M&R 3.1 - Resting Membrane Potential and Changing Membrane Potential

Question 1

What is the resting potential range for animal cells?

Answer 1

-20mV to -90mV

Question 2

What is the resting potential range for nerve cells?

Answer 2

-50mV to -75mV

Question 3

What is the resting potential range for smooth muscle cells?

Answer 3

Around -50mV

Question 4

What is the resting potential range for cardiac and skeletal muscle cells?

Answer 4

-80mV to -90mV

Question 5

At rest, which ion dominates permeability?

Answer 5

K+

• More inside the cell than out so moves out of cell

Question 6

How does the domination of K+ create a potential?

Answer 6

• Open K+ channels dominate membrane ionic permeability at rest
• No net movement of K+ but there is a negative membrane potential
• Creates an electrical gradient which draws K+ back in

Question 7

What is the Nernst equation used for?

Answer 7

The application of the balance between electrical and chemical gradients to give the membrane potential at which the specific ion will be in equilibrium

Question 8

How do voltage gated ion channels indirectly affect the membrane potential?

Answer 8

• Have spontaneous opening and closing
• Leakage of Na+ or K+ into the cell makes the membrane less negative
• Leakage of Cl- into the cell makes the membrane more negative

Question 9

Why is the resting potential of nerve cells and cardiac muscle not exactly Ek?

Answer 9

It’s slightly less negative due to the membrane not being perfectly selective for K+

Question 10

Describe the selectivity of smooth muscle for K+

Answer 10

Lower due to higher contribution from other channels which results in a more positive resting potential

Question 11

Why is the resting potential of skeletal muscle close to both Ek and Ecl?

Answer 11

Both Cl- and K+ channels are open

Question 12

What does a change in permeability of a membrane do to the membrane potential?

Answer 12

Membrane potential moves closer to Ep for the specific ion

Question 13

What is the definition of depolarisation?

Answer 13

The DECREASE in size of the membrane potential from its normal value therefore causing the inside of the cell to become LESS negative

Question 14

What is the definition of hyperpolarisation?

Answer 14

The INCREASE in size of the membrane potential from its normal therefore causing the inside of the cell to become MORE negative

Question 15

Give an example of a less selective ion channel. How does it work?

Answer 15

• Nicotinic acetylcholine receptor at the neuromuscular junction
• Ach binds which causes the channel to open
• Influx of Na+ and K+
• Moves membrane potential to around 0mV which is between Ena and Ek

Question 16

Name the three types of gating

Answer 16

• Ligand e.g. Synapses
• Voltage (respond to a change in membrane potential)
• Mechanial e.g. Stretch receptors

Question 17

What are the two types of synapse?

Answer 17

• Fast (excitatory and inhibitory)

- Slow

Question 18

Describe a fast synapse

Answer 18

The receptor proteins is also an ion channel

Question 19

What is an excitatory post synaptic potential?

Answer 19

• A depolarisation of the membrane due to the positive Ep that increases the chance of generating an action potential on the PSM
• Longer and graded in size depending on the transmitter
• Fast and slow responses

Question 20

What is an inhibitory post synaptic potential?

Answer 20

• A hyperpolarisation of the membrane due to a negative Ep

Question 21

Describe a slow synapse

Answer 21

Receptor and channel are separate proteins

Question 22

Describe how G proteins are used in slow synapses

Answer 22

• G protein is released upon binding of the ligand
• Binds to effector (usually the channel)
• Localised and quite rapid

Question 23

Describe how intracellular messengers are used in slow synapses

Answer 23

• Bind to an enzyme

- Enzyme converts substrate into a signalling molecule

Question 24

What are the other two influential factors of membrane potentials?

Answer 24

• Ion concentration

- Electrogenic pumps

Question 25

What is the definition of resting membrane potential?

Answer 25

The potential inside the cell relative to the outside when at rest