The Resting Membrane Potential - Lecture 4

Question 1

Fill in the blank
The Plasma membrane of all cells are _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _

Answer 1

Polarised Electrically

Question 2

What is the symbol for a membrane potential?

Answer 2

Em

Question 3

What is the definition of membrane potential?

Answer 3

A separation of opposite charges across the membrane.

Question 4

What are the units used for membrane potentials?

Answer 4

Units: mV (1/1000 volt)

Question 5

Is the membrane itself charged during membrane potentials?

Answer 5

No - Em refers to the difference in charge between the thin layers of ECF and ICF located next to the inside and outside of the membrane

Question 6

Why is the Em different between different cells?

Answer 6

Em relies on the permeability of key ions

Question 7

What is a rapid transient change in their membrane potential?

Answer 7

An Action potential

Question 8

What cells can produce an action potential?

Answer 8

Nerve and muscle cells

Question 9

What is a resting membrane potential?

Answer 9

The constant membrane potential while the cell is at rest

Question 10

What ions is the cell membrane permeable to?

Answer 10

Potassium

Sodium - only very slightly.

Question 11

What fluid is sodium found in most abundance?

Answer 11

Extracellular fluid - It is generally transported into the cell

Question 12

What fluid is potassium found in most abundance?

Answer 12

Intracellular fluid

Question 13

What fluid is chlorine found in most abundance?

Answer 13

Extracellular

Question 14

How is the Em created?

Answer 14

Due to unequal distribution of ions and their selective movement through the plasma membrane

Question 15

What is the concentration gradient of Potassium?

Answer 15

Out of cells

Question 16

What is the concentration gradient of Sodium?

Answer 16

Into cells

Question 17

How many more times is Potassium permeable to the membrane than sodium at the resting potential?

Answer 17

100 more times

Question 18

What is the cell membrane impermeable to?

Answer 18

Large negatively charged intracellular proteins

Question 19

What is the effect of Potassium movement on the Em

Answer 19

Inside the cell becomes more negative. Outside the cell becomes more positive

Question 20

What are the two opposing forces acting on Potassium?

Answer 20

The concentration gradient (tending to move K+ out of the cell)
The electrical gradient (tending to move K+ into the cell)

Question 21

When does Potassium movement stop?

Answer 21

When both electrical gradient and concentration gradient are at equilibrium

Question 22

What is the symbol for the equilibrium potential of Potassium?

Answer 22

Ek

Question 23

What value of the Ek of Potassium?

Answer 23

-90mV

Question 24

What is the nernst equation used for?

Answer 24

Is it used for calculating the equilibrium potential for any given ion

Question 25

What is the Nernst equation?

Answer 25

Eion= 61log10 [Conc ionOutside] ---------------------- [Conc Ion Inside]

Question 26

What occurs when sodium is transported into the cell

Answer 26

The Extracellular fluid becomes more negative Inside the cell becomes more positive Concentration gradient into the cell

Question 27

What occurs as permeability to an ion increases?

Answer 27

There is a tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential.

Question 28

Is the membrane potential positive or negative at rest?

Answer 28

Negative

Question 29

Is the membrane potential at rest close to that of K or Na ?

Answer 29

Closer to Potassium at rest

Question 30

What is the Golman-Hodkin- Katz equation for?

Answer 30

It is an equation used to calculate the membrane potential of a cell - It takes into account all ions present and their permeabilities Em = 61log10 PermxConc Ionout -------------------------- PermxConcion In

Question 31

In the sodium potassium pump what is the ratio of Sodium exchanged for Potassium exchanged?

Answer 31

3 Sodium exported 2 Potassium entering

Question 32

What type of current does the Sodium Potassium pump create?

Answer 32

It creates a hyperpolarising current

Question 33

What is the value of E (na)?

Answer 33

+ 61 mV

Question 34

What is the value of E(k) ?

Answer 34

-90mV

Question 35

In the pancreas what are changes in membrane potentials linked to?

Answer 35

Changes in Em linked to secretion of insulin from pancreatic Beta-cells.

Question 36

What is the Goldman-Hodgkin-Katz equation?

Answer 36

Vm = Perm of ion1[Ion1Outisde] + Perm of ion2[Ion2Outside] ----------------------------------------------------------------- Perm of ion1[Ion1Inside] + Perm of ion2[Ion2Inside]