Session 4.1: Resting Membrane Potential

Question 1

what is a membrane potential

Answer 1

voltage(the electrical charge) that exists across their plasma membrane or mitochondrial membrane
measures potential inside relative to extracellular

Question 2

how is membrnae potential measured

Answer 2

one electrode in intermembrane space and one in cell
voltmeter
the microelectrode used is a fine glass pipette which can penetrate cell membrane
the cell membrane is filled with conducting solution (KCl)

Question 3

what are membrane potentials measured in

Answer 3

millivolts (mV)

x10-3V

Question 4

what resting potential do animal cells usually have

Answer 4

-20 - -90mV

Question 5

what cells have the largest resting potentials

Answer 5

cardiac and skeletal (-80 - -90mV)

Question 6

what resting potentials do have nerve cells have

Answer 6

-50 - -70mV

Question 7

what is resting membrane potential in cardiac myocytes

Answer 7

-80mV

Question 8

what is resting membrane potential in neurones

Answer 8

-70mV

Question 9

what is resting membrane potential in skeletal muscle myocytes

Answer 9

-90mV

Question 10

what is resting membrane potential in smooth muscle myocytes

Answer 10

-50mV

Question 11

what are ion channels

Answer 11

proteins that enable ions to cross cell membranes

have an aqueou pore for ions to flow by diffusion

Question 12

what are ion channel properties

Answer 12

selective
gated (conformational change)
ions down electrochemical gradient v rapidly

Question 13

in which directions does potassium move

Answer 13

towards outside

Question 14

how do potassium ions leave the cell

Answer 14

through potassium channels

Question 15

how is a membrane potential created

Answer 15

potassium ions leave the cell
anions remain in the cell
negative charge created inside the cell, and positive outside

Question 16

what opposes potassium’s movement

Answer 16

electrical gradient for potassium is inwards
so if electrical and chemical gradient equal and opposite then no net movement of K but there will be negative memrbane potential

Question 17

how is a resting membrane potential maintained

Answer 17

despite possible opposite and equal gradient, the memrbane is still selectively permable to K which leak out

Question 18

how is the electrical gradient determined

Answer 18

voltage x valency (=+1 for K+) x faraday’s no

Question 19

how is the chemical gradient determined

Answer 19

gas constant x temperature x ln(conc on outside/conc on inside)

Question 20

when is there no outward force for k+

Answer 20

at equilibrium

so the equations equal each other

Question 21

what is the nernst equation for potassium

Answer 21

V= RT/valency x faraday x ln x(conc on outside/conc on inside)

Question 22

RT/F can also mean

Answer 22

61

Question 23

what is the nernst equation

Answer 23

allows you to calculate the membrane potential at which K+ will be in equilibrium, given the extracellular and intracellular k+
can write for any ion

Question 24

what others ion leak through the membrane

Answer 24

sodium and calcium inward

diminish size of negative memrbane potenital inside the cell

Question 25

what is the membrane potential inside the cell

Answer 25

-70mV

Question 26

what other channels does skeletal muscle have

Answer 26

chloride which goes inside cell, increasing size of negative charge (nearer -95mV)

Question 27

why do nerve cells and cardiac muscles not have the same membrane potential (Ek)

Answer 27

the membrane is not perfectly selective for K+

Question 28

why do smooth muscle cells ahve a much lower resting potential

Answer 28

lower selectivity for K+ and more contribution from other channels

Question 29

why do skeletal muscles have a much higher resting potential

Answer 29

many cl- and K+ channels open