Physiology- Origin of Membrane Potentials

Question 1

Membrane potential (Em)

Answer 1

separation of opposite charges across the membrane (mV)

Caused by difference in conc and permeability of key ions

Difference in change ofECF and ICF- not the membrane itself

Question 2

What can nerve and muscle do when excited?

Answer 2

produce rapid, transient changes in their membrane potential ie create action potentials

Question 3

Resting membrane potential is constant in excitable and non-excitable cells at rest. T/F?

Answer 3

True

Question 4

Extracellular conc of Na+

Answer 4

150mM

Question 5

Extracellular conc of K+

Answer 5

5mM

Question 6

Extracellular conc of A-

Answer 6

0mM

Question 7

Extracellular conc of Cl-

Answer 7

110mM

Question 8

Intracellular conc of Na+

Answer 8

15mM

Question 9

Intracellular conc of K+

Answer 9

150mM

Question 10

Intracellular conc of A-

Answer 10

65mM

Question 11

Intracellular conc of CL-

Answer 11

7mM

Question 12

Relative permeability of Na+

Answer 12

1mM

Question 13

Relative permeability of K+

Answer 13

100mM in skeletal muscle

Question 14

Relative permeability of

Answer 14

0mM

Question 15

Relative permeability of

Answer 15

n/a

Question 16

Direction of conc gradient for Na+

Answer 16

inward

Question 17

Direction of conc gradient for K+

Answer 17

outward

Question 18

Why it the electrical gradient for Na+ and K+ always towards the negatively charged side of the membrane?

Answer 18

they are both cations (positively charged)

Question 19

How many more times permeable is K+ than Na+ at resting membrane potential?

Answer 19

100x

Question 20

What type of particles is the plasma membrane impermeable to?

Answer 20

large, negatively charge ic proteins (A-)

Question 21

What two opposing forces act on K+?

Answer 21

the concentration gradient (outwards)

the electrical gradient (inwards)

Question 22

Equilibrium potential

Answer 22

when conc gradient = electrical gradient

no further net movement occurs

Question 23

Equilibrium potential of K+

Answer 23

-90mV

Question 24

Nernst equation

Answer 24

Eion=61log10([ion]o/[ion]i)

Question 25

Equilibrium potential of Na+

Answer 25

+61mV

Question 26

Effect of increasing permeability of an ion on tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential

Answer 26

Increases tendency

Question 27

Ek of inside of all cells at rest

Answer 27

negative (~-70mV on typical nerve cell)

Question 28

Em=Ek. T/F?

Answer 28

False

due to slight inward leak of Na+ into cell

Question 29

What is the single most important factor in setting Em?

Answer 29

K+ gradient