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Chapter 2
Cells of the Nervous System
105
Psychology
Graduate
10/03/2016

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Term
Central Nervous System (CNS)
Definition
The brain and the 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
Sensory Neurons
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 Neurons
Definition
A neuron located within the central nervous system that controls the contraction of a muscle of the secretion of gland.
Term
Interneurons
Definition
A neuron located entirely within the central nervous system. In between sensory and motor neurons.
Term
Soma
Definition
The cell body of a neuron, which contains the nucleus.
Term
Dendrites
Definition
A branched, treelike structure attached to the soma of a neuron; receives information from 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
Terminal Buttons
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
Axoplasmic Transport
Definition
An active process by which substances are propelled along microtubules that run the length of the axon.
Term
Anterograde
Definition
In a direction along an axon from the cell body toward the terminal buttons. (Kinesin)
Term
Retrograde
Definition
In a direction along an axon from the terminal buttons toward the cell body. (Dynein) - 1/2 the speed of anterograde
Term
Membrane
Definition
A structure consisting principally of lipid molecules that defines the outer boundaries of a cell and also constitutes many of the organelles, such as the Golgi Aperatus.
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
Microtubules
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
Cytoplasm
Definition
The viscous, semi liquid substance contained in the interior of a cell.
Term
Nucleus
Definition
A structure in the central region of a cell, containing the nucleolus and chromosomes.
Term
Nucleolus
Definition
A structure within the nucleus that produces ribosomes.
Term
Ribosomes
Definition
A cytoplasmic structure, made of protein that serves as the site of production of proteins translated from mRNA.
Term
Chromosome
Definition
A strand of DNA, with associated proteins, found in the nucleus; carries genetic information.
Term
Deoxyribronucleic acid (DNA)
Definition
A long, complex macromolecule consisting of two interconnected helical strands; along with associated proteins, strands of DNA constitute the chromosome. - contains the organism's genetic information
Term
Messenger ribonucleic acid (mRNA)
Definition
A macromolecule that delivers genetic information concerning the synthesis of a protein from a portion of a chromosome to a ribosome.
Term
Enzymes
Definition
A molecule that controls a chemical reaction, combing two substances or breaking a substance into two parts.
Term
Endoplasmic Reticulum
Definition
Parallel layers of membrane found withing the cytoplasm of a cell.
Term
Rough Endoplasmic Reticulum
Definition
Contains ribosomes and is involved with production of proteins that are secreted by the cell
Term
Smooth endoplasmic Reticulum
Definition
The site of synthesis of lipids and prov ides channels for the segregation of molecules involved in various cellular processes.
Term
Golgi Apparatus
Definition
A complex of parallel membranes in the cytoplasm that wraps the products of a secretory cell.
Term
Exocytosis
Definition
The secretion of a substance by a cell through means of vesicles; the process by which neurotransmitters are secreted.
Term
Lysosomes
Definition
An organelle surrounded by membrane; contains enzymes that break down waste product - clean up cells.
Term
Mitochondria
Definition
An organelle that is responsible for extracting energy from nutrients.
*Provides cell with ATP
Term
Adenosine Triphosphate (ATP)
Definition
A molecule of prime importance to cellular energy metabolism; its breakdown liberates energy.
Term
glia
Definition
The supporting cells of the central nervous system.
*Surround neurons and hold them in place, insulate neurons from each other, and act as a housekeeper.
Term
Astrocycte
Definition
"Star Cell" - 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 extra cellular fluid.
Term
Phagocytosis
Definition
The process by which cells engulf and digest other cells or debris caused by cellular degeneration.
Term
Oligodendrocyctes
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 oligodendrolia or Schwann cells.
Term
Microglia
Definition
The smallest of the glial cells; they act as phagocytes and protect the brain from invading microorganisms.
Term
Schwann
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 vomitting.
Term
Membrane Potential
Definition
The electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell.
Term
Resting Potential
Definition
The membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials; approximately -70mV in the giant squid axon.
Term
Hyperpolarized
Definition
An increase in the membrane potential of a cell, relative to the normal resting potential; membrane potential becomes more negative.
Term
Depolarization
Definition
Reduction(towards zero) of the membrane potential of a cell from its normal resting potential; membrane potential becomes more positive.
Term
Threshold of Excitation
Definition
The value of the membrane potential that must be reached to produce an action potential.
Term
Action Potential
Definition
The brief electrical impulse that provides the basis for conduction of information along an axon.
Term
Diffusion
Definition
Movement of molecules from regions of high concentration to regions of low concentration.
Term
Electrocytes
Definition
An aqueous solution of a material that ionizes - namely, a soluble acid, base, or salt.
Term
Ions
Definition
A charged molecule.
Term
Cations
Definition
Positively charged ions.
Term
Anions
Definition
Negatively charged ions
Term
Electrostatic Pressure
Definition
The attractive force between atomic particles charged with opposite signs or the repulsive force between atomic particles charged with the same sign.
Term
Intracellular Fluid
Definition
The fluid contained within cells.
Term
Extracellular Fluid
Definition
Body fluids located outside of the cells.
Term
Sodium-Potassium Pump
Definition
A protein found in the membrane of all cells that extrudes sodium ions from and transports potassium ions into the cell.
Term
Ion Channels
Definition
A specialized protein molecule that permits specific ions to enter or leave cells.
Term
Voltage-Dependent Ion Channels
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 int he intensity of a stimulus or other information being transmitted in an axon are represented by variations in the rate at which that axon fires.
Term
Saltatory Conduction
Definition
Conduction of action potentials by myelinated axons. The action potential appears to jump from one node of Ranvier to the next.
Term
Postsynaptic Potential
Definition
Alteration int he membrane potential of a postsynaptic neuron, produced by liberation of neurotransmitter at the synapse.
Term
Binding Site
Definition
The location on a receptor protein to which a ligard binds.
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 Vesicles
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
Ready release vesicles
Definition
<1% of vesicles - "kiss and run" - docked against the inside of the presynaptic membrane. Low rate of axon firing.
Term
Recycling pool Vesicles
Definition
10-15% - fuse with membrane when axon firing rate increases.
Term
Reserve Pool Vesicles
Definition
(85-90%) Recycles through bulk endocytosis and used when axon firing rate increases
Term
Postsynaptic receptors
Definition
A receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter
Term
Endocytosis
Definition
The process of entering a cell.
Term
Neurotransmitter-dependent ion channels
Definition
An ion channel that opens when a molecule of a neurotransmitter binds with a post synaptic receptor.
Term
Ionotophic Receptor
Definition
A receptor that contains a binding site for a neurotransmitter and an ion channel that opens up when a molecule of the neurotransmitter attaches to the binding site.
Ex. ACH
Term
Metabotrophic Receptors
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 metabotrophic receptor; conveys messages to other molecules when a ligand binds with an activates the receptor.
Term
Second Messenger
Definition
A chemical produced when 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
Four Major Types of Neurotransmitter-dependent ion channels
Definition
1. Sodium (Na+)
2. Potassium (K+)
3. Chloride (Cl-)
4. Calcium (Ca++)
Term
causes depolarization (EPSP)
Definition
Influx of Na+.....
Term
causes hyperpolarization (IPSP)
Definition
Efflux of K+....
Term
causes hyperpolarization (IPSP)
Definition
Influx of Cl-...
Term
activates enzyme.
Definition
Influx of Ca++...
Term
Excitatory Postsynaptic Potential (EPSP)
Definition
An excitatory depolarization of the post synaptic 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 re-entry of a neurotransmitter just liberate by a terminal button back through the presynaptic membrane, thus terminating the post synaptic 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 (ACHE)
Definition
The enzyme that destroys acetylcholine soon after it is liberated by the terminal buttons, thus terminating the postsynaptic 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
Autoreceptors
Definition
A receptor molecule located on a presynaptic neuron that responds to the neurotransmitter released by the neuron.
*May be part of a regulatory system that controls the amount of neurotransmitter that is released
Term
Presynaptic inhibinition
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 faciliation
Definition
The action of a presynaptic terminal button in an axoaxonic synapse; increase the amoutn of neurotransmitter released by the postsynaptic terminal button.
Term
Axonaxonic Synapse
Definition
Synapse between axons. They alter the amount of neurotransmitter released by the terminal buttons of the post synaptic axon.
Term
Dendrodentritic Synapse
Definition
Synapse between dendrite. Perform regulatory functions, perhaps helping to organize the activity of groups of neurons.
Term
Gap Junction
Definition
A special junction between cells that permits direct communication by means of electrical grouping - electrical synapse.
Term
Neuromodulators
Definition
A naturally secreted substance that acts like a neurotransmitter except that 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
Hormones
Definition
A chemical substance that is released by an endocrine gland that has effects on target cells in other organs.
Term
Endocrine Glands
Definition
A gland that liberates it secretions into the extra cellular fluid around capillaries and hence into the blood stream.
Term
Target Cells
Definition
The type of cell that is directly affected by a hormone or other chemical signal.
Term
Steroid
Definition
A chemical of low molecular weight, derived from cholesterol. This hormone affects their target cells by attaching to receptors found within the nucleus
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