Resting Potential & Action Potential

Question 1

define

ion channel

Answer 1

an opening (pore) formed by 4-6 membrane spanning protein molecules embedded in cell membrane

Question 2

the diameter of an ion channel determines ____

Answer 2

ion selectivity

Question 3

what is gating?

Answer 3

the property of ion channels to open & close depending on changes in cell membrane

Question 4

functional states of ion channels

Answer 4

• closed & activatable (at rest)
• open (active)
• closed & non-activatable (refractory, inactive)

Question 5

types of gated ion channels

Answer 5

1. ligand (chemical transmitor)
2. phosphorylation
3. voltage
4. mechanically

Question 6

resting membrane potential is determined by ____

Answer 6

non-gated ion channels (always open)

Question 7

what is the typical RMP?

Answer 7

-70mV (-40 to -90mV)

Question 8

depolarization

mV

Answer 8

> -70mV (more positive)

Question 9

hyperpolarization

mV

Answer 9

< -70mV (more negative)

Question 10

what channels are active at RMP?

Answer 10

• leak channels
• Na/K pump

Question 11

describe the actions of ion channels during RMP

Answer 11

• more K non-gated channels than Na channels (K leaks out, some Na leaks in)
• Na/K pumps 3Na out, 2 K in
• creates more negative inside

Question 12

ion distribution in motor neuron at rest

Answer 12

• ECF: Na+, Cl-
• ICF: K+, organic anions (-)

Question 13

define

equilibrium potential

Answer 13

what would happen if each ion was able to move in or out of cell in absence of the others

Question 14

equilibrium potential: Na+

Answer 14

+55mV

Na+ would enter

Question 15

equilibrium potential: K+

Answer 15

-75mV

K+ would exit

Question 16

equilibrium potential: Cl-

Answer 16

-60mV

Cl- would enter

Question 17

permeability is determined by ____

Answer 17

number of non-gated ion channels present in the membrane

Question 18

the permeability of (Na/K) is higher than (Na/K)

Answer 18

K>Na

Question 19

the concentration gradient is maintained by the ____

Answer 19

Na/K pump

Question 20

the Na/K pump sends ____ Na+ out and ____K+ in

Answer 20

3Na out, 2K in

Question 21

why is RMP closer to the equilibrium of K?

Answer 21

• more K goes out, some Na goes in
• closer to K equilibrium of -75mV

Question 22

the Na/K pump moves ions ____ their concentration gradient

Answer 22

against