Membrane potential

Question 1

2 ways membrane potentials can develop

Answer 1

active transport and diffusion

Question 2

Describe how the sodium-potassium exchange pump works

Answer 2

The sodium-potassium pump system moves sodium and potassium ions against large concentration gradients. It moves two potassium ions into the cell where potassium levels are high, and pumps three sodium ions out of the cell and into the extracellular fluid.

Question 3

How many sodium ions are
transported and in which direction? How many potassium ions are transported and in which direction?

Answer 3

In each cycle, three sodium ions exit the cell, while two potassium ions enter.

Question 4

Does it move against a concentration gradient

Answer 4

The sodium and potassium move against the concentration gradients

Question 5

What are cations?

Answer 5

Cations are ions that are positively charged

Question 6

anions

Answer 6

ions that are negatively charged

Question 7

What are examples of anions found just inside of the cell membrane? Do they typically move out of the cell or stay put?

Answer 7

organic phosphates, sulfates, protein anions *typically stay put

Question 8

In which direction would the sodium ions diffuse, if they could diffuse?

Answer 8

out

Question 9

In which direction would the potassium ions diffuse, if they could diffuse?

Answer 9

in

Question 10

Nernst potential

Answer 10

the ratio of the tendency for ions to diffuse in one direction versus another

Question 11

what is the nernst potential of sodium ions in our cell membrane example

Answer 11

+61mV

Question 12

what is the nernst potential of potassium ions in our cell membrane example?

Answer 12

-94mV

Question 13

The original development of the membrane potential is by

Answer 13

active transport

Question 14

n the resting cell membrane, immediately inside of the cell membrane are more _________ charges than ____________ charges

Answer 14

negative; positive

Question 15

A negative membrane potential may be re-established by

Answer 15

diffusion

Question 16

What is an action potential

Answer 16

Action potentials (those electrical impulses that send signals around your body) are nothing more than a temporary shift (from negative to positive) in the neuron’s membrane potential caused by ions suddenly flowing in and out of the neuron.

Question 17

Name 3 ways in which an action potential may be elicited in a nerve fiber?

Answer 17

electric stimulation, mechanical compression, application of chemicals to the membrane

Question 18

The action potential occurs when the membrane becomes more permeable to _____________ ions. These will diffuse in which direction, into or out of the cell?

Answer 18

sodium; out

Question 19

what is depolarization

Answer 19

movement of a cell’s membrane potential to a more positive value (i.e. movement closer to zero from resting membrane potential). When a neuron is depolarized, it is more likely to fire an action potential.

Question 20

What channels open in depolarization

Answer 20

Na+

Question 21

What channels are closed in depolarization

Answer 21

K+

Question 22

What happens to the membrane potential in depolarization

Answer 22

it reverses and goes above zero

Question 23

What ions are moving during depolarization and in what direction

Answer 23

Na+ ions in

Question 24

Is nernst potential achieved during depolarization

Answer 24

no

Question 25

What is the reversal potential

Answer 25

the positive potential that develops momentarily inside the fiber

Question 26

Define repolarization

Answer 26

the excessive + charges inside the fiber are transferred back out of the fiber & normal - resting membrane potential returns

Question 27

what causes repolarization

Answer 27

by the closing of sodium ion channels and the opening of potassium ion channels.

Question 28

What channels are open in repolarization

Answer 28

K+

Question 29

What channels close during repolarization

Answer 29

Na+

Question 30

what happens to the membrane potential during repolarization

Answer 30

re-established

Question 31

what ions are moving and in what direction duing repolarization

Answer 31

K+ out

Question 32

Is nernst potential achieved in repolarization

Answer 32

yes

Question 33

are there more sodium ions inside the cell or outside at the end of repolarization

Answer 33

in

Question 34

are there more potassium ions inside the cell or outside at the end of repolarization

Answer 34

out

Question 35

did the membrane potential just become re-established after repolarization

Answer 35

yes

Question 36

what are 2 different types of channels

Answer 36

Na+ and K+

Question 37

at rest, sodium channels are almost completely

Answer 37

closed

Question 38

at rest, potassium channels are

Answer 38

partially open

Question 39

after potential

Answer 39

brief hyperpolarization period following the action potential

Question 40

Is after potential hyperpolarized or hypopolarized

Answer 40

hyperpolarized

Question 41

what causes the after potential

Answer 41

the efflux of K+

Question 42

did this ion reach its nernst potential during after potential

Answer 42

yes

Question 43

absolute refractory period

Answer 43

period of time of complete insensitivity to another stimulus

Question 44

can a greater-than-threshold strength stimulus initiate another action potential

Answer 44

no because it cant respond unless ready (flushing toilet)

Question 45

relative refractory period

Answer 45

near end of repolarization phase

Question 46

can a greater-than-threshold strength stimulus initiate another action potential

Answer 46

Yes, because it is below resting membrane potential

Question 47

In what direction do action potentials travel

Answer 47

all directions

Question 48

what is the all or none principle

Answer 48

strength by which nerve/muscle responds to stimulus

Question 49

what is a subthreshold stimulus

Answer 49

stimulus to small to produce action potential

Question 50

what are graded or local potentials?

Answer 50

short lived local changes in membrane potential

Question 51

Can graded or local potentials spread far from the area surrounding the site of stimulation

Answer 51

no

Question 52

can graded or local potentials summate

Answer 52

no

Question 53

what is a threshold stimulus

Answer 53

minimum stimulus needed to achieve action potential

Question 54

does a greater-than-threshold stimulus result in an action potential with greater amplitude

Answer 54

no

Question 55

If the stimulus strength increases, then action potential frequency will

Answer 55

increase

Question 56

Epsp

Answer 56

excitatory postsynaptic potential

Question 57

Ipsp

Answer 57

inhibitory postsynaptic potential

Question 58

What usually results in Na+ gate opening

Answer 58

epsp

Question 59

what usually results in K+ gate opening

Answer 59

ipsp

Question 60

If the membrane becomes hypopolarized, does this increase or decrease the chance that summation may result in an action potential

Answer 60

increase

Question 61

if the membrane becomes hyperpolarized does this increase or decrease the chance that summation may result in an action potential

Answer 61

decrease