Membrane potential

Question 1

Define membrane potential?

Answer 1

Separation of opposite charges across the membrane

Question 2

What do excitable cells have?

Answer 2

(nerve and muscle) ability to produce rapid, transient changes in their membrane potential when excited (action potentials).

Question 3

Describe resting membrane potential in different cell types?

Answer 3

constant in non-excitable cells, and in excitable cells at rest

Question 4

What is the concentration gradient of K?

Answer 4

Outward

Question 5

What is the concentration gradient of Na?

Answer 5

Inward

Question 6

At resting membrane potential the membrane is …. more permeate to …than …?

Answer 6

100x
K+
Na+

Question 7

What are the opposing forces acting on K+?

Answer 7

1) Concentration gradient (tending to move K+ out of the cell)
2) The electrical gradient (tending to move K+ into the cell)

Question 8

What is the potential for K known as when forces are directly balanced?

Answer 8

Equilibrium potential for K+ (Ek)

Question 9

What is Ek?

Answer 9

-90mV

(the polarity of the excess charge on INSIDE of the membrane

Question 10

What is the nernst equation?

Answer 10

equilibrium potential for any given ion can be calculated using the Nernst equation.

Eion= 61log10(ion(O)/ion(i))

Question 11

What happens when the permeability for a given ion is high?

Answer 11

the greater the tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential.

Question 12

What are all cells inside at resting membrane potential?

Answer 12

Negative

Question 13

What equation can be used to calculate Em?

Answer 13

goldman-hodgkin-katz equation

Question 14

What is the effect of the Na+/K+ mum on K+ and Na_ gradients?

Answer 14

Helps maintain them

Since its stoichiometry is 3Na+ exported for every 2K+ entering, the pump will generate a hyperpolarizing current.

Question 15

How much does the Na/K pump add to Em?

Answer 15

In skeletal muscle, it adds only 2-3mV to Em but in other cell types it can add +10mV, depending upon the resistance of the membrane and pump activity.

Question 16

Describe the specialised use of Em in nerve and muscle cells?

Answer 16

Rapidly and transiently alter their membrane permeabilities in response to appropriate stimulation, resulting in fluctuations in Em.

Nerve impulses in nerve cells and triggering contraction in muscle cells.
-Changes in Em linked to secretion of insulin from pancreatic B-cells.