M&R Session 3- The Resting Cell Membrane

Question 0

What is a resting membrane potential measured by?

Answer 0

A microelectrode that contains a conducting solution and penetrates the cell membrane.

Question 1

What is a resting membrane potential?

Answer 1

It is the difference in potential across a plasma membrane.

Question 2

What is the range of RMPs for animal cells?

Answer 2

-20mV to -90mV

Question 3

What is the range of RMPs for cardiac and skeletal muscle?

Answer 3

-80mV to -90mV

Question 4

What is the range of RMPs for nerve cells?

Answer 4

-50mV to -75mV

Question 5

What is the most typical RMP for a nerve cell?

Answer 5

-70mV

Question 6

How does membrane permeability arise?

Answer 6

The prescence of channels and transport proteins that span the membrane.

Question 7

What equation can be used to find out the equilibrium potential for a particular ion?

Answer 7

The Nernst equation.

Question 8

Why is the RMP often very close to the equilibrium potential for potassium?

Answer 8

Potassium channels are often open and therefore dominate the resting permeability.

Question 9

Why is the RMP not exactly the equilibrium potential of potassium?

Answer 9

The membrane is not perfectly selective; it is leaky to other ions as it may have other ion channels present.

Question 10

What happens to the membrane potential if you increase the permeability to a particular ion?

Answer 10

It will move closer to the equilibrium potential of that ion.

Question 11

Define depolarisation. What happens to the cell interior?

Answer 11

A decrease in the membrane potential from its normal value.

The cell interior becomes less negative.

Question 12

Define hyperpolarisation. What happens to the cell interior?

Answer 12

It is an increase in the membrane potential size from its normal value.
The cell interior becomes more negative.

Question 13

Which two ions depolarise the RMP?

Answer 13

Calcium and sodium.

Question 14

Which two ions hyperpolarise the RMP?

Answer 14

Potassium and chloride ions

Question 15

What does the extend of ion contribution to the membrane potential depend upon? (2)

Answer 15

• the number of channels for that ion

- the permeability of the membrane for that ion

Question 16

Which equation approximates what will happen to the membrane potential when all ions contributions have been taken into account?

Answer 16

The Goldman-Hodgkin-Katz equation

Question 17

What is membrane selectivity determined by? (2)

Answer 17

• the number of channels open

- the number of channel types

Question 18

What 3 ways are channels gated in?

Answer 18

• voltage gated
• ligand gated
• mechanically gated

Question 19

What happens in fast synaptic transmission?

Answer 19

The receptors are also the ion channels.
Depolarising transmitters open positive channels and therefore cause an excitatory response- excitatory postsynaptic potential
Hyperpolarising transmitters open negative channels and therefore cause an inhibitory response- inhibitory postsynaptic potential

Question 20

What happens in slow synaptic transmission?

Answer 20

The receptor isn’t the ion channel.
It signals to the channel either within the membrane via a G protein, or intracellularly using a G protein which then activates an enzyme that releases a messenger and activates the channel.