Ap Biology (Nervous Systems: 48.1)

Front 1

nerve net

Back 1

A weblike system of neurons, characteristic of radically symmetrical animals, such as hydra.

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nerve

Back 2

A ropelike bundle of neuron fibers (axons and dendrites) tightly wrapped in connective tissue.

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central nervous system (CNS)

Back 3

In vertebrate animals, the brain and spinal cord.

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ganglia

Back 4

A cluster (functional group) of nerve cell bodies in a centralized nervous system.

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peripheral nervous system (PNS)

Back 5

The sensory and motor neurons that connect to the central nervous system.

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sensory neuron

Back 6

A nerve cell that receives information from the internal and external environments and transmits the signals to the central nervous system.

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interneuron

Back 7

An association neuron; a nerve cell within the central nervous system that forms synapses with sensory and motor neurons and integrates sensory input and motor output.

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motor neuron

Back 8

A nerve cell that transmits signals from the brain or spinal cord to muscles or glands.

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effector cell

Back 9

A muscle cell or gland cell that performs the body's responses to stimuli; responds to signals from the brain or other processing center of the nervous system.

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reflex

Back 10

An automatic reaction to a stimulus, mediated by the spinal cord or lower brain.

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cell body

Back 11

The part of a neuron that houses the nucleus and other organelles.

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dendrite

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One of usually numerous, short, highly branched processes of a neuron that convey nerve impulses toward the cell body.

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axon

Back 13

A typically long extension, or process, from a neuron that carries neuron impulses away from the cell body toward target cells.

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axon hillock

Back 14

The conical region of a neuron's axon where it joins the cell body; typically the region where nerve signals are generated.

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myelin sheath

Back 15

In a neuron, an insulating coat of cell membrane from Schwann cells that is interrupted by nodes of Ranvier, where saltatory conduction occurs.

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synaptic terminal

Back 16

A bulb at the end of an axon in which neurotransmitter molecules are stored and released.

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synapse

Back 17

The locus where one neuron communicates with another neuron in a neural pathway; a narrow gap between a synaptic terminal of an axon and a signal-receiving portion (dendrite or cell body) of another neuron or effector cell. Neurotransmitter molecules released by synaptic terminals diffuse across the synapse, relaying messages to the dendrite or effector.

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presynaptic cell

Back 18

The transmitting cell at a synapse.

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postsynaptic cell

Back 19

The target cell at a synapse.

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neurotransmitters

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A chemical messenger released from the synaptic terminal of a neuron at a chemical synapse that diffuses across the synaptic cleft and binds to and stimulates the postsynaptic cell.

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glia

Back 21

Supporting cells that are essential for the structural integrity of the nervous system and for the normal functioning of neurons.

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astrocyte

Back 22

A glial cell that provides structural and metabolic support for neurons.

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blood-brain barrier

Back 23

A specialized capillary arrangement in the brain that restricts the passage of most substances into the brain, thereby preventing dramatic fluctuations in the brain's environment.

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radial glia

Back 24

In an embryo, supporting cells that form tracks along which newly formed neurons migrate from the neural tube; can also act as stem cells that give rise to neurons and other glia.

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oligodendrocytes

Back 25

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the central nervous system.

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Schwann cells

Back 26

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the peripheral nervous system.