The Resting Membrane Potential

Question 1

What do all cells have?

Answer 1

An electrical potential difference (voltage) across their plasma membrane

Question 2

What does the membrane potential provide?

Answer 2

The basis of signalling in the nervous system, as well as in many other types of cells

Question 3

How is the resting membrane potential expressed?

Answer 3

As the potential inside the cell relative to the extracellular solution

Question 4

What is the membrane potential of animal cells?

Answer 4

They have negative membrane potentials, that range from -20 to -90mV

Question 5

What is the resting potential of nerve cells?

Answer 5

-50 to -75mV

Question 6

What is resting membrane potentials of smooth muscle cells?

Answer 6

~ -50mV

Question 7

What is the resting membrane potential of skeletal and cardiac muscle cells?

Answer 7

-80 to -90 mV

Question 8

What is the cell membrane selectively permeable to?

Answer 8

Different ions

Question 9

How does the permeability of the membrane to ions occur?

Answer 9

By way of channel proteins

Question 10

What makes the whole cell membrane selectively permeable to ions?

Answer 10

The selectivity of ion channels and the types of channels that are open

Question 11

What dominates the membrane ionic permeability at rest for most cells?

Answer 11

Open K+ channels

Question 12

When is there no net movement of K+?

Answer 12

When the chemical and electrical gradients for K+ are equal and opposite

Question 13

What is true when there is no net movement of K+?

Answer 13

There will be a negative membrane potential

Question 14

What does the resting membrane potential arise because of?

Answer 14

The membrane being selectively permeable to K+

Question 15

What is the intracellular concentration of Na?

Answer 15

~10mM

Question 16

What is the extracellular concentration of Na?

Answer 16

145mM

Question 17

What is the intracellular concentration of K?

Answer 17

160mM

Question 18

What is the extracellular concentration of K?

Answer 18

4.5mM

Question 19

What is the intracellular concentration of Cl?

Answer 19

4mM

Question 20

What is the extracellular concentration of Cl?

Answer 20

114mM

Question 21

What is the intracellular concentration of anions (other can Cl)?

Answer 21

167mM

Question 22

What is the extracellular concentration of anions (other than Cl)

Answer 22

40mM

Question 23

What anions other than Cl are involved in the gradient across the cell membrane?

Answer 23

Phosphate
Bicarbonate
Amino acids
Charged groups on proteins

Question 24

In what direction is the K concentration gradient?

Answer 24

From the inside of the cell to the outside of the cell

Question 25

In what direction is the K electrical gradient?

Answer 25

From the outside of the cell to the inside of the cell

Question 26

What is the equilibrium potential for an ion?

Answer 26

The membrane potential at which there is no net movement of the ion across the membrane (the concentration gradient = the electrical gradient)

Question 27

What can be used to calculate the equilibrium potential?

Answer 27

The Nernst Equation

Question 28

What happens in depolarisation?

Answer 28

Membrane potential decreases in size

Question 29

Does depolarisation cause an action potential?

Answer 29

Not necessarily- it may only be a few mV

Question 30

What happens to the cell interior in depolarisation?

Answer 30

It becomes less negative

Question 31

What causes depolarisation?

Answer 31

Opening of Na or Ca channels

Question 32

What happens in hyperpolarisation?

Answer 32

The membrane potential increases in size, falling below resting

Question 33

What happens to the cell interior in hyperpolarisation?

Answer 33

It becomes more negative

Question 34

What causes hyperpolarisation?

Answer 34

Cl or K channels opening

Question 35

What do cells have in reality?

Answer 35

Channels open for more than one type of ion

Question 36

What does the contribution of each ion to the membrane potential depend on?

Answer 36

How permeable the membrane is to that ion

Question 37

What can change a cells membrane potential?

Answer 37

Changes in the cells permeability to a single ion

Question 38

How can be used to cells membrane potential be calculated?

Answer 38

The GHK equation

Question 39

What does the GHK equation show?

Answer 39

That membrane potential depends on the number of open channels open for each ion

Question 40

Where can synaptic connections occur?

Answer 40

Between nerve, muscle, sensory cells and glands

Question 41

How can synaptic transmission be categorised?

Answer 41

Into fast and slow

Question 42

What is the receptor protein in fast synaptic transmission?

Answer 42

A ion chanel

Question 43

What happens in fast synaptic transmission?

Answer 43

The binding of transmitter causes the channel to open

Question 44

What happens in slow synaptic transmission?

Answer 44

The receptor protein and ion channel are separate proteins, that may be linked by G-proteins or intracellular messengers

Question 45

What are the two basic patterns of slow synaptic transmission?

Answer 45

Direct G-protein gating  | Gating via an intracellular messenger

Question 46

What are the characteristics of direct G-protein gating?

Answer 46

Localised | Quite rapid

Question 47

How does gating via an intracellular messenger work?

Answer 47

The G-protein activates an enzyme, which initiates a signalling cascade, through an intracellular messenger or protein kinase which activates the channel

Question 48

What are the characteristics of gating via an intracellular messenger?

Answer 48

Occurs throughout the cell  | Amplification by cascade

Question 49

What do excitatory transmitters do?

Answer 49

Open ligand-gated channels, causing membrane depolarisations

Question 50

What can ligand-gated channels opened by excitatory transmitters be permeable to?

Answer 50

Na, Ca, and sometimes cations in general

Question 51

What is the membrane depolarisation caused by excitatory transmitters called?

Answer 51

Excitatory Post-Synaptic Potential (EPSP)

Question 52

How does EPSP differ from an AP?

Answer 52

It is graded with the amount of transmitter

Question 53

Give two examples of excitatory transmitters

Answer 53

Acetylcholine | Glutamate

Question 54

What do inhibitory transmitters do?

Answer 54

Open ligand-gated channels, causing hyperpolarisation

Question 55

What are ligand-gated channels opened by inhibitory transmitters permeable to?

Answer 55

K or Cl

Question 56

What is the hyperpolarisation caused by inhibitory transmitters called?

Answer 56

Inhibitory post-synaptic potential (IPSP)

Question 57

Give 2 examples of inhibitory transmitters

Answer 57

Glycine | γ-aminobutyric acid (GABA)