Action Potentials

Question 1

polarization

Answer 1

deviation from 0 mV

Question 2

depolarization

Answer 2

when membrane potential becomes more positive

Question 3

hyperpolarization

Answer 3

when membrane potential becomes more negative than resting potential

Question 4

repolarization

Answer 4

when membrane potential is returning towards resting potential

Question 5

action potential

Answer 5

a large depolarization that elicits a further depolarization and complete reversal of membrane potential across a plasma membrane

Question 6

graded potential

Answer 6

changes in membrane potential that vary in size, as opposed to being all-or-none; these are small and local; can be excitatory or inhibitory

Question 7

refractory period

Answer 7

hyperpolarization

Question 8

threshold

Answer 8

membrane potential at which action potential will certainly occur

Question 9

4 steps of an action potential

Answer 9

resting
depolarization
repolarization
hyperpolarization

Question 10

open channels

Answer 10

non gated channels that move ions down a concentration gradient
- ex: leak channels

Question 11

voltage gated channels

Answer 11

open in response to change in the membrane potential

Question 12

ligand gated channels

Answer 12

open in response to specific extracellular neurotransmitter

Question 13

signal gated channels

Answer 13

open in response to a specific intracellular molecule

Question 14

when does increased permeability of membrane to Na+ occur

Answer 14

depolarization

Question 15

during depolarization voltage gated Na+ channels open ____ and close after ____ delay

Answer 15

open rapidly

close after minimal delay

Question 16

voltage gated Na+ channels during:

• resting
• activation
• inactivation

Answer 16

• closed and inactive
• opens
• closes rapidly

Question 17

what happens to voltage gated Na+ channels at +30 mV

Answer 17

they close and become inactivated

Question 18

at what phase do voltage gated K+ channels slowly begin to open and increase membrane permeability to K+

Answer 18

repolarization

Question 19

differences between voltage gated K+ channels and K+ leak channels

Answer 19

voltage gated:

• ability to close
• more selective
• open from changes in membrane potential

Question 20

what causes hyperpolarization

Answer 20

voltage gated K+ channels stay open for a little too long

Question 21

absolute refractory period

Answer 21

sodium channels are either open or the inactivation gate is closed and cannot reopen; another action potential cannot be generated during this time
- (consists of depolarization and repolarization phases)

Question 22

relative refractory period

Answer 22

inactivation gate is open and activation gate is closed

• K+ permeability is still high
• (hyperpolarization phase)

Question 23

during hyperpolarization what happens to K+ permeability

Answer 23

decreases slowly

Question 24

during repolarization what happens to K+ permeability

Answer 24

increases slowly

Question 25

during depolarization what happens to Na+ permeability

Answer 25

increases rapidly

Question 26

during repolarization what happens to Na+ permeability

Answer 26

decreases rapidly

Question 27

hypokalemic periodic paralysis

Answer 27

periodic dips in blood K+ levels; membrane is hyperpolarized and it is harder to reach the threshold; cells need a bigger stimulus for an action potential

Question 28

hyperkalemic periodic paralysis

Answer 28

excessive levels of K+ in the blood; closer to threshold so little stimuli can cause action potentials; can be fatiguing for patients

• prolonged depolarization
• attacks managed by mild exercise