CN - Chapter 3 - The Neuronal Membrane at Rest

Question 1

action potential

Answer 1

A brief fluctuation in membrane potential caused by the rapid opening and closing of voltage-gated ion channels;

also known as spike, nerve impulse, or discharge.

Action potentials sweep like a wave along axons to transfer information from one place to another in the nervous system.

Question 2

excitable membrane

Answer 2

Any membrane capable of generating action potentials.

The membrane of axons and muscle cells is excitable.

Question 3

resting membrane potential

Answer 3

The membrane potential, or membrane voltage, maintained by a cell when it is not generating action potentials;

also called resting potential.

Neurons have a resting membrane potential of about -65 mV.

Question 4

ion

Answer 4

An atom or molecule that has a net electrical charge because of a difference in the number of electrons and protons.

Question 5

cation

Answer 5

A positively charged ion. (See also anion).

Question 6

anion

Answer 6

A negatively charged ion. (See also cation).

Question 7

phospholipid bilayer

Answer 7

The arrangement of phospholipid molecules that forms the basic structure of the cell membrane.

The core of the bilayer is lipid, creating a barrier to water and to water-soluble ions and molecules.

Question 8

peptide bond

Answer 8

The covalent bond between the amino group of one amino acid and the carboxyl group of another.

Question 9

polypeptide

Answer 9

A string of amino acids held together by peptide bonds.

Question 10

ion channel

Answer 10

A membrane-spanning protein that forms a pore that allows the passage of ions from one side of the membrane to the other.

Question 11

ion selectivity

Answer 11

A property of ion channels that are selectively permeable to some ions and not to others.

Question 12

gating

Answer 12

A property of many ion channels, making them open or closed in response to specific signals, such as membrane voltage or the presence of neurotransmitters.

Question 13

ion pump

Answer 13

A protein that ransports ions across a membrane at the expense of metabolic energy.

Question 14

diffusion

Answer 14

The temperature-dependent movement of molecules from regions of high concentration to regions of low concentration, resulting in a more even distribution.

Question 15

concentration gradient

Answer 15

A difference in concentration from one region to another.

Ionic concentration gradients across the neuronal membrane help determine the membrane potential.

Question 16

electrical curent

Answer 16

The rate of movement of electrical charge, represented by the symbol I and measured in amperes (amp).

Question 17

voltage

Answer 17

The force exerted on an electrically charged particle, represented by the symbol V and measured in volts;

also called electrical potential or potential difference.

Question 18

electrical conductance

Answer 18

The relative ability of an electrical charge to migrate from one point to another, represented by the symbol g and measured in siemens (S).

Conductance is the inverse of resistance and is related to electrical current and voltage by Ohm’s law.

Question 19

electrical resistance

Answer 19

The relative inability of an electrical charge to migrate from one point to another, represented by the symbol R and measured in ohms (W).

Resistance is the inverse of conductance and is related to electrical current and voltage by Ohm’s law.

Question 20

Ohm’s law

Answer 20

The relationship between electrical current (I), voltage (V), and conductance (g):

I = gV

Because electrical conductance is the inverse of resistance (R), Ohm’s law may also be written:

V = IR

Question 21

membrane potential

Answer 21

The voltage across a cell membrane;

represented by the symbol Vm.

Question 22

microelectrode

Answer 22

A probe used to measure the electrical activity of cells.

Microelectrodes have a very fine tip and can be fashioned from etched metal or glass pipettes filled with electrically conductive solutions.

Question 23

ionic equilibrium potential

(equilibrium potential)

Answer 23

The electrical potential difference that exactly balances an ionic concentration gradient, represented by the symbol E_ion

Also known as equilibrium potential.

Question 24

ionic driving force

Answer 24

The difference between the real membrane potential, V_m, and the ionic equilibrium potential E_ion.

Question 25

Nernst equation

Answer 25

A mathematical relationship used to calculate an ionic equilibrium potential.

Question 26

sodium-potassium pump

Answer 26

An ion pump that removes intracellular Na⁺ and concentrates intracellular K⁺, using adenosine triphosphate as its energy source.

Question 27

calcium pump

Answer 27

An ion pump that removes cytosolic Ca²⁺.

Question 28

Goldman equation

Answer 28

A mathematical relationship used to predict membrane potential from the concentrations and membrane permeabilities of ions.

Question 29

depolarization

Answer 29

A change in membrane potential, taking it from the value at rest (e.g., -65 mV) to a less negative value (e.g., 0 mV).

Question 30

blood-brain barrier

Answer 30

A specialization of the walls of brain capillaries that limits the movement of blood-bourne substances into the extracellular fluid of the brain.