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Neuroanatomy and neurophysiology > Neuron excitation > Flashcards

Neuron excitation Flashcards

1
Q

The ability of an ion to bring the membrane potential towards its equilibrium potential based on the Nernst Equation is greater if the

A. equilibrium potential of the ion is nearer the actual membrane potential
B. concentration gradient of the ion across the membrane is greater
C. electrical gradient of the ion across the membrane is greater
D. permeability of the membrane to the ion is greater

A

D

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2
Q

The resting membrane potential is due mainly to the movement of potassium ions across the membrane because:

A. the concentration and electrical gradient of the Na+K+ATPase pump for the 3 of Na+ ions out of the cell
B. only 2 K+ ions are pumped in by the Na+K+-ATPase pump for 3 of Na+ions out of the cells
C. during resting conditions, K+ is in equilibrium
D. K+ has the largest resting conductance

A

D

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3
Q

Which of the following effects of the action of Na+-K+-ATPase pump contributes the most to the generation of the resting membrane potential?

A. Maintenance of electrochemical gradient of Na+ ions and K+ ions across the membrane
B. Asymmetric distribution of diffusable permeant ions in the presence of a non-diffusable ion
C. electrogenic effect of pumping 3 Na ions out of the membrane and 2 K+ ions into the cell
D. Hydrolysis of ATP to ADP to produce conformational change of the Na+K_ ATPase pump

A

A

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4
Q

There is a high density of voltage gated sodium channels in all of the following except:

A. internodal segments of the axon
B. Initial segment of the axon
C. Nodes of Ranvier
D. Axon hillock

A

A

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5
Q

The resting membrane potential differs from the equilibirium potential of potassium because:

A. the Na+K+AtPase pump counteracts passive fluxes of sodium and potassium ions
B. The ratio of open potassium leak channels to sodium channels is very high
C. The large non-diffiuable anions are present in the interior of the cell.
D. The membrane is permeable to ions other than potassium

A

D

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6
Q

Summation may occur in all of the following except:

a. Electrotonic potential
b. Generator potential
c. Synaptic potential
d. Action potential

A

D

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7
Q

The neuronal membrane potential would be nearer the threshold level for generating an ActionPotential if the

a. voltage gated K+ channels were increased
b. membrane were to possess only K+ channels
c. number of open Cl- channells were increased
d. membrane permeability for Na+ channels were opened

A

D

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8
Q

All of the following contribute to the downward slope of the spike potential of an action potential EXCEPT:

a. voltage-gated potassium channels
b. voltage-gated sodium channels
c. potassium leak channels
d. Na+-K+-ATPase pump

A

B

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9
Q

An action potential can be produced with the least stimulation during (the):

a. Downward slope of the spike potential
b. Upward slope of the spike potential
c. After-hyperpolarization
d. After-depolarization

A

D

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10
Q

Which of the following is/are TRUE of saltatory conduction?

a. It consists of action potentials ‘jumping’ from one internode to another
b. It proceeds only in an orthodromic direction
c. It occurs because of current sink
d. all of the above are true.

A

C

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11
Q

In which of the following components of the action potential is conductance through voltage-gated potassium channels NOT contributory to the decreased membrane excitability?

a. Upward spike of spike potential
b. Relative refractory period
c. After-hyperpolarization
d. All of the above

A

A

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12
Q

44.which of the following is/are TRUE of voltage-gated potassium channels?

a. They open when threshold potential for the generation of the action potential is reached.
b. Their slow return to the closed state leads to after-
hyperpolarization
c. They display a high conductance in the resting membrane
d. all of the above

A

B

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13
Q

All of the following are TRUE of voltage-gated sodium ion channels EXCEPT:

a. They assume a closed inactivatable state before the membrane reaches the equilibrium potential for Sodium
b. closure of their inactivation gate causes absolute refractory period
c. They are opened when the membrane is hyperpolarized
d. They are virtually closed when the cell is at rest

A

C

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14
Q

A rapid, all-or-none change in the membrane potential followed by a return to the resting membrane potential

A

Action potential

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15
Q

The difference between the charges on the opposite sides of a cell membrane when the cell is at rest

A

Resting membrane potential

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16
Q

The resting membrane potential

A

-70mV

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17
Q

The change in membrane potential from -70mV to -60mV

A

Depolarization

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18
Q

The change in membrane potential from -70mV to -80mV

A

Hyperpolarization

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19
Q

The membrane voltage at which there is a 50:50 chance of generating an action potential

A

Threshold membrane potential

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20
Q

Ions that generate action potential

A

Na+, K+

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21
Q

Transient depolarization of the post-synaptic membrane potential

A

Excitatory Post-synaptic Potential (EPSP)

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22
Q

Transient hyperpolarization of the post-synaptic membrane potential

A

Inhibitory Post-synaptic Potential (IPSP)

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23
Q

Which causes EPSP?

A

Entrance of Na+ to cell

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24
Q

What causes IPSP?

A

Exit of K+

Entrance of Cl-

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25
Q

Types of summation

A

Spatial summation,

Temporal summation

26
Q

What is the ionic basis that begins the generation of an action potential?

A

The influx of Na+ into the cell caused by the opening of Na+ voltage-gated channels. This results in the depolarization of the membrane

27
Q

The falling phase of the action potential is the result of which processes?

A

The reduction in Na+ influx and increase in K+ flow out of the cell

28
Q

Two gates of Na+ voltage-gated channels

A

A voltage-gate and an inactivation gate

29
Q

Voltage-gated K+ channels have two gates like Na+ voltage-gated channels. T/F

A

F

They only have one gate

30
Q

What causes the closing of K+ voltage-gated channels when the action potential is hyperpolarized?

A

The return of the negative membrane potential

31
Q

What causes the closing of Na+ voltage-gated channels at the peak of depolarization?

A

The inactivation gate

32
Q

What does it mean when a cell is refractory?

A

It is unresponsive to further stimulation. it cannot fire a second action potential no matter how strongly it is stimulated

33
Q

The period/state where a cell is unresponsive to stimulation and cannot fire a second action potential

A

Absolute refractory period

34
Q

Why does a cell undego absolute refractory period?

A

Because a large fraction of its Na+ channels are voltage inactivated and cannot be reopened until the membrane is repolarized.

35
Q

What is relative refractory period?

A

The period in the latter part of the action potential when the cell is able to fire a second action potential through a stronger than normal stimulus.

36
Q

In the nervous system, where is the action potential generated?

A

Axon hillock

37
Q

Why is the action potential generated in the axon hillock in the nervous system?

A

The axon hillock contains a high density of Na+ voltage-gated channels, giving it the lowest threshold in the neuron

38
Q

Na+ channels that generate the action potential are concentrated at the nodes of Ranvier. T/F

A

T

39
Q

The process of “jumping” of action potential from one node of Ranvier to another

A

Saltatory conduction

40
Q

Why don’t the action potential of myelinated axons not have a hyperpolarizing afterpotential or extended relative refractory period?

A

They do not have K+ channels at their nodes

41
Q

Which of the ff. Processes contributes the most to the generation of the resting membrane potential?

A. Gibbs-donan equilibrium
B. Electrogenic effect of na-k atpase pump
C. Ionic diffusion of permeant ions through leak
channels - ans
D. Movement of potassium ions through voltage-gated potassium channels

A

C

42
Q

Which of the following is/are features of voltage-
gated sodium channel/s

a) They are open when the membrane is hyperpolarized
b) They have high conductance in the resting state
c) They are closed when the cell is at rest
d) They pump 3 sodium out of the cell and 2 potassium ions inwards

A

C

43
Q

Graded potentials: action potential or local potential?

A

Local potential

Action potentials are all or none.

44
Q

At RMP, what is the equilibrium potential of sodium (mV)?

A

+60

45
Q

At RMP, what is the equilibrium potential of K (mV)?

A

-90

46
Q

At RMP, what is the equilibrium potential of Cl (mV)?

A

-70

47
Q

Accounts for Absolute Refractory Period

A. open voltage-gated Na channels
B. Closure of activation gate of voltage gated Na channels
C. Efflux of K via leak channels
D. All of the above

A

B

48
Q

What is the effect of myelin sheaths on action potential transmission?

A. Increased conductance
B. decreased space constant
C. Increased time constant
D. all of the above

A

A

49
Q

At resting membrane potential, which of the following statements about the voltage-gated sodium ion (Na+) channels is TRUE?

A) activation gates are closed and inactivation gates are open
B) activation gates are open and inactivation gates are closed
C) activation and inactivation gates are open
D) activation and inactivation gates are closed
E) activation and inactivation gates alternate between open and closed

A

A

50
Q

During depolarization, which of the following statements about voltage-gated ion channels is TRUE?

A) K+ gates open before Na+ gates
B) Na+ gates open before K+ gates
C) Na+ and K+ gates open at the same time
D) Na+ gates open while K+ gates remain closed
E) K+ gates open while Na+ gates remain closed

A

D

51
Q

Depolarization occurs because

A) more K+ diffuse into the cell than Na+ diffuse out of it.
B) more K+ diffuse out of the cell than Na+ diffuse into it.
C) more Na+ diffuse into the cell than K+ diffuse out of it.
D) more Na+ diffuse out of the cell than K+ diffuse into it.
E) both Na+ and K+ diffuse into the cell.

A

C

52
Q

The sodium-potassium pump is involved in establishing the resting membrane potential. T/F

A

T

53
Q

The voltage-gated potassium channels close before the membrane potential is brought back to its resting level. T/F

A

F

54
Q

Depolarization occurs because…

A) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close.

B) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value.

C) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.

D) more sodium ions diffuse into the cell than potassium ions diffuse out of it.

E) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases.

A

D

55
Q

Repolarization occurs because…

A) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close.

B) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value.

C) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.

D) more sodium ions diffuse into the cell than potassium ions diffuse out of it.

E) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases.

A

A

56
Q

Hyperpolarization, or afterpotential occurs because…

A) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close.

B) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value.

C) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.

D) more sodium ions diffuse into the cell than potassium ions diffuse out of it.

E) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases.

A

C

57
Q

After the passage of the action potential, the sodium-potassium pump reestablishes the resting membrane potential. T/F

A

T

58
Q

The sodium-potassium pump uses bulk transport to move the sodium and potassium ions. T/F

A

F

59
Q

An action potential

A) prevents the neuron cell membrane from altering its charge.

B) causes the inside of the neuron cell membrane to become positive and the outside negative.

C) causes the inside of the neuron cell membrane to become positive and the outside neutral.

D) causes the outside of the neuron cell membrane to become positive and the inside negative.

E) causes the outside of the neuron cell membrane to become positive and the inside neutral.

A

B

60
Q

An action potential generates local currents that tend to ________ the membrane immediately adjacent to the action potential.

A)	depolarize
B)	repolarize
C)	hyperpolarize
D)	stabilize
E)	neutralize
A

A

61
Q

The absolute refractory period is the period of time during which

A) a second action potential cannot be generated.
B) a second action potential is generated.
C) the action potential ceases.
D) the action potential decreases in magnitude.
E) the action potential changes direction.

A

A

62
Q

Threshold is the minimum current required for the cell membrane to generate an action potential. T/F

A

T

Neuroanatomy and neurophysiology (16 decks)

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