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biopsych ch3


absolute refractory phase a brief period of complete insensitivity to stimuli
acetylcholine (Ach) a neurotransmitter produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain
action potential the propogated electrical message of a neuron that travels along the axon to the presynaptic axon terminals
afterpotential the positive or negative change in membrane potential that may follow an action potential
agonist a molecule, usually a drug, that binds a receptor molecule and initiates a respone like that of another molecule, usually a neurotransmitter
all-or-none property the fact that the amplitude of the action potential is independent of the magnitude of the stimulus
anion a negatively charged ion, such as a protein or chloride ion
antagonist a molecule, usually a drug, that interferes with or prevents the action of a transmitter
aura in epilepsy, the unusual sensation or premonition that may precede the beginning of a seizure
axo-axonic referring to a synapse in which a presynaptic axon terminal synapses onto another axon's terminal
axo-somatic referring to a synapse in which a presynaptic axon terminal synapses onto the cell body (soma) of the postsynaptic neuron
batrachotoxin a toxin, produced by poison arrow frogs, that selectively interferes with Na channels
bungarotoxin a neurotoxin, isolated from the venom of the banded krait, that selectivly blocks acetylcholine receptors
cation a positively charged ion, such as a potassium or sodium ion
cell membrane the lipid bilayer that ensheathes a cell
channelopathy a genetic abnormality of ion channels, causing a variety of symptoms
chloride ion (Cl-) a chlorine atom that carries a negative charge because it has gained one electron
cholinergic referring to cells that use actylcholine as their synaptic transmitter
complex partial seizure in epilepsy, a type of seizure that doesn't involve the entire brain, and therefore can cause a wide variety of symptoms
concentration gradient variation of the concentration of a substance within a region
conduction velocity the speed at which an action potential is propagated along the length of an axon
convergence the phenomenon of neural connections in which many cells send signals to a single cell
curare an alkaloid neurotoxin that causes paralysis by blocking acetylcholine receptors in muscle
degradation the chemical breakdown of a neurotransmitter into inactive metabolites
dendro-dendritic referring to a type of synapse in which a synaptic connection forms between the dendrites of two neurons
depolarization a reduction in membrane potential (the interior of the neuron becomes less negative)
diffusion the spontanuous spread of molecules of one substance among molecules or another substance until a uniform concentration is achieved
divergence the phenomenon of neural connections in which one cell sends signals to many other cells
down-regulation a compensatory reduction in receptor availability at the synapses of a neuron
ectopic transmission cell-cell communication based on release of neurotransmitter in regions outside traditional synapses
electrical synapse gap junction' the region between neurons where the presynaptic and postsynaptic membranes are so close that the action potential can jump to the postsynaptic membrane without first being translated into a chemical message
electroencephalogram a recording of gross electrical activity of the brain recorded from large electrodes placed on the scalp
electrostatic pressure the propensity of charged molecules or ions to move, via diffusion, toward areas with the opposite charge
endogenous ligand any substance, produced with the body, that selectively binds to the type of receptor that is under study
epilepsy a brain disorder marked by major sudden changes in the electrophysiological state of the brain that are referred to as seizures
equilibrium here, the point at which the movement of ions across the cell membrane is balanced, as the electrostatic pressure pulling ions in one direction is offset by the diffusion force pushing them in the opposite direction
event-related potential (ERP) evoked potential' averaged EEG recordings measuring brain responses to repeated presentations of a stimulus. Components of the ERP tend to be reliable because the background noise of the cortex has been averaged out
excitatory postsynaptic potential (EPSP) a depolarizing potential in the postsynaptic neuron that is caused by excitory presynaptic potentials. EPSPs increase the probability that the postsynaptic neuron will fire an action potential
exogenous ligand any substance, originating from outside the body, that selectively binds to the type of receptor that is under study
extracellular fluid the fluid in the spaces between cells (interstitial fluid) and in the vascular system
G proteins a class of proteins that reside next to the intracellular portion of a receptor and that are activated when the receptor binds an appropriate ligand on the extracellular surface
gated referring to the property by which an ion channel may be opened or closed by factors such as chemicals, voltage changes, or mechanical actions
grand mal seizure type of generalized epileptic seizure in which nerve cells fire in high-frequency bursts
hyperpolarization increase in membrane potential (the interior of the neuron becomes even more negative
inhibitory postsynaptic potential (IPSP) a hyperpolarizing potential in the postsynaptic neuron that is caused by inhibitory connections. IPSPs decrease the probability that the postsynaptic neuron will fire an action potential
intracellular fluid cytoplasm' watery solution found within the cells
ion channel pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open
ion an atom or molecule that has acquired an electrical charge by gaining or losing one or more elections
ionotropic receptor a receptor protein that includes an ion channel that is opened when the receptor is bound by an appropriate ligand
kindling a method of experimentally inducing an epileptic seizure by repeatedly stimulating a brain region
knee jerk reflex a variant of the stretch reflex in which stretching of the tendon beneath the knee leads to an upward kick of the leg
ligand a substance that binds to receptor molecules, such as those at the surface of the cell
ligand-gated ion channel aka: chemically gated ion channel. An ion channel that opens or closes in response to the presence of a particular chemical
lipid bilayer the structure of the neuronal cell membrane, which consists of two layers of lipid molecules, within float various specialized proteins, such as receptors
local potential an electrical potential that is initiated by stimulation at a specific site, which is a graded response that spreads passively across the cell membrane, decreasing in strength with time and distance
metabotropic receptor receptor protein that does not contain an ion channel but may, when activated, use a G protein system to alter the functioning of the postsynaptic cell
microelectrode an especially small electrode used to record electrical potentials from living cells
millivolt (mV) thousandth of a volt
negative polarity negative electrical-potential difference relative to a reference electrode
Nernst equation an equation predicting the voltage needed to just counterbalance the diffusion force pushin an ion across a semipermeable membrane from the side with a high concentration to the side with a low concentration
neural chain simple kind of neural circuit in which neurons are attached linearly, end-to-end
neurophysiology the study of the life processes of neurons
neurotransmitter synaptic transmitter, chemical transmitter, or simply transmitter' the chemical released from the presynaptic axon terminal that serves as the basis of communication between neurons
node of Ranvier gap between successive segments of the myelin sheath where the axon membrane is exposed
nondirected synapse a type of synapse in which the presynaptic and postsynaptic cells are not in close apposition; instead, neurotransmitter is released by axonal varicosities and diffuses away to affect wide regions of tissue
petit mal seizure absence attack' a seizure that is characterized by a spike-and-wave EEG and often involves a loss of awareness and inability to recall events surrounding the seizure
pinocytosis the process by which synaptic neurotransmitter is repackaged into synaptic vesicles
postsynaptic potential local potential that is initiated by stimulation at a synapse, can vary in amplitude, and spreads passively acreoss the cell membrane, decreasing in strength with time and distance
potassium ion (K ) potassium ion that carries a positive charge because it has lost one electron
receptor molecule receptor' protein that captures and reacts to molecules of a neurotransmitter or hormone
refractory transiently inactivated or exhausted
relative refractory phase period of reduced sensitivity during which only strong stimulation produces an action potential
resting membrane potential a difference in electrical potential across the membrane of a nerve cell during an inactive period
retrograde synanpse a synapse in which a signal (usually a gas neurotransmitter) flows from the postsynaptic neuron to the presynaptic neuron, thus counter to the usual direction of synaptic communication
reuptake the process by which released synaptic transmitter molecules are taken up and reused by the presynaptic neuron, thus stopping synaptic activity
saltatory conduction the form of conduction that is characteristic of myelinated axons, in which the action potential jums from one node of Ranvier to the next
saxitoxin (STX) an animal toxin that blocks sodium channels when applied to the outer surface of the cell membrane
second messenger a slow-acting substance in the postsynaptic cell that amplifies the effects of synaptic activity and signal synaptic activity within the postsynaptic cell
seizure an epileptic episode
selective permeabilty the property of a membrane that allows some substances to pass through, but not others
sodium ion (Na ) a sodium ion that carries a positive charge because it has lost one electron
sodium-potassium pump the energetically expensive mechanism that pushes sodium ions out of a cell, and potassium ions in
spatial summation summation at the axon hillock of postsynaptic potentials from across the cell body. If this summation reaches threshold, an action potential is triggered
synaptic delay the brief delay between the arrival of an action potential at the axon terminal and the creation of a postsynaptic potential
temporal summation the summation of postsynaptic potential that reach the axon hillock at different times. The closer in time that the potential occur, the more complete the summation
tetrodotoxin (TTX) a toxin from puffer fish ovaries that blocks the voltage-gated soduim channel, preventing action potential conduction
threshold the stimulus intensity that is just adequate to trigger an action potential at the axon hillock
transporters specialized receptors in the presynaptic membrane that recognize transmitter molecules and return them to the presynaptic neuron for reuse
up-regulation a compensatory increase in receptor availability at the synapses of a neuron
varicosity the axonal swelling from which neurotransmitter diffuses in a nondirected synapse
voltage-gated Na channel a Na selective channel that opens or closes in response to changes in the voltage of the local membrane protential; it mediates the action potential
Created by: laurilayne68
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