Psychobiology
The area of psychology that focuses on the biological foundations of behavior and mental processes.
Neuroscience
The study of the brain and nervous system.
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Neurons
Individual cells that are the smallest units 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 (tract)
Group of axons bundled together
Myelin sheath
White fatty covering found on some axons.
Sensory (afferent) neurons
Neurons that carry messages from sense organs to the spinal chord or brain.
Motor (efferent) neurons
Neurons that carry messages from the spinal chord or brain to the muscles and glands.
Interneurons (association neurons)
Neurons that carry messages from one neuron to another.
Glial cells
Cells that form the myelin sheath; they insulate and support neurons by holding them together, removing waste products, and preventing harmful substances from passing from the bloodstream to the brain.
Ions
Electrically charged particles found both inside and outside the neuron.
Resting Potential
Electrical charge across a neuron membrane due to excess positive ions concentrated on the outside and excess negative ions on the inside.
Polarization
The condition of a neuron when the inside is negatively charged related to the outside; for example, when the neuron is at rest
Neural impulse (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 states the action potential in a neuron does not vary in strength; the neuron either fires at full strength or does not fire at all.
Absolute refractory period
A period after firing when a neuron will not fire again no matter how strong the incoming messages may be.
Relative refractory period
A period after firing when a neuron is returning to its normal polarized state and will fire again only if the incoming message is much stronger than usual.
Synaptic space (synaptic cleft)
The gap between the axon terminal of one neuron and the dendrites or cell body of the next neuron.
Terminal Button (synaptic knob)
Structure at the end of the axon terminal branch.
Synapse
Area composed of the axon terminal of one neuron, the synaptic space, and the dendrite or cell body of the next neuron.
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 site
A location of 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 the environment.
Neurogenesis
The growth of new neurons.
Central nervous system
Division of the nervous system that consists of the brain and spinal chord.
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 hindbrain and 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
Network of neurons in the hindbrain, the midbrain, and part of the forebrain whose primary function is to alert and arouse higher parts of the brain.
Limbic system
Ring of structures that play a role in learning and emotional behavior.
Cerebral cortex
The outer surface of the two cerebral hemispheres that regulates the most complex behaviors.
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.
Occipital lobe
Part of the cerebral hemisphere that receives and interprets visual information.
Temporal lobe
Part of the cerebral hemisphere that helps regulate hearing, balance, and equilibrium, and certain emotions and motivations.
Parietal lobe
Part of the cerebral cortex that receives sensory information from throughout that body.
Primary somatosensory cortex
Area of the parietal lobe where messages from the sense receptors are registered.
Frontal lobe
Part of cerebral cortex responsible for voluntary movement; it is also important for attention, goal-directed behavior, and appropriate mental experiences.
Primary motor cortex
The section of the frontal lobe responsible for voluntary movement.
Corpus callosum
A thick band of nerve fibers connecting the left and right cerebral cortex.
Spinal chord
Complex cable of neurons that runs down the spine, connecting the brain to most of the rest of the body.
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 the day.
Pancreas
Organ lying between the stomach and small intestine; it regulates 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 subfield 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.
DNA
Complex molecule in a double helix configuration that is the main ingredient of chromosomes and genes and 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.
Polygenic inheritance
Process by which several genes interact to produce a certain trait; responsible for our most important traits.
Strain studies
Studies of the heritability of behavioral traits using animals that have been inbred to produce strains that are genetically similar to one another.
Selection studies
Studies that estimate the heritability of a trait by breeding animals with other animals that have the same trait.
Family studies
Studies of heritability 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 behavior.
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 behavior.