Session 4

Question 1

What is a membrane potential

Answer 1

electrical charge that exists across a membrane

Question 2

Animal cells negative membrane potential range

Answer 2

-20 to -90 mv

Question 3

Cardiac and skeletal muscle cells resting potentials

Answer 3

-80 to -90

Question 4

Nerve cells resting potentials

Answer 4

-50 to -75

Question 5

How do you measure membrane potential

Answer 5

Microelectrode can penetrate cell membrane

Question 6

Smooth muscle myocytes resting membrane potential

Answer 6

-50

Question 7

Skeletal muscle myocytes resting membrane potential

Answer 7

-90

Question 8

Neurones resting membrane potential -

Answer 8

-70

Question 9

Cardiac myocytes resting membrane potential

Answer 9

-80

Question 10

How does selective permeability arise

Answer 10

Phospholipid bilayer

Ion channels -Channel properties

Question 11

Explain selective permeability of lipid bilayer

Answer 11

Hydrophobic interior, permeable to small uncharged molecules

Question 12

What are ion channels

Answer 12

Proteins that enable ions to cross cell membranes, have an aqueous pore through which ions flow by diffusion

Question 13

How do you set up the membrane resting potential

Answer 13

Open K+ channels dominate, equal and opposite so no net movement of K+ hence negative membrane potential

Membrane is selectively permeable to K+

Question 14

What is equilibrium potential

Answer 14

Membrane potential at which something will be in equilibrium

Question 15

Nernst equation

Answer 15

61 log10 concentration outside/inside

Question 16

Characteristic of cells with lower resting potential

Answer 16

Lower selectivity for K+ due to increased contribution from other channels

Question 17

Cardiac muscle and nerve cell characteristics

Answer 17

Resting potential close to Ek

Question 18

Depolarization

Answer 18

Decrease in the size of the membrane potential, cell interior becomes less negative

Question 19

Hyperpolarization

Answer 19

Increase in the size of the membrane potential, cell interior becomes more negative

Question 20

What causes hyperpolarization

Answer 20

opening K+ or Cl- channels

Question 21

What causes depolarization

Answer 21

Opening of Na+ or Ca+ channels

Question 22

Changes in membrane potential are caused by

Answer 22

Changes in activity of ion channels

Question 23

Example of a less selective channel

Answer 23

Neuromuscular junction, nicotinic acetylcholine receptors can be activated by ACh or nicotine

Question 24

Nicotinic Acetylcholine Receptors mechanism

Answer 24

Intrinsic ion channel
Open by binding of acetylcholine
Let’s Na+ and K+ through
Membrane potential towards 0mv (intermediate between ENa and EK)

Question 25

3 types of gating

Answer 25

Ligand gating, Voltage gating, Mechanical gating (membrane deformation e.g. mechanoreceptors)

Question 26

Fast synaptic transmission

Answer 26

Receptor protein also ion channel

Question 27

What do excitatory transmitters do

Answer 27

Open ligand gated channels that cause membrane depolarisation (Na+ and Ca2+)

E.g. acetylcholine, glutamate (longer time course than AP)

Question 28

What do inhibitory transmitters do

Answer 28

Open ligand gated channels that cause hyperpolarisation (K+ and Cl-)

E.g. glycine, GABA

Question 29

Features of slow synaptic transmission

Answer 29

Receptor and Channel are separate proteins

Direct G protein gating, or gating via an intracellular messenger

Question 30

Other factors that influence membrane potential

Answer 30

Changes in ion concentration, Electrogenic pumps,