3A Resting Membrane And Action Potentials (Electrophysiology I)

Question 1

Must exist across membranes of cells for the signals to be sent to any cells

Answer 1

electrical potential

Question 2

electrical potential difference between the intracellular and extracellular fluid

Answer 2

membrane potential

Question 3

electrochemical state of the cell at rest; no net movement of any ions across the cells

Answer 3

resting membrane potential (rmp)

Question 4

rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane

Answer 4

action potential

Question 5

RMP of a large nerve fiber

Answer 5

-90mV

Question 6

formation of RMP depends on:

Answer 6

• concentration gradient or concentration difference of an ion
• permeability of the ion across the cell membrane

Question 7

main workforce responsible for establishing concentration gradients of K and Na

Answer 7

sodium potassium pump

Question 8

concentration of Na and K intracellularly

Answer 8

Na = 10mEq/L
K = 140mEq/L

Question 9

concentration of Na and K extracellularly

Answer 9

Na = 142mEq/L
K = 4mEq/L

Question 10

K moves out of the cell to equalize the concentration and diffuses extracellularly through what channel?

Answer 10

potassium leak channel

Question 11

moving out of K out of the cell causes the cytoplasm of the cell to be

Answer 11

electronegative since anions( negatively charged) the only ions left

Question 12

exact point where the K moving out of the cell due to concentration gradient, equals the K moving back into the cell because of the electrical gradient

Answer 12

Equilibrium or Nernst Potential

Question 13

electrical potential needed to attract K back into the cell to balance the concentration gradient

Answer 13

-94mV

Question 14

used to calculate the diffusion potential when the membrane is permeable to SEVERAL DIFFERENT IONS

Answer 14

goldman equation

Question 15

Keeps cells in “ready state” to fire an action potential

Answer 15

resting membrane potential

Question 16

threshold potential

Answer 16

-55mV

Question 17

channel that causes both depolarization and repolarization

Answer 17

voltage gated sodium channels

Question 18

2 gates of voltage gated SODIUM channels

Answer 18

• activation gate - near the outside

* inactivation gate - near the inside

Question 19

channel that increases rapidity of repolarization

Answer 19

voltage gated potassium channel

Question 20

T/F: it is usually not possible without first repolarizing the nerve fiber in order for Na channels to open again

Answer 20

TRUE

Question 21

Stages of Voltage gated Sodium Channels

Answer 21

1. Resting stage -90mV
2. Activation stage -90mV to +35mV
3. Inactivation stage +35 to -90mV

Question 22

Stages of Voltage gated potassium channels

Answer 22

1. Resting stage

2. Slow Activation

Question 23

period when voltaged gated sodium channel closes and the voltage gated potassium channels open

Answer 23

repolarization stage

Question 24

stage wherein reestablishes the normal negative resting membrane potential

Answer 24

repolarization stage

Question 25

excess exit of potassium which leads to the potential being more negative than the RMP

Answer 25

hyperpolarization

Question 26

this is where the RELATIVE REFRACTORY PERIOD occurs, membrane potential returns to RMP throught the normal action of N/K pump

Answer 26

RECOVERY

Question 27

stage wherein absolute refractory period occurs

Answer 27

repolarization

Question 28

this is where the membrane returns to its Resting membrane potential

Answer 28

repolarization

Question 29

the transmission of the depolarization process along the nerve or muscle fiber

Answer 29

impulse

Question 30

recite the PROPAGATION OF ACTION POTENTIAL

clue: 1st step-VGNC opens

Answer 30

VGNC opens –> positive charges move through the nerve –> positive feedback occurs –> VGNC’s adjacent areas open –> propagation of the action potential –> VGKC opens slowly –> repolarization –> return to RMP

Question 31

principle in which the voltage must be high or equal to that of the threshold potential in order for an action potential to occur

Answer 31

ALL OR NOTHING PRINCIPLE

Question 32

where a stimulation does not generate enough voltage to stimulate the NEXT AREA OF THE MEMBRANE

Answer 32

subthreshold potential

Question 33

the spread of the depolarization stops at this point

Answer 33

subthreshold potential

Question 34

this begins at the upstroke until the end of the downstroke of the action potential or repolarization

Answer 34

ABSOLUTE REFRACTORY PERIOD

Question 35

voltage gated sodium channels are inactivated at this point and no amount of stimulus will activate it

Answer 35

absolute refractory period

Question 36

action potential cannot be elicited at his time regardless of the stimulus strength

Answer 36

absolute refractory period

Question 37

an action potential can be elicited at this period but stimulus should be greater than the threshold potential

Answer 37

RELATIVE REFRACTORY PERIOD

Question 38

also known as CONTINUOUS CONDUCTION

Answer 38

non-saltatory conduction (applies the all or nothing principle)

Question 39

slower conduction velocity

Answer 39

non-saltatory period

Question 40

faster conduction velocity

Answer 40

saltatory period

Question 41

conduction that involves activation of adjacent voltage-gated sodium channels

Answer 41

non-saltatory conduction

Question 42

conduction that increases velocity of nerve transmission in myelinated fibers as much as 5- to 50- fold

Answer 42

saltatory conduction

Question 43

electrical insulator absent –> charges leak out –> decrease in voltage –>adjacent channels not stimulated –> action potential stops

Answer 43

non-saltatory conduction

Question 44

action potential goes through fewer voltage-gated Na channels –> faster transmission of impulse + energy conserved –> subsequent activation of succeeding nodes

Answer 44

saltatory conduction

Question 45

this membrane potential change is responsible for the start of an action potential

Answer 45

threshold potential

Question 46

T/F: resting membrane potential is solely dependent on the equilibrium potential of potassium

Answer 46

false

Question 47

T/F: during hyperpolarization, a cell cannot be stimulated to form an action potential

Answer 47

false