B2-Structure and Functions of Cells of the Nervous System Flashcards
Motor neuron
A neuron located within the central nervous system that controls the contraction of a muscle or the secretion of a gland
Sensory neuron
A neuron that detects change in the external or internal environmental and sends information about these changes to the central nervous system
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 form the soma of a neuron to its terminal buttons
Multipolar neuron
A neuron with one axon and many dendrites attached to its soma
Bipolar neuron
A neuron with one axon and one dendrite attached to its soma
Unipolar neuron
A neuron with one axon attached to it soma; the axon divides with the 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 send information to that 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
Cytoplasm
The viscous, semiliquid substance contained in the interior of a cell
Mitochondria
And organelle that is responsible for extracting energy from nutrients
Adenosine triphosphate (ATP)
A molecule of prime importance to cellular energy metabolism; it’s breakdown liberates energy
Nucleus
A structure in the central region of a cell, containing the chromosomes
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
Cytoskeleton
Support structure formed of microtubules and other protein fibers that are linked to each other and form a cohesive mass that gives a cell it’s shape
Enzyme
A molecule that controls a chemical reaction, combining two substances or breaking a substance into two parts
Axoplasmic transport
An active process by which substances are propelled along microtubules that run the length of the axon
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
Glia
The supporting cells of the central nervous system
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
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 a myelinated axon, between adjacent oligodendroglia or Schwann cells
Microglia
The smallest of glial cells; they 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 70 mV 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 the cell relative to the normal resting potential
Action potential
The brief electrical impulse that provides a basis for conduction of information along the axon
Threshold of excitation
The value of the membrane potential that must be reached to produce action
Diffusion
Movement of molecules from regions of high concentration two 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 or the repulsive force between atomic particles charge with the same sign
Intracellular fluid
The fluid contained within cells
Extracellular fluid
Body fluids located outside of cells
Sodium-potassium transporter
A proteins found in the membrane of all cells that extrudes 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 the axon fires
Saltatory conduction
Conduction of action potentials by Myelinated axons. The action potential appear 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 neurotransmitter at the synapse
Binding site
The location on a receptor protein to which the ligand binds
Ligand
A chemical that binds with the binding site of a receptor
Dendritic spine
A small bud on the surface of the dendrite with which the terminal button of another neuron forms a synapse
Presynaptic membrane
The membrane of the terminal button that lies adjacent to the postsynaptic membrane and through which the neurotransmitter is released
Synaptic cleft
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
The 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 attached 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 cell’s membrane when a molecule of the neurotransmitter attaches to the binding site
G protein
A protein coupled to the 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 or 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)
And inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused 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 it’s release-for example the destruction of acetylcholine by acetylcholinesterase
Acetylcholine (ACh)
A neurotransmitter found in the brain, spinal cord, and parts of the peripheral nervous system; responsible for muscular contradiction
Acetylcholinesterase (AChE)
The enzyme that destroys acetylcholine soon after it is liberated from 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 neurotransmitter released by the postsynaptic terminal button
Presynaptic facilitation
The action of a presynaptic terminal button in an axoaxonic synapse; increases the amount of neuraltransmitter released by the postsynaptic terminal button
Neuromodulator
A naturally secreted substance that acts like a neurotransmitter except that it is not restricted to the synaptic cleft but diffused through the extracellular fluid
Peptide
A chain of amino acids joined together by peptide bonds. Most neuromodulators, and some hormones, consist of peptide molecules
Hormone
A chemical substance that is released by an endocrine gland and that has effects on target cells in other organs
Endocrine gland
A gland that liberates it’s secretions into the extracellular fluid around capillaries and hence into the bloodstream
Target cell
The type of cell that contains receptors for a particular hormone and is affected by that hormone
