Lecture 11 & 12

Question 1

Ions move in the direction opposite to that favored by the chemical concentration gradient when _____.

a. simple diffusion operates after active transport has been permanently halted by being poisoned
b. sodium ions enter a neuron during the depolarization phase of an action potential
c. potassium ions exit the neuron during the repolarization phase of an action potential
d. they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them
e. proteins leak out of a neuron

Answer 1

d. they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them

Question 2

Two fundamental concepts about the ion channels of a “resting” neuron are that the channels _____.

a. open in response to stimuli, and then close simultaneously, in unison
b. are always closed, but ions move closer to the channels during excitation
c. open and close depending on stimuli, and are specific as to which ion can traverse them
d. are always open, but the concentration gradients of ions frequently change

Answer 2

c. open and close depending on stimuli, and are specific as to which ion can traverse them

Question 3

The concentrations of ions are very different inside and outside a nerve cell due to _____.

a. symports and antiports
b. sodium-potassium pumps
c. diffusion
d. osmosis

Answer 3

b. sodium-potassium pumps

Question 4

*LOOK AT QUESTION 4*
The membrane potential is closest to the equilibrium potential for potassium at label \_\_\_\_\_.
a. A 
b. B 
c. C 
d. D

Answer 4

d. D

Question 5

In a neuron, during the depolarization phase that may trigger an action potential _____.

a. most voltage-gated sodium channels become inactivated
b. most voltage-gated sodium channels are open
c. most voltage-gated sodium and potassium channels are open
d. some voltage-gated sodium channels are open
e. most voltage-gated potassium channels are open

Answer 5

d. some voltage-gated sodium channels are open

Question 6

Which of the following statements about action potentials is correct?

a. Action potentials for a given neuron vary in duration.
b. Action potentials for a given neuron vary in magnitude.
c. Movement of ions during the action potential occurs mostly through the sodium pump.
d. Action potentials are propagated down the length of the axon.

Answer 6

d. Action potentials are propagated down the length of the axon.