3 - Neurophysiology: The Generation, Transmission, and Integration of Neural Signals Flashcards
Action potential
The propagated electrical message of a neuron that travels along the axon to the presynaptic axon terminals
Neurophysiology
The study of the life processes of neurons
Neurotransmitter
Also called synaptic transmitter, chemical transmitter, or simply transmitter. The chemical released from the presynaptic axon terminal that serves as the basis of communication between neurons
Ion
An atom or molecule that has acquired an 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 in the vascular system
Cell membrane
The lipid bilayer that ensheathes a cell
Microelectrode
An especially small electrode used to record electrical potentials from living cells
Resting membrane potential
A difference in electrical potential across the membrane of a nerve cell during an inactive period
Millivolt (mV)
A thousandth of a volt
Negative polarity
A negative electrical potential difference relative to a reference electrode
Lipid bilayer
The structure of the neuronal cell membrane, which consists of two layers of lipid molecules, within which floats various specialized proteins, such as receptors
Ion channel
A pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open
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
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 of one substance among molecules of another substance until a uniform concentration is achieved
Concentration gradient
Variation of the concentration of a substance within a region
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, a potassium ions in
Sodium ion (Na+)
A sodium atom that carries a positive charge because it has lost one electron
Equilibrium
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 opposite direction
Nernst equation
An equation predicting the voltage needed to just counterbalance the diffusion force pushing an ion across a semipermeable membrane from the side with a high concentration to the side with a low concentration
Axon hillock
A cone-shaped area from which the axon originates out of the cell body. Functionally, the integration zone of the neuron
Hyperpolarization
An increase in membrane potential (the interior of the neuron becomes even more negative).
Depolarization
A reduction 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
All-or-none property
The fact that the amplitude of the action potential is independent of the magnitude of the stimulus
Afterpotential
The positive or negative change in membrane potential that may follow an action potential
Voltage-gated/sodium activated Na+ channel
A Na+/- selective channel that opens or closes in response to changes in the voltage of the local membrane potential; it mediates the action potential
Refractory
Transiently inactivated or exhausted
Absolute refractory phase
A brief period of complete insensitivity to stimuli
Relative refractory phase
A period of reduced sensitivity during which only strong stimulation produces an action potential
Channelopathy
A genetic abnormality of ion channels, causing a variety of symptoms