The Nervous System and Nervous Tissue (OpenStax Ch12)

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Absolute refractory period

Back

Time during an action potential when another action potential cannot be generated because the voltage-gated Na⁺ channel is inactivated.

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Action Potential

Back

A change in the voltage of a cell membrane in response to a stimulus that results in the transmission of an electrical signal; unique to neurons and muscle fibers.

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Activation Gate

Back

Part of the voltage-gated Na⁺ channel that opens when the membrane voltage reaches the threshold.

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Astrocyte

Back

A type of glial cell in the CNS that provides support for neurons and maintains the blood-brain barrier.

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Autonomic Nervous System (ANS)

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A functional division of the nervous system responsible for homeostatic reflexes that coordinate control of cardiac and smooth muscle, as well as glandular tissue.

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Axon

Back

A single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell.

Front

Axon hillock

Back

The tapering of the neuron cell body that gives rise to the axon.

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Axon segment

Back

A single stretch of the axon insulated by myelin and bounded by nodes of Ranvier at either end, except for the first, which is after the initial segment, and the last, which is followed by the axon terminal.

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Axon terminal

Back

The end of the axon, where there are usually several branches extending toward the target cell.

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Axoplasm

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The cytoplasm of an axon, which differs in composition from the cytoplasm of the neuronal cell body.