CBNS 120 Midterm 1

Cajal used the [_________] stain to prove the [___________] Doctrine.

golgi; neuron

Conductance is the reciprocal of:

resistance

Hyperpolarization occurs when the membrane potential becomes more [_____________], while depolarization causes the membrane potential to become more [_______________].

negative; positive

Permeability indicates the presence of ______, while conductance requires _______ and ______.

open channels; ions; permeability

Permeability is the ability of the membrane to conduct _________ .

ions

Categories of ion channels include ________, _________, and _________.

stretch-activated; voltage-activated; ligand-activated

Conductance can be distinguished from permeability by the requirement for ___________.

charge

The membrane potential at which the diffusional force created by an ion gradient is equal and opposite to the electrical force is called the [________________].

equilibrium potential

The difference between the membrane potential (Vm) and the equilibrium potential (Ex) for any given ion is called [_____________].

driving force

When current flow across the membrane in one direction exceeds current flow in the opposite direction, it is called ___________.

rectification

Ion channels flux (transfer) ions across the membrane at rates of

a.) 10^7-10^8 ions/sec

b.) 10^3-10^5 ions/sec

c.) 10^2-10^3 ions/sec

d.) 10^9-10^10 ions/sec

10^7-10^8 ions/sec

Driving Force is:

a.) equals the difference between the equilibrium potential (Ex) and the membrane potential (Vm).

b.) zero when the Vm = Ex

c.) is required for current to flow across the membrane

d.) All of the above

d.) all of the above

Ion channel activity is:

a.) Random

b.) Stochastic

c.) Probablistic

d.) All of the above

d.) all of the above

In voltage-gated channels, the S4 transmembrane segment functions as a _______ and the region between S5 and S6 functions as the ________.

voltage sensor; pore

Regions of channel proteins that cross the membrane from one side (extracellular) to the other (cytoplasmic) are called:

A.) membrane-spanning

B.) transmembrane segments

C.) extracellular loops

D.) All of the above

E.) A and B only

E.) A and B only

Match the questions and answers.

- Na/K ATPase

- Na/Ca Exchanger

- Ca ATPase

- NaKCC1

a.) Symporter

b.) electrogenic

c.) antiporter

d.) primary transporter

b;c;d;a

Primary Transporters/Pumps transport ions at rates of:

A. 10^0-10^3 ions/sec

B. 10^2-10^4 ions/sec

C. 10^7-10^8 ions/sec

D. (A) and (C)

A. 10^0-10^3 ions/sec

The following are specific blockers of the Na/K Pump: (Choose all that are correct)

a.) tetrodotoxin

b.) ouabain

c.) alpha-bungarotoxin

d.) digoxin

b; d

Injection of Na ions into a neuron would: (check all possible answers)

a.) Hyperpolarize the membrane potential

b.) Activate the Na/K pump

c.) Activate the Na/Ca exchanger

d.) Cause a current to flow

a; b; d

Secondary transporters move ions across the membrane at rates of:

A. 10^0-10^3 ions/sec

B. 10^2-10^4 ions/sec

C. 10^7-10^8 ions/sec

D. (A) and (C)

B. 10^2-10^4 ions/sec

Imagine you are doing experiments with Hodgkin and Huxley on the squid giant axon. What would be the effect(s) of decreasing extracellular Na concentration? (check all possible answers)

a.) Depolarize the cell

b.) Hyperpolarize the cell

c.) Reduce the amplitude of the action potential

d.) Increase intracellular Ca concentration

b; c; d

The falling phase of the action potential is caused by:

A. Na influx

B. K efflux

C. Na channel inactivation

D. All of the above

E. (B) and (C) only

E. (B) and (C) only

The transporter that sequesters Ca in the endoplasmic reticulum is:

a.) The plasma membrane Ca ATPase

b.) The Na/Ca exchanger

c.) The SERCA pump

d.) KCC1

c.) The SERCA pump

A complete cycle of the Na/K ATPase requires:

A.Na binding

B. K binding

C. Phosphorylation

D. Dephosphorylation

E. All of the above

F. A, B, and C only

E. All of the above

Secondary transporters derive their energy from:

A. ATP

B. Ion gradients

C. GTP

D. All of the above

E. (B) and (C) only

B. Ion gradients

Predict the resting potential (Em) for a neuron, where [K]i = 95 mM, [K]o = 5 mM, [Na]in= 15 mM, [Na]o= 140 mM, at room temperature (T=298oK), with R=8.3 coul-volts/deg-mol, F = 96,500 coul/mol. Assume that the Na permeability of the cell membrane is 1/50 that of the K permeability, that the neuron has been exposed to ouabain, and that chloride ions are in equilibrium and hence do not contribute to Em.

A. -58 mV

B. -64 mV

C. -67 mV

D. -75 mV

B. -64 mV

Refer to the previous scenario (Question 11). What happens to Em when ouabain is removed? Explain why and predict the new value for Em.

A. -58 mV

B. -64 mV

C. -67 mV

D. -75 mV

C. -67 mV

Assuming EK is more negative than Em, an increase in leak gK would (choose all that apply):

a.) depolarize the membrane

b.) hyperpolarize the membrane

c.) cause increased excitation

d.) cause decreased excitation

b;d

The slow AHP (after-hyperpolarization lasting for seconds) results from:

A. The Na/K ATPase

B. delayed rectifier gK

C. Calcium-activated gK

D. all of the above

E. A and C only

C. Calcium-activated gK

In the Hodgkin-Huxley squid axon experiments, the late outward current could be isolated by:

a.) Treating the axon with TEA (tetraethylammonium)

b.) treating the axon with TTX (tetrodotoxin)

c.) Stepping the membrane potential to the Na equilibrium potential

d.) all of the above

e.) B and C only

e.) B and C only

At threshold for the action potential:

A.) Inward Na current is equal to the outward delayed rectifier K current

B.) The outward leak K current equals the inward Na current

C.) Inward K current is equal to the outward Na current

D.) Inward K current is equal to inward Na current

B.) The outward leak K current equals the inward Na current

Hodgkin and Huxley theorized movement of 4 "n" gating particles from position "n-1" to "n" to describe:

A.) Na current activation

B.) K current activation

C.) Na current inactivation

D.) K current inactivation

B.) K current activation

In Hodgkin-Huxley's mathematical, the "h" particle corresponds to:

a.) The Na channel voltage sensor

b.) The K channel voltage sensor

c.) The Na channel inactivation particle

d.) None of the above

c.) The Na channel inactivation particle

Steady state inactivation can be decreased by:

A.) Depolarizing conditioning voltage steps

B.) Hyperpolarizing conditioning voltage steps

C.) No conditioning voltage steps

D.) none of the above

B.) Hyperpolarizing conditioning voltage steps

Na current during the action potential decreases due to:

a.) decreased driving force

b.) increased driving force

c.) inactivation

d.) All of the above

e.) A and C only

e.) A and C only

In the squid axon experiments, the early inward current can be isolated by:

a.) Treatment with TTX

b.) Treatment with alpha-bungarotoxin

c.) Treatment with TEA

d.) Stepping to the Na equilibrium potential

c.) Treatment with TEA

At membrane potentials positive to ENa,

A.) Na moves inward

B.) Na moves outward

C.) K moves outward

D.) B and C

D.) B and C

Spike frequency adaptation can be reduced by:

a.) Blocking gCl

b.) Blocking gNa

c.) Blocking gKCa

d.) Activating gKCa

c.) Blocking gKCa

Gating current indicates:

A.) Increased capacitive current

B.) Movement of the voltage sensor

C.) Movement of the inactivation particle

D.) Movement of the IFM particle

B.) Movement of the voltage sensor

Refractory period results from:

A.) Na channel activation

B.) Na channel inactivation

C.) K channel activation

D.) All of the above

E.) B and C only

E.) B and C only

Increasing the length of the "chain" in Shaker K channels:

A.) Abolishes inactivation

B.) Accelerates inactivation

C.) Slows inactivation

D.) Enhances activation

C.) Slows inactivation

Gating modifier toxins:

A.) Block the channel pore

B.) Increase voltage sensitivity of channels

C.) Decrease voltage sensitivity of channels

D.) All of the above

E.) B and C

E.) B and C

Myocardial cells have long duration action potentials because of:

a.) gNa

b.) gK

c.) gCa

d.) gCl

c.) gCa

Currents in the Hodgkin-Huxley equations include:

a.) IK

b.) INa

c.) IC

d.) All of the above

e.) A and B only

d.) All of the above

During the relative refractory period:

A.) Action potentials occur spontaneously

B.) Action potential initiation can be accomplished by imposing a stronger stimulus

C.) Threshold is elevated

D.) All of the above

E.) B and C only

E.) B and C only

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