Ch 2: Structure and Functions of Cells of the Nervous System. Flashcards
Sensory Neuron
A neuron that detects changes in the external or internal environment and sends information about these changes to the central nervous system.
Motor Neuron
A neuron located within the central nervous system that controls the contraction of a muscle or the secretion of a gland.
Interneuron
A neuron located entirely within the central nervous system.
Central Nervous System (CNS)
The brain and spinal cord.
Peripheral Nervous System (PNS)
The part of the nervous system outside the brain and spinal cord, including the nerves attached to the brain and spinal cord.
Soma
The cell body of a neuron, which contains the nucleus.
Dendrite
A branched, treelike structure attached to the soma of a neuron; receives information from the terminal buttons of other neurons.
Synapse
A junction between the terminal button of an axon and the membrane of another neuron.
Axon
The long, thin, cylindrical structure that conveys information from the soma of a neuron to its terminal buttons.
Multipolar Neuron
A neuron with one axon and many dendrites attached to its soma.
Unipolar Neuron
A neuron with one axon attached to its soma; the axon divides, with one branch receiving sensory information and the other sending the information into the central nervous system.
Terminal Button
The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to the neuron.
Neurotransmitter
A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron.
Membrane
A structure consisting principally of lipid molecules that defines the outer boundaries of a cell and also constitutes many of the cell organelles, such as the Golgi apparatus.
Nucleus
A structure in the central region of a cell, containing the nucleolus and chromosomes.
Nucleolus (new clee o lus)
A structure within the nucleus of a cell that produces the ribosomes.
Ribosome
A cytoplasmic structure, made of protein, that serves as the site of production of proteins translated from mRNA.
Chromosome
A strand of DNA, with associated proteins, found in the nucleus; carries genetic information.
Deoxyribonucleic Acid (DNA)
A long, complex macromolecule consisting of two interconnected helical strands; along with associated proteins, strands of DNA constitute the chromosomes.
Gene
The functional unit of the chromosome, which directs synthesis of one or more proteins.
Messenger Ribonucleic Acid (mRNA)
A macromolecule that delivers genetic information concerning the synthesis of a protein from a portion of a chromosome to a ribosome.
Enzyme
A molecule that controls a chemical reaction, combining two substances or breaking a substance into two parts.
Non-coding RNA (ncRNA)
A form of RNA that does not encode for protein but has functions of its own.
Cytoplasm
The viscous, semiliquid substance contained in the interior of a cell.
Mitochondrion
An organelle that is responsible for extracting energy from nutrients.
Adenosine Triphosphate (ATP) [ah den o seen]
A molecule of prime importance to cellular energy metabolism; its breakdown liberates energy.
Endoplasmic Reticulum
Parallel layers of membrane found within the cytoplasm of a cell. Rough endoplasmic reticulum contains ribosomes and is involved with production of proteins that are secreted by the cell. Smooth endoplasmic reticulum is the site of synthesis of lipids and provides channels for the segregation of molecules involved in various cellular processes.
Golgi Apparatus
A complex of parallel membranes in the cytoplasm that wraps the products of a secretory cell.
Exocytosis
The secretion of a substance by a cell through means of vesicles; the process by which neurotransmitters are secreted.
Lysosome
An organelle surrounded by membrane; contains enzymes that break down waste products.
Cytoskeleton
Formed of microtubules and other protein fibers, linked to each other and forming a cohesive mass that gives a cell its shape.
Microtubule
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.
Axoplasmic Transport
An active process by which substances are propelled along microtubules that run the length of the axon.
Anterograde
In a direction along an axon from the cell body toward the terminal buttons.
Retrograde
In a direction along an axon from the terminal buttons toward the cell body.
Glia (glee ah)
The supporting cells of the CNS
Astrocyte
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.
Phagocytosis (fagg o sy toe sis)
The process by which cells engulf and digest other cells or debris caused by cellular degeneration.
Oligodendrocyte
A type of glial cell in the central nervous system that forms myelin sheaths.
Myelin Sheath
A sheath that surrounds axons and insulates them, preventing messages from spreading between adjacent axons.
Node of Ranvier
A naked portion of myelinated axon between adjacent oligodendroglia or Schwann cells.
Microglia
The smallest of glial cells; act as phagocytes and protect the brain from invading microorganisms.
Schwann Cell
A cell in the peripheral nervous system that is wrapped around a myelinated axon, providing one segment of its myelin sheath.
Blood-brain Barrier
A semipermeable barrier between the blood and the brain produced by the cells in the walls of the brain’s capillaries.
Area Postrema
A region of the medulla where the blood-brain barrier is weak; poisons can be detected there and can initiate vomiting.
Electrode
A conductive medium that can be used to apply electrical stimulation or to record electrical potentials.
Microelectrode
A very fine electrode, generally used to record activity of individual neurons.
Membrane Potential
The electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell.
Oscilloscope
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.
Resting Potential
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.
Depolarization
Reduction (toward zero) of the membrane potential of a cell from its normal resting potential.
Hyperpolarization
An increase in the membrane potential of a cell, relative to the normal resting potential.
Action Potential
The brief electrical impulse that provides the basis for conduction of information along an axon.
Threshold of Excitation
The value of the membrane potential that must be reached to produce an action potential.
Diffusion
Movement of molecules from regions of high concentration to regions of low concentration.
Electrolyte
An aqueous solution of a material that ionizes - namely, a soluble acid, base, or salt.
Ion
A charged molecule. Cations are positively charged, and anions are negatively charged.
Electrostatic Pressure
The attractive force between atomic particles charged with opposite signs of the repulsive force between atomic particles charged with the same sign.
Intracellular Fluid
The fluid contained within cells.
Extracellular Fluid
Body fluids located outside of the cell.
Sodium-potassium Transporter
A protein found in the membrane of all cells that extrude sodium ions from and transports potassium ions into the cell.
Ion Channel
A specialized protein molecule that permits specific ions to enter or leave cells.
Voltage-dependent Ion Channel
An ion channel that opens or closes according to the value of the membrane potential.
All-or-none Law
The principle that once an action potential is triggered in an axon, it is propagated, without decrement, to the end of the fiber.
Rate Law
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 that axon fires.
Saltatory Conduction
Conduction of action potentials by myelinated axons. The action potential appears to jump from one node of Ranvier to the next.
Postsynaptic Potential
Alterations in the membrane potential of a postsynaptic neuron, produced by liberation of neurotransmitters at the synapse.
Binding Site
The location on a receptor protein which a ligand binds.
Ligand
A chemical that binds with the binding site of a receptor.
Dendritic Spine
A small bud on the surface of a dendrite, with which a terminal button of another neuron forms a synapse.
Presynaptic Membrane
The membrane of a terminal button that lies adjacent to the postsynaptic membrane and through which the neurotransmitter is released.
Postsynaptic Membrane
The cell membrane opposite the terminal button in a synapse; the membrane of a cell that receives the message.
Synaptic Cleft
The space between the presynaptic membrane and the postsynaptic membrane.
Synaptic Vesicle
A small, hollow, beadlike structure found in terminal buttons; contains molecules of a neurotransmitter.
Release Zone
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.
Postsynaptic Receptor
A receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter.
Neurotransmitter-dependent Ion Channel
An ion channel that opens when a molecule of a neurotransmitter binds with a postsynaptic receptor.
Ionotropic Receptor
A receptor that contains a binding site for a neurotransmitter and an ion channel that opens when a molecule of the neurotransmitter attaches to the binding site.
Metabotropic Receptor
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.
G Protein
A protein coupled to a metabotropic receptor; conveys messages to other molecules when a ligand binds with and activates the receptor.
Second Messenger
A chemical produced when a G protein activates an enzyme; carries a signal that results in the opening of the ion channel of causes other events to occur in the cell.
Excitatory Postsynaptic Potential (EPSP)
An excitatory depolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button.
Inhibitory Postsynaptic Potential (IPSP)
An inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button.
Reuptake
The reentry of a neurotransmitter just liberated by a terminal button back through its membrane, thus terminating the postsynaptic potential.
Enzymatic Deactivation
The destruction of a neurotransmitter by an enzyme after its release - for example, the destruction of acetylcholine by acetylcholinesterase.
Acetylcholine (ACh)
A neurotransmitter found in the brain, spinal cord, and parts of the PNS; responsible for muscular contraction.
Acetylcholinesterase (AChE)
The enzyme that destroys acetylcholine soon after it is liberated by the terminal buttons, thus terminating the postsynaptic potential.
Neural Integration
The process by which inhibitory and excitatory postsynaptic potentials summate and control the rate of firing of a neuron.
Autoreceptor
A receptor molecule located on a neuron that responds to the neurotransmitter released by that neuron.
Presynaptic Inhibition
The action of a presynaptic terminal button in an axoaxonic synapse; reduces the amount of neurotransmitters released by the postsynaptic terminal buttons.
Presynaptic Facilitation
The action of a presynaptic terminal button in an axoaxonic synapse; increases the amount of neurotransmitters released by the postsynaptic terminal button.
Gap Junction
A special junction between cells that permits direct communication by means of electrical coupling.
Neuromodulator
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.
Peptide
A chain of amino acids joined together by peptide bonds. Most neuromodulators, and some hormones, consist of peptide bonds.
Hormone
A chemical substance that is released by an endocrine gland that has effects on target cells in other organs.
Endocrine Gland
A gland that liberates its secretions into the extracellular fluid around capillaries and hence into the bloodstream.
Target Cell
The type of that is directly affected by a hormone or other chemical signal.
Steroid
A chemical of low molecular weight, derived from cholesterol. Steroid hormones affect their target cells by attaching to receptors found within the nucleus.
