chapter 3: neurophysiology Flashcards
Neurophysiology
The study of the life processes of neurons
Polarized
Exhibiting a difference in electrical charge between the inside and outside of the cell
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 a chloride ion
Cation
A positively charged ion, such as a potassium or sodium ion
Intracellular fluid
The watery solution found within cells
Also called cytoplasm
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 in living cells
Resting potential
A difference in electrical potential across the membrane of a nerve cell during an inactive period
Ion channel
A pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open
Millivolt (mV)
A thousandth of a volt
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 until 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
An increase 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
A rapid reversal of the membrane potential that momentarily makes the inside of the membrane positive with respect to the outside
Also called spike
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 the action potential
Refractory
Temporarily unresponsive or inactivated