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Neuroscience Chapter 2: Nervous System Cells
Structure and Functions of Cells of the Nervous System.
88
Science
11th Grade
08/18/2011

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Term
Sensory neuron
Definition
A neuron that detects changes in the external or internal environment and sends information about these changes to the central nervous system.
Term
Motor neuron
Definition
A neuron located within the central nervous system that controls the contraction of a muscle or the secretion of a gland.
Term
Interneuron
Definition
A neuron located entirely within the central nervous system.
Term
Central nervous system (CNS)
Definition
The brain and spinal cord.
Term
Peripheral nervous system (PNS)
Definition
The part of the nervous system outside the brain and spinal cord, including the nerves attached to the brain and spinal cord.
Term
Soma
Definition
The cell body of a neuron, which contains the nucleus.
Term
Dendrite
Definition
A branched, treelike structure attached to the soma of a neuron; receives information from the terminal buttons of other neurons.
Term
Synapse
Definition
A junction between the terminal button of an axon and the membrane of another neuron.
Term
Axon
Definition
The long, thin, cylindrical structure that conveys information from the soma of a neuron to its terminal buttons.
Term
Multipolar neuron
Definition
A neuron with one axon and many dendrites attached to its soma.
Term
Bipolar neuron
Definition
A neuron with one axon and one dendrite attached to its soma.
Term
Unipolar neuron
Definition
A neuron with one axon attached to its soma; the axon divides, one branch receiving sensory information and the other sending the information into the central nervous system.
Term
Terminal button
Definition
The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron.
Term
Neurotransmitter
Definition
A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron.
Term
Membrane
Definition
A structure consisting principally of lipid molecules that defines the outer boundaries of a cell and also constitutes many of the cell organelles.
Term
Cyctoplasm
Definition
The viscous, semiliquid substance contained in the interior of a cell.
Term
Mitochondria
Definition
An organelle that is responsible for extracting energy from nutrients.
Term
Adenosine triphosphate (ATP)
Definition
A molecule of prime importance to cellular energy metabolism; its breakdown liberates energy.
Term
Nucleus
Definition
A structure in the central region of a cell, containing the chromosomes.
Term
Chromosome
Definition
A strand of DNA, with associated proteins, found in the nucleus; carries genetic information.
Term
Deoxyribonucleic acid (DNA)
Definition
A long, complex macromolecule consisting of two interconnected helical strands; along with associated proteins, strands of DNA constitute the chromosomes.
Term
Gene
Definition
The functional unit of the chromosome, which directs synthesis of one or more proteins.
Term
Cytoskeleton
Definition
Formed of microtubules and other protein fibers, linked to each other and forming a cohesive mass that gives a cell its shape.
Term
Enzyme
Definition
A molecule that controls a chemical reaction, combining two substances or breaking a substance into two parts.
Term
Axoplasmic transport
Definition
An active process by which substances are propelled along the microtubules that run the length of the axon.
Term
Microtubule
Definition
A long strand of bundles of protein filaments arranged around a hollow core; part of the cytoskeleton and involved in transporting substances from place to place within the cell.
Term
Glia
Definition
The supporting cells of the central nervous system.
Term
Astrocyte
Definition
A glial cell that provides support for neurons of the central nervous system, provides nutrients and other substances, and regulates the chemical composition of the extracellular fluid.
Term
Phagocytosis
Definition
The process by which cells engulf and digest other cells or debris caused by cellular regeneration.
Term
Ogliodendrocyte
Definition
A type of glial cell in the central nervous system that forms myelin sheaths.
Term
Myelin sheath
Definition
A sheath that surrounds axons and insulates them, preventing messages from spreading between adjacent axons.
Term
Node of Ranvier
Definition
A naked portion of a myelinated axon, between adjacent ogliodendroglia or Schwann cells.
Term
Microglia
Definition
The smallest of glial cells, act as phagocytes and protect the brain from invading microorganisms.
Term
Schwann cell
Definition
A cell in the peripheral nervous system that is wrapped around a myelinated axon, providing one segment of its myelin sheath.
Term
Blood-brain barrier
Definition
A semipermeable barrier between the blood and the brain produced by the cells in the walls of the brain's capillaries.
Term
Area postrema
Definition
A region of the medulla where the blood-brain barrier is weak; poisons can be detected there and can initiate vomiting.
Term
Electrode
Definition
A conductive medium that can be used to apply electrical stimulation or to record electrical potentials.
Term
Microelectrode
Definition
A very fine electrode, generally used to record the activity of individual neurons.
Term
Membrane potential
Definition
The electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell.
Term
Oscilloscope
Definition
A laboratory instrument that is capable of displaying a graph of voltage as a function of time on the face of a cathode ray tube.
Term
Resting potential
Definition
The membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials; approximately -70 mV in the giant squid axon.
Term
Depolarization
Definition
Reduction (toward zero) of the membrane potential of a cell from its normal resting potential.
Term
Hyperpolarization
Definition
An increase in the membrane potential of a cell, relative to the normal resting potential.
Term
Action potential
Definition
The brief electrical impulse that provides the basis for conduction of information along an axon.
Term
Threshold of excitation
Definition
The value of the membrane potential that must be reached to produce an action potential.
Term
Diffusion
Definition
Movement of molecules from regions of high concentration to regions of low concentration.
Term
Electrolyte
Definition
An aqueous solution of a material that ionizes- namely, a soluble acid, base, or salt.
Term
Ion
Definition
A charged molecule. Cations are positively charged, and anions are negatively charged.
Term
Electrostatic pressure
Definition
The attractive force between atomic particles charged with opposite sides or the repulsive force between atomic particles charged with the same side.
Term
Intracellular fluid
Definition
The fluid contained within cells.
Term
Intracellular fluid
Definition
The fluid contained within cells.
Term
Extracellular fluid
Definition
Body fluids located outside of cells.
Term
Sodium-potassium transporter
Definition
A protein found in the membrane of all cells that extrudes sodium ions from and transports potassium ions into the cell.
Term
Ion channel
Definition
A specialized protein molecule that permits specific ions to enter or leave cells.
Term
Voltage-dependent ion channel
Definition
An ion channel that opens or closes according to the value of the membrane potential.
Term
All-or-none law
Definition
The principle that once an action potential is triggered in an axon, it is propagated, without decrement, to the end of the fiber.
Term
Rate law
Definition
The principle that variations in the intensity of a stimulus or other information being transmitted in an axon are represented by variations in the rate at which the axon fires.
Term
Saltatory conduction
Definition
Conduction of action potentials by myelinated ions. The action potential appears to jump from one node of Ranvier to the next.
Term
Postsynaptic potential
Definition
Alterations in the membrane potential of a post-synaptic neuron, produced by liberation of neurotransmitter at the synapse.
Term
Binding site
Definition
The location on a receptor protein to which a ligand binds.
Term
Ligand
Definition
A chemical that binds with the binding site of a receptor.
Term
Dendritic spine
Definition
A small bud on the surface of a dendrite, with which a terminal button of another neuron forms a synapse.
Term
Presynaptic membrane
Definition
The membrane of a terminal button that lies adjacent to the postsynaptic membrane and through which the neurotransmitter is released.
Term
Postsynaptic membrane
Definition
The cell membrane opposite the terminal button in a synapse; the membrane of the cell that receives the message.
Term
Synaptic cleft
Definition
The space between the presynaptic membrane and the postsynaptic membrane.
Term
Synaptic vesicle
Definition
A small, hollow, beadlike structure found in terminal buttons; contains molecules of a neurotransmitter.
Term
Release zone
Definition
A region of the interior of the presynaptic membrane of a synapse to which synaptic vesicles attach and release their neurotransmitter into the synaptic cleft.
Term
Postsynaptic receptor
Definition
A receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter.
Term
Neurotransmitter-dependent ion channel
Definition
An ion channel that opens when a molecule of a neurotransmitter binds with a postsynaptic receptor.
Term
Ionotropic receptor
Definition
A receptor that contains a binding site for a neurotransmitter and ion channel that opens when a molecule of the neurotransmitter attaches to the binding site.
Term
Metabotropic receptor
Definition
A receptor that contains a binding site for a neurotransmitter; activates an enzyme that begins a series of events that opens an ion channel elsewhere in the membrane of the cell when a molecule of the neurotransmitter attaches to the binding site.
Term
G protein
Definition
A protein coupled to a metabotropic receptor; conveys messages to other molecules when a ligand binds with and activates the receptor.
Term
Second messenger
Definition
A chemical produced hewn a G protein activates an enzyme; carries a signal that results in the opening of the ion channel or causes other events to occur in the cell.
Term
Excitatory postsynaptic potential (EPSP)
Definition
An excitatory depolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button.
Term
Inhibitory postsynaptic potential (IPSP)
Definition
An inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button.
Term
Reuptake
Definition
The reentry of a neurotransmitter just liberated by a terminal button back through its membrane, thus terminating the postsynaptic potential.
Term
Enzymatic deactivation
Definition
The destruction of a neurotransmitter by an enzyme after its release- for example, the destruction of acetylcholine by acetylcholinesterase.
Term
Acetylcholine (ACh)
Definition
A neurotransmitter found in the brain, spinal cord, and parts of the peripheral nervous system; responsible for muscular contraction.
Term
Acetylcholinesterase
Definition
The enzyme that destroys acetylcholine soon after it is liberated by the terminal button, thus terminating the post-synaptic potential.
Term
Neural integration
Definition
The process by which inhibitory and excitatory postsynaptic potentials summate and control the rate of firing of a neuron.
Term
Autoreceptor
Definition
A receptor molecule located on a neuron that responds to the neurotransmitter released by that neuron.
Term
Presynaptic inhibition
Definition
The action of a presynaptic terminal button in an axoaxonic synapse; reduces the amount of neurotransmitter released by the postsynaptic terminal button.
Term
Presynaptic facilitation
Definition
The action of a presynaptic terminal button in an axoaxonic synapse; increases the amount of neurotransmitter released by the postsynaptic terminal button.
Term
Neuromodulator
Definition
A naturally secreted substance that acts like a neurotransmitter except that it is not restricted to the synaptic cleft but diffuses through the extracellular fluid.
Term
Peptide
Definition
A chain of amino acids joined together by peptide bonds. Most neuromodulators and some hormones consist of peptide molecules.
Term
Hormone
Definition
A chemical substance that is released by an endocrine gland and that has effects on target cells in other organs.
Term
Endocrine gland
Definition
A gland that liberates its secretions into the extracellular fluid around capillaries and hence into the bloodstream.
Term
Target cell
Definition
The type of cell that contains receptors for a particular hormone and is affected by that hormone.
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