes.

Deoxyribonucleic acid (DNA)

Complex molecule in a double-helix configuration that is the main ingredient of chromosomes and genes and that forms the code for all genetic information.

Human genome

The full complement of genes within a human cell.

Dominant gene

Member of a gene pair that controls the appearance of a certain trait.

Recessive gene

Member of a gene pair that can control the appearance of a certain trait only if it is paired with another recessive gene. The twisted chain of the long DNA molecule contains the genetic code.

Polygenic inheritance

Process by which several genes interact to produce a certain trait, responsible for our most important traits.

Behavior genetics

Study of the relationship between genetics and behavior.

Family studies

Studies of habitability in humans based on the assumption that if genes influence a certain trait, close relatives should be more similar on that trait than distant relatives.

Twin studies

Studies of identical and fraternal twins to determine the relative influence of heredity and environment on human behavior.

Identical twins

Twins developed from a single fertilized ovum and therefore identical in genetic makeup at the time of conception.

Fraternal twins

Twins developed from two separate fertilized ova and therefore different in genetic makeup.

Adoption studies

Research carried out on children, adopted at birth by parents not related to them, to determine the relative influence of heredity and environment on human behavior.

Human genome

            The full compliment of genes within a human cell.

Natural selection

The mechanism proposed by Darwin in his theory of evolution, which states that organisms best adapted to their environment tend to survive, transmitting their genetic characteristics to succeeding generations, whereas organisms with less adaptive characteristics tend to vanish from the earth.