Membrane Potential and Excitation

Question 1

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

Answer 1

Potential

Question 2

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

Answer 2

Kinetic Energy

Question 3

The force which slows down current flow.

Answer 3

Resistance

Question 4

A substance which inhibits current flow

Answer 4

Insulator

Question 5

A substance which promotes current flow

Answer 5

Conductor

Question 6

Current = ?

Answer 6

V/R

Question 7

Why does current flow occur in living systems?

Answer 7

Ions flow!

Question 8

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

Answer 8

Membrane - separates charges

Question 9

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

Answer 9

Channels

Question 10

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

Answer 10

Passive Channels

Question 11

Gated channels that only open when stimulated

Answer 11

Active Channels

Question 12

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

Answer 12

Chemically gated channel

Question 13

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

Answer 13

Voltage Gated Channel

Question 14

Current flow depends on two factors. What are they?

Answer 14

Electrical Charge Movement

Chemical Diffusion

Question 15

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

Answer 15

Electrical Charge Movement

Question 16

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

Answer 16

Chemical Diffusion

Question 17

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

Answer 17

Electrochemical Gradient

Question 18

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

Answer 18

Electrochemical Gradient

Question 19

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.

Answer 19

Resting Membrane Potential

Question 20

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

Answer 20

Resting Membrane Potential

Question 21

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

Answer 21

Polarization of the membrane

Question 22

What are the units of charge separation?

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

Answer 22

millivolts

Inside with respect to outside

Question 23

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

Answer 23

-70mV

Question 24

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

Answer 24

At the membrane

Question 25

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

Answer 25

Polarization

Question 26

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

Answer 26

Capable Fixed. Only positively charged ions can move.

Question 27

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

Answer 27

ATPase pump

Question 28

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

Answer 28

3Na+ pumped out 2K pumped in

Question 29

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

Answer 29

antiport, 5

Question 30

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

Answer 30

!

Question 31

Pumping prevents what from being reached?

Answer 31

Equilibrium

Question 32

How does it prevent equilibrium?

Answer 32

Prevents equilibrium from being reached to reach electrochemical gradient

Question 33

Are there more or less K and Na passive channels in the plasma membrane? How else is it maintained?

Answer 33

K channel>Na channel K can move more freely out of the membrane

Question 34

Why does K move outside the cell?

Answer 34

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

Question 35

Why does Na want to move in?

Answer 35

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

Question 36

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

Answer 36

Because of the force of the concentration gradient

Question 37

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

Answer 37

Gated Channels

Question 38

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

Answer 38

Gated Channels

Question 39

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

Answer 39

Small, RMP stays the same.

Question 40

Cells that cannot alter potential do not have

Answer 40

Gated Channels

Question 41

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

Answer 41

Polarized Cell

Question 42

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

Answer 42

Depolarized Cell

Question 43

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

Answer 43

Hyperpolarized Cell

Question 44

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

Answer 44

Repolarized Cell

Question 45

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

Answer 45

Decrease Increase

Question 46

Two types of mechanisms of change in plasma membrane potential

Answer 46

Graded Potential | Action Potential

Question 47

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

Answer 47

Graded Potential and Action Potential

Question 48

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?

Answer 48

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

Question 49

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

Answer 49

Graded potential

Question 50

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

Answer 50

Action potential

Question 51

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

Answer 51

Graded potentials

Question 52

Is the area that changes potential large or small in graded potentials? Do many or a few ions move across the membranes?

Answer 52

small A few

Question 53

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

Answer 53

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

Question 54

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

Answer 54

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

Question 55

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

Answer 55

Voltage-gated channels.

Question 56

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

Answer 56

Na, K

Question 57

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

Answer 57

Current

Question 58

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

Answer 58

Graded Potentials

Question 59

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

Answer 59

Far more voltage gated channels

Question 60

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.

Answer 60

Resting Potential

Question 61

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)

Answer 61

Active Phase (aka Depolarization)

Question 62

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

Answer 62

Active Phase: Repolarization

Question 63

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

Answer 63

Active Phase: Hypoerpolarization

Question 64

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

Answer 64

Higher Na+ outside the cell | Higher K+ inside the cell

Question 65

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?

Answer 65

ATPase

Question 66

What are common characteristics of cells that conduct action potential

Answer 66

Long and thin cells

Question 67

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

Answer 67

Yes. Skeletal muscle - two directions Nerve cell - one direction

Question 68

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

Answer 68

Action Potential Threshold

Question 69

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

Answer 69

Voltage gated channels

Question 70

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

Answer 70

Refractory Periods

Question 71

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

Answer 71

Absolute

Question 72

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

Answer 72

Relative Refractory Period