Key terms Exam 1 Flashcards
declarative memory
Memories available to consciousness that can be expressed by language.
long-term memory
Memories that last days, weeks, months, years, or a lifetime.
nondeclarative memory
Unconscious memories such as motor skills and associations. Also called procedural memory.
action potential
The electrical signal conducted along axons (or muscle fibers) by which information is conveyed from one place to another in the nervous system.
afferent
A neuron or axon that conducts action potentials from the periphery toward the central nervous system.
anterograde
Signals or impulses that travel “forward,” e.g., from the cell body to the axon terminal, from the presynaptic terminal to the postsynaptic cell, or from the CNS to the periphery.
associational systems
Neural cell circuits that are not part of the relatively defined sensory (input) and motor (output) systems; they mediate the most complex and least well defined brain functions.
astrocytes
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.
Axon
The neuronal process that carries the action potential from the nerve cell body to a target.
axon hillock
Point at the cell body that is the site of an action potential’s initiation.
central nervous system (CNS)
The brain and spinal cord of vertebrates (by analogy, the central nerve cord and ganglia of invertebrates).
chemical synapses
Synapses that transmit information via the secretion of chemical signals (neurotransmitters).
cognitive neuroscience
The field of neuroscience devoted to studying and understanding cognitive functions.
commissures
Axon tracts that cross the midline of the brain.
computational mapping
Central process of assessing and integrating multiple stimulus attributes into an orderly representation that facilitates the extraction and processing of essential information (e.g., the number and configuration of odorant molecules in order to determine the source and nature of a smell).
convergence
Innervation of a target cell by axons from more than one neuron. In vision refers specifically to the convergence of both rod and cone photoreceptor cells onto retinal ganglion cells.
cortex
The superficial mantle of gray matter (a sheet-like array of nerve cells) covering the cerebral hemispheres and cerebellum, where most of the neurons in the brain are located.
cranial nerve ganglia
The sensory ganglia associated with the cranial nerves; these correspond to the dorsal root ganglia of the segmental nerves of the spinal cord.
dendrite
A neuronal process arising from the nerve cell body that receives synaptic input.
divergence
The branching of a single axon to innervate multiple target cells.
dorsal root ganglia (DRG)
The segmental sensory ganglia of the spinal cord; they contain the first-order neurons of the dorsal column/medial lemniscus and spinothalamic pathways.
efferent
A neuron or axon that conducts information away from the central nervous system toward the periphery.
efferent
A neuron or axon that conducts information away from the central nervous system toward the periphery.
electrical synapses
Synapses that transmit information via the direct flow of electrical current at gap junctions.
electrophysiological recording
Measure of the electrical activity across the membrane of a nerve cell by use of electrodes. Extracellular recording places the electrode outside but nearby the cell of interest; intracellular recording places the electrode is placed inside the cell of interest.
enteric system
A subsystem of the visceral motor system, made up of small ganglia and individual neurons scattered throughout the wall of the gut; influences gastric motility and secretion.
ganglion (ganglia)
Collection of hundreds to thousands of neurons found outside the brain and spinal cord along the course of peripheral nerves.
gap junction
A specialized intercellular contact formed by channels that directly connect the cytoplasm of two cells.
gene
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.
genomics
Scientific field focusing on the analysis of DNA sequences, including both protein-coding DNA (genes) and non-coding DNA.
glial cells (glia)
The support cells associated with neurons (astrocytes, oligodendrocytes, and microglial cells in the central nervous system; Schwann cells in peripheral nerves; and satellite cells in ganglia).
glial stem cells
Neural precursor cells in the adult brain that retain the capacity to proliferate and generate both additional precursor cells and differentiated glial cells (and, in some cases, differentiated neurons).
gray matter
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.
interneuron
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.
local circuit neuron
General term referring to a neuron whose activity mediates interactions between sensory systems and motor systems. Interneuron is often used as a synonym.
microglial cells
One of the three major classes of glial cells found in the central nervous system; concerned primarily with repairing damage following neural injury.
motor neuron
A broad term used to describe all the central and peripheral structures that support motor behavior.
myelin
The multilaminated wrapping around many axons formed by oligodendrocytes or Schwann cells.
myotatic reflex
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” or “deep tendon” reflex.
neurons
Cells specialized for the conduction and transmission of electrical signals in the nervous system. Also called nerve cells.
neuropil
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.
neurotransmitter
Substance released by synaptic terminals for the purpose of transmitting information from one cell (the presynaptic cell) to another (the postsynaptic cell).
nucleus (pl. nuclei)
Collection of nerve cells in the brain that are anatomically discrete, and which typically serve a particular function.
oligodendrocytes
One of the three major classes of glial cells found in the central nervous system; their major function is to lay down myelin.
parasympathetic nervous system
A division of the visceral motor system in which the effectors are cholinergic ganglion cells located near target organs.
peripheral nervous system (PNS)
All nerves and neurons that lie outside the brain and spinal cord.
postsynaptic
Referring to the component of a synapse specialized for transmitter reception; downstream at a synapse.
presynaptic
Referring to the component of a synapse specialized for transmitter release; upstream at a synapse.
projection neuron
A neuron with long axons that project to distant targets.
receptive field
The region of a receptive surface (e.g., the body surface, or a specialized structure such as the retina) within which a specific stimulus elicits the greatest action potential response from sensory cells.
receptor potential
The membrane potential change elicited in receptor neurons during sensory transduction. Also called generator potential.
retrograde
Signals or impulses that travel “backward,” e.g., from the axon terminal toward the cell body, or from the postsynaptic cell to the presynaptic terminal, or from the periphery to the CNS.
Schwann cells
Glial cells in the peripheral nervous system that lay down myelin (named after the nineteenth-century anatomist and physiologist Theodor Schwann).
sensory system
Term sometimes used to describe all the components of the central and peripheral nervous system concerned with sensation.
spinal cord
The portion of the central nervous system that extends from the lower end of the brainstem (the medulla) to the cauda equina.
sympathetic nervous system
A division of the visceral motor system in vertebrates comprising, for the most part, adrenergic ganglion cells located relatively far from the related end organs.
synaptic cleft
The space that separates pre- and postsynaptic neurons at chemical synapses.
synaptic transmission
The chemical and electrical process by which the information encoded by action potentials is passed from a presynaptic (initiating) cell to a postsynaptic (target) cell.
synaptic vesicles
Spherical, membrane-bound organelles in presynaptic terminals that store neurotransmitter molecules.
visceral
Referring to the internal organs of the body cavity, particularly the gut.
white matter
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.
action potential
The electrical signal conducted along axons (or muscle fibers) by which information is conveyed from one place to another in the nervous system.
active transporters
Transmembrane proteins that actively move ions into or out of cells against their concentration gradients. Their source of energy may be ATP or the electrochemical gradients of various ions.
depolarization
Displacement of a cell’s membrane potential toward a less negative value.
electrochemical equilibrium
The condition in which no net ionic flux occurs across a membrane because ion concentration gradients and opposing transmembrane potentials are in exact balance.
equilibrium potential
The membrane potential at which a given ion is in electrochemical equilibrium.
hyperpolarization
The displacement of a cell’s membrane potential toward a more negative value.
ion channels
Integral membrane proteins possessing pores that allow only certain ions to diffuse across cell membranes, thereby conferring selective ionic permeability.
Nernst equation
A mathematical formula that predicts the electrical potential generated ionically across a membrane at electrochemical equilibrium.
overshoot phase
The peak, positive-going phase of an action potential, caused by high membrane permeability to a cation such as Na+ or Ca2+.
passive flow
The flow of electrical current across neuronal membranes that does not entail the action potential mechanism.
receptor potential
The membrane potential change elicited in receptor neurons during sensory transduction. Also called generator potential.
rising phase
The initial, depolarizing, phase of an action potential, caused by the regenerative, voltage-dependent influx of a cation such as Na+ or Ca2+.
threshold potential
The level of membrane potential at which an action potential is generated.
undershoot
The final, hyperpolarizing phase of an action potential, typically caused by the voltage-dependent efflux of a cation such as K+.
conduction velocity
The speed at which an action potential is propagated along an axon.
membrane conductance
The reciprocal of membrane resistance. Changes in membrane conductance result from, and are used to describe, the opening or closing of ion channels.
membrane conductance
The reciprocal of membrane resistance. Changes in membrane conductance result from, and are used to describe, the opening or closing of ion channels.
myelin
The multilaminated wrapping around many axons formed by oligodendrocytes or Schwann cells.
myelination
Process by which glial cells (oligodendrocytes or Schwann cells) wrap around axons to form multiple layers of glial cell membrane, thus insulating the axonal membrane and increasing conduction velocity.
nodes of Ranvier
Periodic gaps in the myelination of axons where action potentials are generated.
refractory period
The brief period after the generation of an action potential during which a second action potential is difficult or impossible to elicit.
saltatory conduction
Mechanism of action potential propagation in myelinated axons; so named because action potentials “jump” from one node of Ranvier to the next due to generation of action potentials only at these sites.
