Chapter 3 (Neurophysiology) Flashcards
neurophysiology
The study of the life processes of neurons
polarized
Exhibiting difference in electrical charge between the inside and outside of the cell.
ion
An atom or molecule that has acquired electrical charge by gaining or losing one or more electrons
anion
a negatively charged ion, such as a protein or chloride ion
cation
a positively charged ion, such as a potassium or sodium ion
intracellular fluid
Also called cytoplasm. The watery solution found within cells.
extracellular fluid
The fluid in the spaces between cells (interstitial fluid) and the vascular system
cell membrane
The lipid bilayer that ensheathes a cell
microelectrode
An especially small electrode used to record electrical potentials in living cells.
resting potential
A difference in electrical potential across the membrane of a nerve cell during an inactive period.
millivolt (mV)
A thousandth of a volt.
ion channel
A pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open
potassium ion (K+)
a potassium atom that carries a positive charge because it has lost one electron.
selective permeability
The property of a membrane that allows some substances to pass through, but not others.
diffusion
The spontaneous spread of molecules untili a uniform concentration is achieved.
electrostatic pressure
The propensity of charged molecules or ions to move, via diffusion, toward areas with the opposite charge
sodium-potassium pump
The energetically expensive mechanism that pushes sodium ions out of a cell, and potassium ions in.
sodium ion (Na+)
A sodium atom that carries a positive charge because it has lost one electron
equilibrium potential
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.
axon hillock
The cone-shaped area on the cell body from which the axon originates
hyperpolarization
An increase in membrane potential (the interior of the neuron becomes even more negative).
depolarization
A decrease in membrane potential (the interior of the neuron becomes less negative).
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
threshold
The stimulus intensity that is just adequate to trigger an action potential at the axon hillock
action potential
Also called spike. A rapid reversal of the membrane potential that momentarily makes the inside of the membrane positive with respect to the outside
all-or-none property
The fact that the size (amplitude) of the action potential is independent of the size of the stimulus.
afterpotential
The positive or negative change in membrane potential that may follow an action potential
voltage-gated Na+ channel
A Na+ selective channel that opens or closes in response to changes in the voltage of the local membrane potential; it mediates teh action potential
refractory
temporarily unresponsive or inactivated
absolute refractory phase
A brief period of complete insensitivity to stimuli
relative refractory phase
A period of reduced stimulation during which only strong stimulation produces an action potential
conduction velocity
The speed at which an action potential is propagated along the length of an axon (or section of peripheral nerve).
myelin
The fatty insulation around an axon, formed by glial cells. This sheath boosts the speed at which nerve impulses are conducted.
node of Ranvier
A gap between successive segments of the myelin sheath where the axon membrane is exposed.
saltatory conduction
The form of conduction that is characteristic of myelinated axons, in which the action potential jumps from one node of Ranvier to the next.
postsynaptic potential
A local potential that is initiated by a stimulation at a synapse, which can vary in amplitude, and spreads passively across the cell membrane, decreasing in strength with time and distance.
EPSP
A depolarizing potential in the postsynaptic neuron that is caused by excitatory presynaptic potentials. EPSPs increase the probability that the postsynaptic neuron will fire an action potential.
synaptic delay
The brief delay between the arrival of an action potential at the axon terminal adn the creation of a post-synaptic 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.
chloride ion (Cl-)
A chlorine atom that carries a negative charge because it has gained one electron.
spatial summation
The summation of postsynaptic potentials that reach the axon hillock from different locations across the cell body. If this summation reaches threshold, an action potential is triggered.
temporal summation
The summation of postsynaptic potentials that reach the axon hillock at different times. The closer in time the potentials occur, the more complete the summation is.
synaptic vesicle
A small, spherical structure that contains molecules of neurotransmitter
calcium ion (Ca2+)
a calcium atom that carries a double positive charge because it has lost two electrons
ligand
a substance that binds to receptor molecules, such as a neurotransmitter or drug that binds postsynaptic receptors
acetylcholine (ACh)
A neurotransmitter that is produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain.
curare
a neurotoxin that causes paralysis by blocking ACh receptors in muscle.
bungarotoxin
A neurotoxin, isolated form the venom of the banded krait, that selectively blocks ACh receptors.
agonist
A molecule, usually a drug, that binds a receptor molecule and initiates a response like that of another molecule, usually a neurotransmitter
antagonist
A molecule, usually a drug, that interferes with or prevents the action of a neurotransmitter
cholinergic
Referring to cells that use ACh as their synaptic transmitter.
degradation
The chemical breakdown of a neurotransmitter into inactive metabolics
acetylcholinesterase (AChE)
An enzyme that inactivates the transmitter ACh
reuptake
The process by which release transmitter molecules are taken up and reused by the presynaptic neuron, thus stopping synaptic activity.
transporter
A specialized receptor in the presynaptic membrane that recognizes transmitter molecules and returns them to the presynaptic neuron for reuse.
knee jerk reflex
A variant of the stretch reflex in which stretching the tendon beneath the knee leads to an upward kick of the leg
electroencephalogram (EEG)
A recording of gross electrical activity of the brain via large electrodes placed on the scalp.
event-related potential (ERP)
Also called 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.
epilepsy
A brain disorder marked by major, suden changes in the electrophysical state of the brain that are referred to as seizures.
seizure
an epileptic episode
grand mal seizure
A type of generalized epileptic seizure in which nerve cells fire in high-frequency bursts, usually accompanied by involuntary rhythmic contractions of the body
petit mal seizure
Also called 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.
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
aura
In epilepsy, the unusual sensations or premonition that may precede the beginning of a seizure.
