Map #5 - Neurophysiology I And Ii: Membrane Potentials And Action Potentials

Front 1

What is the approximate resting membrane potential of neurons?

Back 1

-70mV

Front 2

Which of the following best describes the electrochemical forces acting on sodium and potassium ions at the resting membrane potential?
a. The force on sodium ions is to move out of the cell, and the force on potassium is to move into the cell.
b. The force on sodium ions is to move into the cell, and the foce of potassium is to move out of the cell.
c. There is no force on either ion to move.
d. Forces on both sodium and potassium ions are to move out of the cell.
e. Forces on both sodium and potassium are to move into the cell.

Back 2

b. The force on sodium ions is to move into the cell, and the force on potassium ions is to move out of the cell.

Front 3

At the resting membrane potential, the membrane is most permeable to ________, which moves ________ the cell due to its electrochemical gradient.

Back 3

potassium : out of

Front 4

If, under resting conditions, the membrane is much more permeable to sodium than potassium, what would happen to the resting membrane potential?

Back 4

approach sodium's equilibrium potential

Front 5

If we apply an electrical stimulus to a muscle cell to cause it to contract, the magnitude of that stimulus must be strong enough to reach a critical value that is essential in initiating the process of contraction. This critical value is known as __________.

Back 5

threshold

Front 6

Which of the following represents a state of depolarization of a neuron?

Back 6

-70 mV to +30 mV

Front 7

A change in a cell's membrane potential, such that it becomes more negative, is referred to as a ________.

Back 7

hyperpolarization

Front 8

A ________ is a subthreshold change in membrane potential within the cell body that decays as it travels away from its point of origin.

Back 8

graded potential

Front 9

If the graded potential remains above threshold once it reaches the ________, an action potential will be generated.

Back 9

axon hillock

Front 10

The opening of sodium channels causes a rapid ________ of sodium that ________ the neuron's membrane.

Back 10

influx : depolarizes

Front 11

The repolarization phase of the action potential in a neuron is driven by the ________.

Back 11

closure of sodium channels and opening of potassium channels

Front 12

For the sodium channel to open and allow sodium into the cell, ________.

Back 12

the activation and inactivation gates must both be open

Front 13

The jumping of an action potential from node-to-node is called ________.

Back 13

saltatory conduction

Front 14

Under resting conditions, the sodium channel responsible for generating an action potential is closed and incapable of opening.

Back 14

False

Front 15

Where do most action potentials originate?

Back 15

initial segment

Front 16

What opens first in response to a threshold stimulus?

Back 16

Voltage-gated Na+ channels

Front 17

What characterizes depolarization, the first phase of the action potential?

Back 17

The membrane potential changes from a negative value to a positive value.

Front 18

What characterizes repolarization, the second phase of the action potential?

Back 18

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

Front 19

What event triggers the generation of an action potential?

Back 19

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

Front 20

What is the first change to occur in response to a threshold stimulus?

Back 20

Voltage-gated Na+ channels change shape, and their activation gates open.

Front 21

What type of conduction takes place in unmyelinated axons?

Back 21

continuous conduction

Front 22

An action potential is self-regenerating because __________.

Back 22

depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment

Front 23

Why does regeneration of the action potential occur in one direction, rather than in two directions?

Back 23

The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.

Front 24

What is the function of the myelin sheath?

Back 24

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

Front 25

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

Back 25

Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.

Front 26

In which type of axon will velocity of action potential conduction be the fastest?

Back 26

Myelinated axons with the largest diameter

Front 27

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

Back 27

resting membrane potentail

Front 28

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

Back 28

leak channels

Front 29

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

Back 29

The inside surface of the plasma is much more negatively charged than the outside surface.

Front 30

The plasma membrane is much more permeable to K+ than to Na+. Why?

Back 30

There are many more K+ leak channels than Na+ leak channels in the plasma membrane.

Front 31

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.

Back 31

The presence of concentration gradients and leak channels

Front 32

What prevents the Na+ and K+ gradients from dissipating?

Back 32

Na+-K+ ATPase

Front 33

Which ion(s) is/are higher in concentration inside the cell compared to outside?

Back 33

potassium

Front 34

Voltage-regulated channels are located

Back 34

in the membrane of axons

Front 35

Action potentials occur in the membrane of

Back 35

axons