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KN 251 > Membrane Potential and Excitation > Flashcards

Membrane Potential and Excitation Flashcards

1
Q

Separation of positive and negative charges is what type of energy?

A

Potential

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2
Q

Energy that allows separated charges to move freely. This flow is called current, amps.

A

Kinetic Energy

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3
Q

The force which slows down current flow.

A

Resistance

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4
Q

A substance which inhibits current flow

A

Insulator

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5
Q

A substance which promotes current flow

A

Conductor

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6
Q

Current = ?

A

V/R

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7
Q

Why does current flow occur in living systems?

A

Ions flow!

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8
Q

Where do they flow across? (What is the insulator of charge separation?)

A

Membrane - separates charges

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9
Q

The integral, transmembrane proteins which serve as conductors in living systems that allow ions to flow when open

A

Channels

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10
Q

Leakage channels that are typically always open that allow ions to flow through them

A

Passive Channels

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11
Q

Gated channels that only open when stimulated

A

Active Channels

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12
Q

Type of gated channel that is opened by a chemical . Opens when chemical binds to transmembrane protein/receptor to provide pathway for ions to flow inside or outside membrane

A

Chemically gated channel

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13
Q

Type of active channel that is opened by a change in potential energy, there is a change in the voltage distribution across membrane due to ions, which opens channel to allow ions to flow across membrane

A

Voltage Gated Channel

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14
Q

Current flow depends on two factors. What are they?

A

Electrical Charge Movement

Chemical Diffusion

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15
Q

Current flow factor where ions that are charged will move toward an area that contains an opposite charge

A

Electrical Charge Movement

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16
Q

Current flow factor where chemicals diffuse from an area of high concentration to low concentration

A

Chemical Diffusion

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17
Q

Together, electrical charge movement and chemical diffusion are known as…

A

Electrochemical Gradient

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18
Q

Flow of ions across membranes is controlled by this, which conducts the current and carries the kinetic energy used to do the work of the action potential

A

Electrochemical Gradient

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19
Q

It is created by unequal concentrations of ions of both charges that exist in a narrow band around each side (cytoplasmic and extracellular) of the plasma membrane.

A

Resting Membrane Potential

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20
Q

Potential energy is created due to the chemical and electrical forces that develop across the membrane

Different ions, different concentrations of each ion, different charges on ions

A

Resting Membrane Potential

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21
Q

Charged separation is referred to as _________, it is the basis of all electrical conductivity of cells capable of conducting action potential

A

Polarization of the membrane

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22
Q

What are the units of charge separation?

What is the orientation (outside with respect to inside or inside with respect to outside?)

A

millivolts

Inside with respect to outside

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23
Q

What is typical cell membrane charge, or the resting membrane potential?

A

-70mV

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24
Q

Note: cell as whole is neutral, but separation of charges occurs where?

A

At the membrane

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25
Q

Specific ions separate themselves at different concentrations immediately around the membrane, creating (generation and maintenance of RMP)

A

Polarization

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26
Q

Na, K, Cl are capable or incapable of moving outside/inside the membrane?

Negatively charged proteins are fixed/capable of moving?

A

Capable

Fixed. Only positively charged ions can move.

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27
Q

Gnereates concentration difference for Na+ and K+, require ATP and translocate ions against concentration gradient

A

ATPase pump

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28
Q

How much NA and K are pumped in or out simultaneously of an ATPase pump?

A

3Na+ pumped out

2K pumped in

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29
Q

What type of port is the ATPase? How many ions are moving?

A

antiport, 5

30
Q

There are many pumps in the plasma membrane which pump all the time

A

!

31
Q

Pumping prevents what from being reached?

A

Equilibrium

32
Q

How does it prevent equilibrium?

A

Prevents equilibrium from being reached to reach electrochemical gradient

33
Q

Are there more or less K and Na passive channels in the plasma membrane?

How else is it maintained?

A

K channel>Na channel

K can move more freely out of the membrane

34
Q

Why does K move outside the cell?

A

Because it is clumped inside the cell, tends to want to move out

35
Q

Why does Na want to move in?

A

Because it is clumped outside cell, but can’t come in as easily as K can move out

36
Q

Why doesn’t K (positively charged) want to stay in the more negatively charged cell?

A

Because of the force of the concentration gradient

37
Q

While most cells maintain the resting membrane potential throughout their lifetime, certain cells change it - like nerve and muscle cells. What do they have?

A

Gated Channels

38
Q

These can be chemical or voltage, and open and close in response to stimuli. They allow ions to flow across a membrane

A

Gated Channels

39
Q

Cells which remain at rest have small or large amounts of ions moving back and forth?

A

Small, RMP stays the same.

40
Q

Cells that cannot alter potential do not have

A

Gated Channels

41
Q

A cell where charge is separated across a membrane, like RMR

A

Polarized Cell

42
Q

Not polarized cell, charges have been allowed to follow. Potential energy = 0

A

Depolarized Cell

43
Q

A cell that is more polarized than resting potential. Potential energy is greater

A

Hyperpolarized Cell

44
Q

A cell whose polarity has returned to baseline. It could return from being hyperpolarized or depolarized

A

Repolarized Cell

45
Q

Returning from hyperpolarized = increase or decrease in potential energy?
Returning from depolarized = increase of decrease in potential energy?

A

Decrease

Increase

46
Q

Two types of mechanisms of change in plasma membrane potential

A

Graded Potential

Action Potential

47
Q

These events involve movement of ions across the plasma membrane in opposite directions to change potential energy into kinetic energy across the membrane

A

Graded Potential and Action Potential

48
Q

Both graded and action potential involve movement of ions across the plasma membrane in opposite directions to change the potential energy across the membrane. How do they differ?

A

The amount of ions that move and the type of membrane channel which opens

49
Q

A few ions cross the membrane, chemically gated, still enough to change potential energy, gives you what?
-Note: limited to small section of the membrane

A

Graded potential

50
Q

Voltage gated channels, many ions crossing the membrane, results in a large potential
Note: not limited to small section, travels entire length of the cell

A

Action potential

51
Q

What type of channels exist in cells capable of conducting graded potentials?

A

Graded potentials

52
Q

Is the area that changes potential large or small in graded potentials?

Do many or a few ions move across the membranes?

A

small

A few

53
Q

Can graded potentials depolarize and/or hyperpolarize? What determines this?

A

Both. It is determined by which ions are moving across the membrane (which chemically gated channels)

54
Q

When a cell is depolarized, do ions move in or out of the cell?

What about hyperpolarization?

A

Ions move in when depolarized (+ charges neutralize negative charge of cell)

Ions move out when polarized

55
Q

What type of channels do cells capable of performing action potentials contain in their plasma membranes?

A

Voltage-gated channels.

56
Q

Voltage gated channels in action potentials are specific for a single ion. Cells with voltage gated channels will have two types of channels for each of the two different ions, what are they?

Note: Both are REQUIRED for the action potential

A

Na, K

57
Q

In action potentials, different ions move in opposing directions across the cell membrane. It creates a _____, or ion flow, which travels down the length of the cell membrane

A

Current

58
Q

Action potentials are often initiated by ______ at a different area of the membrane within the same cell

A

Graded Potentials

59
Q

Normally there are far more or far less voltage gated channels than chemically gated channels?

A

Far more voltage gated channels

60
Q

The 1st phase of action potential consisting of closed gated channels. Leaky channels still allow NA an K to move, ATPase move as well. Both maintain RMP.

A

Resting Potential

61
Q

Second phase of action potential consisting of depolarization, chemically gated channels open that initiates the phase which depolarizes membrane and causes Na+ voltage gated channels to open

(technically polarize cell with positive charge but call it depolarization)

A

Active Phase (aka Depolarization)

62
Q

Active phase where Na+ channels close, and the K+ voltage channels open. Causes K+ to flow out of the cell because of large collection of positive charges in interior of membrane (electrochemical gradient)

Chemically gated channels have already closed

A

Active Phase: Repolarization

63
Q

Final phase of action potential, K channels stay open a while and polarizes past RMP (more than -70 mV)

A

Active Phase: Hypoerpolarization

64
Q

Should RMP have a ______ amount of Na+ outside the cell and a ______ amount of K inside the cell

A

Higher Na+ outside the cell

Higher K+ inside the cell

65
Q

What returns Na+ ions that flowed into cell at depolarization to the outside of the cell to reestablish RMP at the end of action potential?

A

ATPase

66
Q

What are common characteristics of cells that conduct action potential

A

Long and thin cells

67
Q

Can the message go down the cell in two directions?

Give an example of tissue where it goes in two directions, and one example of tissue where the message goes in one direction

A

Yes.

Skeletal muscle - two directions

Nerve cell - one direction

68
Q

Refers to the fact that you must have enough stimulus (Na ions flowing across the membrane during depolarization) to open the voltage gated channels.

If there is not enough chemical stimulus, not enough sodium will enter the cell. Graded potential does not reach necessary stimulus to open voltage gated channels

A

Action Potential Threshold

69
Q

Once _______ channels open, the A.P. goes. It’s all or nothing.

A

Voltage gated channels

70
Q

Period of time where all ions need to be returned to baseline locations. Occurs after AP is completed, after hyperpolarizing or repolarizing the membrane. Refers to time when NA and K ATPases are working at restoring membrane back to original ion concentration

A

Refractory Periods

71
Q

Refractory period immediately after AP stimulus has passed through. Na and K ATPase haven’t had enough time to catch up

A

Absolute

72
Q

Occurs later than the absolute refractory period, Na and K ATPases have had a little time to work, a very large stimulus can generate an action potential along membrane

A

Relative Refractory Period

KN 251 (17 decks)

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