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The minimum length of time after an action potential during which another action potential cannot begin.

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Action potential

A brief change in a neuron’s electrical charge

Adaptation

An inherited characteristic that increased in a population (through natural selection) because it helped solve a problem of survival or reproduction during the time it emerged.

Afferent nerve fibers

Antagonist

A chemical that opposes the action of a neurotransmitter.

Autonomic nervous system (ANS)

The system of nerves that connect to the heart, blood vessels, smooth muscles, and glands.

Axon

A long, thin fiber that transmits signals away from the neuron cell body to other neurons, or to muscles or glands.

Central nervous system (CNS)

Consists of Brain and spinal cord

Cerebellum

 A relatively large and deeply folded structure located adjacent to the back surface of the brainstem.[image]

Cerebral cortex

 The convoluted outer layer of the cerebrum.[image][image][image][image][image]

Cerebral hemispheres

The right and left halves of the cerebrum.

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Chromosomes

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 Threadlike strands of DNA (deoxyribonucleic acid) molecules that carry genetic information.

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Corpus callosum

Critical period

A limited time span in the development of an organism when it is optimal for certain capacities to emerge because the organism is especially responsive to certain experiences.

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

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Efferent nerve fibers

Sending a weak electric current into a brain structure to stimulate (activate) it.

Endocrine system

A group of glands that secrete chemicals into the bloodstream that help control bodily functioning.

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Endorphins

The entire family of internally produced chemicals that resemble opiates in structure and effects.

Family studies

The reproductive success (number of descendants) of an individual organism relative to the average reproductive success of the population.

Forebrain

 The largest and most complicated region of the brain, encompassing a variety of structures, including the thalamus, hypothalamus, limbic system, and cerebrum.

Genes

DNA segments that serve as the key functional units in hereditary transmission.

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Glia

Cells found throughout the nervous system that provide various types of support for neurons.

Hindbrain

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The part of the brain that includes the cerebellum and two structures found in the lower part of the brainstem: the medulla and the pons.

Hormones

The chemical substances released by the endocrine glands.

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A structure found near the base of the forebrain that is involved in the regulation of basic biological needs.

Lesioning

Limbic system

A densely connected network of structures roughly located along the border between the cerebral cortex and deeper subcortical areas.

Midbrain

The segment of the brain stem that lies between the hindbrain and the forebrain.

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Myelin sheath

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Insulating material, derived from glial cells, that encases some axons of neurons.

Principle stating that inherited characteristics that provide a survival or reproductive advantage are more likely than alternative characteristics to be passed on to subsequent generations and thus come to be “selected” over time.

Neurons

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Neurotransmitters

Peripheral nervous system

Pituitary gland

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The “master gland” of the endocrine system; it releases a great variety of hormones that fan out through the body, stimulating actions in the other endocrine glands.

Postsynaptic potential (PSP)

Resting potential

The stable, negative charge of a neuron when it is inactiv

Reuptake

A process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane.

Soma

The cell body of a neuron; it contains the nucleus and much of the chemical machinery common to most cells.

Somatic nervous system

Synapse

A microscopic gap between the terminal button of a neuron and the cell membrane of another neuron.

Terminal buttons

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Small knobs at the end of axons that secrete chemicals called neurotransmitters.

Thalamus

A structure in the forebrain through which all sensory information (except smell) must pass to get to the cerebral cortex.[image]

Twin studies

A research design in which hereditary influence is assessed by comparing the resemblance of identical twins and fraternal twins with respect to a trait.