Neuroscience Chapter 1 Key Terms

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action potential

Back 1

The electrical signal conducted along axons (or muscle fibers) by which information is conveyed from one place to another in the nervous system.

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astrocytes

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One of the three major classes of glial cells found in the central nervous system; important in regulating the ionic milieu of nerve cells and, in some cases, transmitter reuptake.

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axon

Back 3

The neuronal process that carries the action potential from the nerve cell body to a target.

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brain-derived neutrophic factor (BDNF)

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One member of a family of neutrophic factors, the best-known constituent of which is nerve growth factor.

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central nervous system (CNS)

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The brain and spinal cord of vertebrates (by analogy, the central nerve cord and ganglia of invertebrates).

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chemical synapses

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Synapses that transmit information via the secretion of chemical signals (neurotransmitters).

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convergence

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Innervation of a target cell by axons from more than one neuron.

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cortex

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The superficial mantle of gray matter covering the cerebral hemispheres and cerebellum, where most of the neurons in the brain are located.

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cranial nerve ganglia

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The sensory ganglia associated with the cranial nerves; these correspond to the dorsal root ganglia of the spinal segmental nerves.

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dendrite

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A neuronal process arising from the cell body that receives synaptic input.

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divergence

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The branching of a single axon to innervate multiple target cells.

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dorsal root ganglia (DRG)

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The segmental sensory ganglia of the spinal cord; contain the first-order neurons of the dorsal column/medial lemniscus and spinothalamic pathways.

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efferent

Back 13

An axon that conducts information away from the central nervous system.

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electrical synapses

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Synapses that transmit information via the direct flow of electrical current at gap junctions.

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ganglion (ganglia)

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Collections of hundreds to thousands of neurons found outside the brain and spinal cord along the course of peripheral nerves.

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gene

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Hereditary unit located on the chromosomes; genetic information is carried by linear sequences of nucleotides
in DNA that code for corresponding sequences of amino acids.

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glia

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The support cells associated with neurons (astrocytes, oligodendrocytes, and microglia in the central nervous system; Schwann cells in peripheral nerves; and satellite cells in ganglia). Also known as neuroglia.

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gray matter

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General term that describes regions of the central nervous system rich in neuronal cell bodies and neuropil; includes the cerebral and cerebellar cortices, the nuclei of the brain, and the central portion of the spinal cord.

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interneuron

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Technically, a neuron in the pathway between primary sensory and primary effector neurons; more generally, a neuron whose relatively short axons branch locally to innervate other neurons. Also known as local circuit neuron.

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local circuit neuron

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General term referring to neurons whose activity mediates interactions between sensory systems and motor
systems; interneuron is often used as a synonym.

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microglial cells

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One of the three main types of central nervous system glia; concerned primarily with repairing damage following neural injury.

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motor
neuron

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By usage, a nerve cell that innervates skeletal muscle. Also called primary or α motor neuron.

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motor
system

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A broad
term used to describe all the central and peripheral structures that support motor behavior.

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myelin

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The multilaminated
wrapping around many axons formed by oligodendrocytes or Schwann cells.

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myotatic reflex

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A fundamental spinal reflex that is generated by the motor response to afferent sensory information arising from muscle spindles. The “knee jerk reaction” is a common example. Also called a stretch reflex.

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nerve

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A collection of peripheral axons that are bundled together and travel a common route.

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neuron

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Cell specialized for the conduction and transmission of electrical signals in the nervous system.

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neuropil

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The dense tangle of axonal and dendritic branches, and the synapses between them, that lies between neuronal cell bodies in the gray matter of the brain and spinal cord.

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neurotransmitter

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Substance released by synaptic terminals for the purpose of transmitting information from one nerve cell to another.

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nucleus (nuclei)

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Collection of nerve cells in the brain that are anatomically discrete, and which typically serve a particular function.

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oligodendrocytes

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One of three classes of central neuroglial cells; their major function is to elaborate myelin.

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peripheral nervous system

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All nerves and neurons that lie outside the brain and spinal cord.

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projection neuron

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A neuron with long axons that project to distant targets.

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receptive field

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Region of a receptor surface (e.g., the body surface or the retina) that causes a sensory nerve cell (or axon) to respond.

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receptor potential

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The membrane potential change elicited in receptor neurons during sensory transduction.

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Schwann cells

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Neuroglial cells in the peripheral nervous system that elaborate myelin (named after the nineteenth-century anatomist and physiologist Theodor Schwann).

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sensory system

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Term sometimes used to describe all the components of the central and peripheral nervous system concerned with sensation.

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spinal cord

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The portion of the central nervous system that extends from the lower end of the brainstem (the medulla) to the cauda equina.

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synaptic cleft

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The space that separates pre- and postsynaptic neurons at chemical synapses.

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synaptic vesicle recycling

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A sequence of budding and fusion reactions that occurs within presynaptic terminals to maintain the supply of synaptic vesicles.

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white matter

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A general term that refers to large axon tracts in the brain and spinal cord; the phrase derives from the fact that axonal tracts have a whitish cast when viewed in the freshly cut material.