Resting Membrane Potential

Question 1

What is the resting membrane potential of a nerve cell?

Answer 1

-70mV (inside vs outside)

Question 2

Why is the resting membrane potential of a nerve cell -70mV?

Answer 2

• uneven distribution of charged particles on either side of cell membrane
• cell membrane is only selectively permeable to ions

Question 3

Reasons for the development of the resting membrane potential?

Answer 3

• organic anions (proteins are - charged)
• Na+/K+ pump (exchanges 3 Na+ out for 2 K+ in)
• membrane permeability: more permeable to K+ than Na+ as more channels for K+
• equilibrium potentials

Question 4

What do chemical + electrical gradients do?

Answer 4

These are two types of forces that influence the movement of ions across the plasma membrane.

Question 5

What happens in a chemical gradient?

Answer 5

Ions pass from high to low conc - specific for each ion.
- Na+ into cell
- K+ out of cell

Question 6

What happens in a electrical gradient?

Answer 6

Ions pass to areas of opposite charge.
- Na+ & K+ want to move into cell

Question 7

What is the electrochemical gradient?

Answer 7

The balance of forces acting upon an ionic species.
- Na+ : electrical & chemical gradient attract Na+ into cell
- K+ : chemical (out) & electrical (in), oppose one another

Question 8

What is the equilibrium potential of an ion?

Answer 8

The voltage achieved when the plasma membrane is exclusively permeable to that ion.

Question 9

When does the equilibrium potential of an ion occur?

Answer 9

When the chemical gradient force is equal and opposite to the electrical gradient force.

Question 10

What would happen if the membrane was only freely permeable to Na+?

Answer 10

Na+ enters cell until chemical & electrical gradients are balanced.

Question 11

What would happen if the membrane was only freely permeable to K+?

Answer 11

K+ leaves cell until the chemical & electrical gradients are balanced.

Question 12

What are ion channels?

Answer 12

Proteins spanning the lipid membrane.
Determines the permeability of the membrane to the ion, & its influence on the membrane potential.

Question 13

What are the two types of channels?

Answer 13

• passive (leak) channels
• gated (active) channels

Question 14

What do passive channels do?

Answer 14

• always partially open (ions can move in/out)
• contribute to the resting membrane potential

Question 15

What do gated channels do?

Answer 15

Open/close in response to specific stimuli

Question 16

What 3 possible states do gated channels exist in?

Answer 16

• activatable: close but capable of opening
• activated: open
• refractory: closed + incapable to open

Question 17

What are the 3 main types of gated channels?

Answer 17

• chemically regulated
• voltage regulated
• mechanically regulated