Start Key Terms: Anatomy & Physiology Key Terms Nervous System

Question: activation gate

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

Question: axon terminal

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

Question: axon hillock

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

Question: biogenic amine

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class of neurotransmitters that are enzymatically derived from amino acids but no longer contain a carboxyl group

Question: autonomic nervous system (ANS)

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

Question: axoplasm

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cytoplasm of an axon, which is different in composition than the cytoplasm of the neuronal cell body

Question: axon

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

Question: action potential

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

Question: axon segment

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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)

Question: astrocyte

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

Question: absolute refractory period

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