Behavioral Neuroscience: Chapter 3

Front 1

Neurophysiology

Back 1

The study of the life processes of neurons.

Front 2

Ion

Back 2

An atom or molecule that has acquired an electrical charge by gaining or losing one or more electrons.

Front 3

Anion

Back 3

A negatively charged ion, such as a protein or chloride ion.

Front 4

Cation

Back 4

A positively charged ion, such as a potassium or sodium ion.

Front 5

Intracellular fluid

Back 5

Also called cytoplasm. The watery solution found within cells.

Front 6

Extracellular fluid

Back 6

The fluid in the spaces between cells (interstitial fluid) and in the vascular system.

Front 7

Cell membrane

Back 7

The lipid bilayer that ensheathes a cell.

Front 8

Microelectrode

Back 8

An especially small electrode used to record electrical potentials from living cells.

Front 9

Resting membrane potential

Back 9

A difference in electrical potential across the membrane of a nerve cell during an inactive period.

Front 10

Millivolt (mV)

Back 10

A thousandth of a volt.

Front 11

Negative polarity

Back 11

A negative electrical potential difference relative to a reference electrode.

Front 12

Lipid bilayer

Back 12

The structure of the neuronal cell membrane, which consists of two layers of lipid molecules, within which float various specialized proteins, such as receptors.

Front 13

Ion channel

Back 13

A pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open.

Front 14

Potassium ion (K+)

Back 14

A potassium atom that carries a positive charge because it has lost one electron.

Front 15

Selective permeability

Back 15

The property of a membrane that allows some substances to pass through the membrane when the channels are open.

Front 16

Diffusion

Back 16

The spontaneous spread of molecules that allow some substances to pass through, but not others.

Front 17

Concentration gradient

Back 17

Variation of the concentration of a substance within a region.

Front 18

Electrostatic pressure

Back 18

The propensity of charged molecules or ions to move, via diffusion, toward areas with the opposite charge.

Front 19

Sodium-potassium pump

Back 19

The energetically expensive mechanism that pushes sodium ions out of a cell and potassium ions in.

Front 20

Sodium ion (Na+)

Back 20

A sodium atom that carries a positive charge because it has lost one electron.

Front 21

Equilibrium

Back 21

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.

Front 22

Nernst equation

Back 22

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.

Front 23

Action potential

Back 23

The propagated electrical message of a neuron that travels along the axon to the presynaptic axon terminals.

Front 24

Hyperpolarization

Back 24

An increase in membrane potential (the interior of the neuron becomes even more negative).

Front 25

Depolarization

Back 25

A reduction in the membrane potential (the interior of the neuron becomes less negative).

Front 26

Local potential

Back 26

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.

Front 27

Threshold

Back 27

The stimulus intensity that is just adequate to trigger an action potential.

Front 28

All-or-none property

Back 28

The fact that amplitude of the action potential is independent of the magnitude of the stimulus.

Front 29

Afterpotential

Back 29

The positive or negative change in membrane potential that may follow an action potential.

Front 30

Voltage-gated Na+ channel

Back 30

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.

Front 31

Refractory

Back 31

Transiently inactivated or exhausted.

Front 32

Absolute refractory phase

Back 32

A brief period of complete insensitivity to stimuli.

Front 33

Relative refractory phase

Back 33

A period of reduced sensitivity during which only strong stimulation produces an action potential.

Front 34

Channelopathy

Back 34

A genetic abnormality of ion channels, causing a variety of symptoms.

Front 35

Tetrodotoxin (TTX)

Back 35

A toxin from puffer fish ovaries that blocks the voltage-gated sodium channel, preventing action potential conduction.

Front 36

Saxitoxin (STX)

Back 36

An animal toxin that blocks sodium channels when applied to the outer surface of the cell membrane.

Front 37

Batrachotoxin

Back 37

A toxin, secreted by poison arrow frogs, that selectively interferes with Na+ channels.

Front 38

Conduction velocity

Back 38

The speed at which an action potential is propagated along the length of an axon, or section of peripheral nerve.

Front 39

Node of Ranvier

Back 39

A gap between successive segments of myelin sheath where the axon membrane is exposed.

Front 40

Saltatory conduction

Back 40

The form of conduction that is characteristic of myelinated axons, in which the action potential jumps from one node of Ranvier to the next.

Front 41

Neurotransmitter

Back 41

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.

Front 42

Postsynaptic potential

Back 42

A local potential that is initiated by stimulation at a synapse, can vary in amplitude, and spreads passively across the cell membrane, decreasing in strength with time and distance.

Front 43

Excitatory postsynaptic potential (EPSP)

Back 43

A depolarizing potential in the postsynaptic neuron that is caused by excitatory connections. EPSPs increase the probability that the postsynaptic neuron will fire an action potential.

Front 44

Synaptic delay

Back 44

The brief delay between the arrival of an action potential at the axon terminal and the creation of a postsynaptic potential.

Front 45

Inhibitory postsynaptic potential (IPSP)

Back 45

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.

Front 46

Chloride ion (Cl-)

Back 46

A chlorine atom that carries a negative charge because it has gained one electron.

Front 47

Spatial summation

Back 47

The summation of postsynaptic potentials that reach the axon hillock of postsynaptic potentials from across the cell body. If this summation reaches the threshold, an action potential is triggered.

Front 48

Temporal summation

Back 48

The summation of postsynaptic potentials that reach the axon hillock at different times. The closer in time that potentials occur, the more complete the summation.