Chapter 2.1

Question 1

Intracellular fluid/Cytoplasm

Answer 1

The watery solution found within cells

Question 2

Extracellular fluid/Interstitial fluid

Answer 2

The fluid in the spaces between cells

Question 3

Microelectrode

Answer 3

An especially small electrode used to record electrical potential inside living cells

Question 4

Resting potential

Answer 4

The difference in electrical potential across the membrane of a nerve cell at rest

Question 5

Millivolt (mV)

Answer 5

A thousandth of a volt

Question 6

Ion channel

Answer 6

A pore in the cell membrane that permits the passage of certain ions through the membrane when the channel is open

Question 7

Selective permeability

Answer 7

The property of a membrane that allows some substance to pass through, but not others

Question 8

Electrostatic pressure

Answer 8

The propensity of charged molecules or ions to move toward areas with the opposite charge

Question 9

Sodium-potassium pump

Answer 9

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

Question 10

Equilibrium potential

Answer 10

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

Question 11

Hyperpolarization

Answer 11

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

Question 12

Depolarization

Answer 12

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

Question 13

Local potential

Answer 13

An electrical potential that is initiated by stimulation at a specific site, is a graded response that spreads passively across the cell membrane, and decreases in strength with time and distance

Question 14

Threshold

Answer 14

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

Question 15

Action potential/Spike

Answer 15

A rapid reversal of the membrane potential that momentarily makes the inside of a neuron positive with respect to the outside

Question 16

All-or-none property

Answer 16

The condition that the size (amplitude) of the action potential is independent of the size of the stimulus

Question 17

Afterpotential

Answer 17

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

Question 18

Voltage-gated Na+ channel

Answer 18

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

Question 19

Refractory

Answer 19

Temporarily unresponsive or inactivated

Question 20

Absolute refractory phase

Answer 20

A brief period of complete insensitivity to stimuli

Question 21

Relative refractory phase

Answer 21

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

Question 22

How are action potentials created?

Answer 22

A stimulus that depolarizes a neuron to -40 mV will cause it to spike so that the cell becomes temporarily positive, causing voltage-gated Na+ channels to open and letting Na+ ions in. This causes an action potential, and the depolarization of the cell will cause the ones next to it to depolarize as well, moving the action potential along the neuron.

Question 23

Conduction velocity

Answer 23

The speed at which an action potential is propagated along the length of an axon

Question 24

Saltatory conduction

Answer 24

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

Question 25

Multiple sclerosis (MS)

Answer 25

A disorder characterized by the widespread degeneration of myelin

Question 26

Postsynaptic potential

Answer 26

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

Question 27

Excitatory postsynaptic potential (EPSP)

Answer 27

A depolarizing potential in a neuron that is normally caused by synaptic excitation. EPSPs increase the probability that the postsynaptic neuron will fire an action potential

Question 28

Inhibitory postsynaptic potential (IPSP)

Answer 28

A hyperpolarizing potential in a neuron. IPSPs decrease the probability that the postsynaptic neuron will fire an action potential

Question 29

Spatial summation

Answer 29

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

Question 30

Temporal summation

Answer 30

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

Question 31

How is the resting potential maintained?

Answer 31

Diffusion Electrostatic pressure

Question 32

How do the ions move in an action potential?

Answer 32

When the threshold is reached, the voltage-gated channels open, allowing sodium ions in and causing depolarization. They become inactive at the peak, and the outflow of potassium ions cause hyperpolarization

Question 33

What causes the electric potential in a neuron to reach the threshold?

Answer 33

Signals received from presynaptic neurons