Practice quiz 2

Question 6

1 / 1 pts

Which of the following is TRUE regarding membrane hyperpolarization? 

  

Interior of cell becomes more positive

 

  

May result from potassium ion efflux (leaving the cell)

 

  

Chloride ions rushes out of the neuron

 

  

Cell becomes less polarized than at rest

 

1 / 1 pts

Question 5

What happens to the membrane potential of a cell that gets poisoned ouabain?

Ouabain is a drug that blocks Na+/K+ pumps.

  

Membrane potential stays the same as the RMP

 

  

Depolarized

 

  

Hyperpolarized

 

Question 4

1 / 1 pts

What happens to the membrane potential of a cell that has more chloride ions (Cl-) entering it?

 

  

Membrane potential stays the same as the RMP

 

  

Depolarized

 

  

Hyperpolarized

 

Question 3

1 / 1 pts

The resting potential of a neuron is less negative (at –70 mV) than that of skeletal muscle fiber (which is at –90 mV, as you may remember from BIOL 40A).

 

Without doing any research and based only on what you have learned so far, which of the following explanations is most likely true?

  

Skeletal muscle fibers have more Na+ leak channels than neurons, so they lose more positive charges.

 

  

Skeletal muscle fibers have more Cl– leak channels than neurons, so they lose more negative charges

 

  

Skeletal muscle fibers have more Na+/K+ ATPases than neurons, so they lose more positive charges

 

  

Skeletal muscle fibers have more K+ leak channels than neurons, so they lose more positive charges

 

 

Question 2

1 / 1 pts

What is the Na+/K+ ATPase?

Choose all the correct answers

  

A sodium-potassium ion pump, one of the most important ATP-consuming pumps that move ions against their electrochemical gradients.

 

  

A transmembrane protein that moves three Na+ ions out and two K+ ions into the cell, per each time it runs (pumps).

 

  

A molecular machine that maintains/creates a high concentration of Na+ in the extracellular fluid and a lower concentration in the cytosol.

 

  

A transmembrane protein that moves two Na+ ions out and three K+ ions into the cell, per each molecule of ATP hydrolyzed.

 

  

A molecular machine that maintains/creates a high concentration of K+ in the cytosol and a lower concentration in the extracellular fluid.

 

Question 1

1 / 1 pts

Think about how the cell establishes the RMP:

What keeps Na+ and K+ ions from eventually balancing out their concentrations across the neuron membrane and eliminating their electrochemical gradients, as they slowly spill through their respective leak channels? 

  

Protein pumps that consume the energy stored in ATP to push Na+ and K+ ions against their electrochemical gradients

 

  

Protein channels that allow Na+ and K+ ions to flow along their electrochemical gradients

 

  

Neurons continuously synthesize K+ and destroy Na+ ions, so K+ and Na+ accumulate on opposite sides of the plasma membrane because ions cannot freely pass through the lipid bilayer.

 

  

Each type of leak channel only allows one type of ions to pass through, so they force Na+ and K+ to move depending on the direction in which the leak channels face across the plasma membrane.

 

Question 8

1 / 1 pts

What is the approximate amplitude of the IPSP (how many mV)?

  

-10mV

 

  

+10mV

 

  

+60mV

 

  

-60mV

 

 

Question 7

1 / 1 pts

What happens to the membrane potential of cell that becomes less permeable to K+?
In other words, K+ is retained in the cell as opposed to leaking out.

  

depolarized

 

  

hyperpolarized

 

  

Membrane potential stays the same as the RMP

 

 

Question 9

1 / 1 pts

What is the approximate amplitude of the EPSP (how many mV)?

  

-10mV

 

  

+10mV

 

  

+60mV

 

  

-60mV

 

Question 10

1 / 1 pts

How would these graded potentials be summed together?

  

Spatial summation

 

  

EPSP-IPSP cancellation

 

  

Temporal summation

 Question 11

1 / 1 pts

If the IPSP had not occurred, would the EPSP be able to trigger an action potential?

 

  

Yes

 

  

No

 

Question 12

1 / 1 pts

Which of the following is NOT related to the opening of sodium ion channels?

  

Sodium rushes into the neuron

 

  

Cell becomes less polarized

 

  

Cell depolarizes

 

  

Interior of cell becomes more negative

 

Question 14

1 / 1 pts

During an action potential, repolarization is caused by:

  

Na+ entering the axon c

 

  

K+ entering the axon

 

  

Na+ exiting the axon

 

  

K+ exiting the axon

 

Question 13

1 / 1 pts

The channels that open at the threshold potential of –55 mV to cause depolarization are:

  

voltage-gated Na+ channels.

 

  

voltage-gated K+ channels.

 

  

Na+ leak channels

 

  

ligand-gated K+ channels.

 

Question 15

1 / 1 pts

Which of the following is NOT related to the opening of potassium ion channels?

  

Potassium rushes into the neuron

 

  

Cell becomes more polarized

 

  

Cell repolarizes

 

  

Interior of cell becomes more negative

 

Question 16

1 / 1 pts

Match the phases of the action potential with the correct number to organize them in the correct sequence.

First

 

               depolarization             

Second

 

               repolarization             

Third

 

               hyperpolarization             

Question 17

1 / 1 pts

The membrane potential at which sodium ion channels CLOSE and potassium channels OPEN during an action potential is

  

−90 mV

 

  

−70 mV

 

  

−55 mV

 

  

+30 mV

 

 

18.During the absolute refractory period, the axon membrane:

  

is more responsive to depolarization.

 

  

is unable to generate an action potential.

 

  

is at –90 mV.

 

  

contains open voltage-gated Na+ channels.

 

19.Action potential propagation always occurs:

  

from axon hillock to axon terminal.

 

  

from axon terminal to axon hillock.

 

  

from dendrites to axon hillock.

 

  

from axon hillock to dendrites.

 

20. The threshold potential is best defined as the potential at which...

  

Voltage-gated potassium channels open

 

  

Chemically gated sodium channels open

 

  

Voltage-gated sodium channels open

 

  

Voltage-gated potassium channels close