Action Potential

Question 1

action potentials begin

Answer 1

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

Question 2

graded potentials

Answer 2

changes in membrane potential that are small and local

excitatory or inhibitory

Question 3

strength of initial graded potential correlates with

Answer 3

strength of triggering event

Question 4

graded potentials dissipate with distance because

Answer 4

K+ leak channels are always open (basically)

Question 5

phase 4

Answer 5

resting phase

Question 6

phase 0

Answer 6

depolarization

Question 7

Phase 3

Answer 7

re-polarization

Question 8

hyperpolarization

Answer 8

refractory period (extra negative)

Question 9

threshold

Answer 9

membrane potential at which AP will certainly occur

Question 10

ion channel characteristics

Answer 10

mostly passive
leaky
gates restrict ion movements (voltage-gated, ligand-gated, signal-gated, mechanically-gated)

Question 11

depolarization mechanism

Answer 11

increase in permeability of membrane to Na
voltage-gated Na channels open rapidly
after MINIMAL delay, channels close automatically

Question 12

Na leak channel gates

Answer 12

activation gate (threshold opens this) 
inactivaiton gate (closes pore after a slight delay)

Question 13

phases of voltage gated Na channels opening

Answer 13

resting - A closed I open
Activation - A open I open
Inactivation - A open I closed
cannot be moved until membrane potential returns to near resting

Question 14

positive feedback loop of voltage-gated Na channels

Answer 14

local triggering opens some channels
More Na channels open
More spread
Loop is broken at +30mV because Na channels close

Question 15

absolute refractory period

Answer 15

Na channels are either open or the inactivation gate is closed and cannot reopen
another Ap cannot be generated

Question 16

relative refractory period

Answer 16

inactivation gate is open and activation gate is closed
K+ permeability is fairly high and overshoots K leaving the cell, membrane becomes slightly more negative than resting membrane potential

AP may be stimulate but requires stronger stimulus

Question 17

what three events occur at threshold potential

Answer 17

rapid opening of voltage gated Na channel activation gates
Slow closing of voltage gated Na channel inactivation gates
Slow opening of voltage gated K channel gates

Question 18

hypokalemic periodic paralysis

Answer 18

periodic dips in blood K levels
Dorps in blood K triggers events, but blood K levels are normal between attacks
membrane hyperpolarized, harder to reach threshold
repolarizatino occurs more quickly

Question 19

Hyperkalemic periodic paralysis

Answer 19

excessive K+ in blood
unable to compensate like normal person would
prolonged depole and absolute refractory periods
attacks managed by mild exercise, potassium-wasting diuretics, glucose management

Question 20

permeability to sodium increases ______ while potassium permeability is _____

Answer 20

increases rapidly

K permeability is slower to increase