3.1 - The Resting Membrane Potential

Question 0

What is the membrane potential of cardiac muscle cells?

Answer 0

-80mV

Question 1

Define membrane potential

Answer 1

The electrical potential difference across the plasma membrane of all cells

Question 2

What is the membrane potential of skeletal muscle cells?

Answer 2

-90mV

Question 3

How do membrane potentials arise?

Answer 3

Different membranes are selectively permeable to different ions as they have different numbers and types of channel proteins

Question 4

What are the three features of ion channels?

Answer 4

Selectivity
Gating
Ions flow rapid if there is an electrochemical gradient

Question 5

Define equilibrium potential

Answer 5

The membrane potential at which the electrical gradient and chemical gradient are equal

Question 6

The equilibrium potential for K+ is -90mV. Why is the resting membrane potential higher than this?

Answer 6

Membrane potential for average cell is -70mV as there is spontaneous flickering of Ca2+ and Na+ channels

Question 7

Why do cardiac muscle and nerve cells have a lower membrane potential?

Answer 7

More selective for K+ but not quite -95mV as the membrane is not perfectly selective for K+

Question 8

Why may cells have a less negative resting membrane potential?

Answer 8

Deceased selectivity for K+

Increased contribution from other channels

Question 9

Define depolarisation

Answer 9

A decrease in membrane potential from its normal value

Question 10

Define hyperpolarisation

Answer 10

An increase in membrane potential from its normal value

Question 11

What effect does changing the membrane permeability of an ion have on the membrane potential?

Answer 11

Increased permeability of an ion will move the membrane potential closer to the equilibrium potential of that ion

Question 12

What are the three types of gating of ion channels?

Answer 12

Ligand
Voltage
Mechanical

Question 13

Describe how ligand gated channels work

Answer 13

The channel opens/closes in response to binding of a chemical ligand

Question 14

Describe how voltage-gated ion channels work

Answer 14

Opens/closes in response to changes in membrane potential

Question 15

Describe how mechanical-gated ion channels work

Answer 15

Open/close in response to membrane deformation

Question 16

Describe synaptic transmission

Answer 16

A chemical transmitter is released from the presynaptic membrane
Travels across the synaptic cleft and binds to receptors on the post synaptic membrane

Question 17

Describe fast synaptic transmission

Answer 17

Neurotransmitter directly causes the ion channel to open as the receptor protein is also an ion channel

Question 18

Describe slow synaptic transmission

Answer 18

The receptor and ion channel are separate so it takes longer for the transmitter to have an effect

Question 19

Slow synaptic transmission involves G-Proteins. What are the two ways in which proteins can work?

Answer 19

• the G-protein directly causes the ion channel to open
• the G-protein activates a signalling cascade that leads to the production of an intracellular messenger or protein kinase that causes the channel to open

Question 20

What are the two types of synapses?

Answer 20

• excitatory synapses that cause membrane depolarisation

- inhibitory synapses that cause membrane hyperpolarisation

Question 21

What factors influence membrane potential?

Answer 21

• changes in ion concentration, particularly K+

- Electrogenic pumps