Membranes and cell excitation

Question 1

An electrical signal involves…

Answer 1

…a change in the balance of positive and negative charges

Question 2

Name 5 important charged particles

Answer 2

Na+, K+, Cl-, Ca2+ and protein side chains

Question 3

What controls ion movement inside and outside of a cell?

Answer 3

The membrane

Question 4

What generates an electrical signal?

Answer 4

The transfer of ions through ion channels

Question 5

What maintains gradients?

Answer 5

Ion pumps

Question 6

Describe lipid bilayer permeability

Answer 6

Impermeable to most molecules, including ions

Question 7

The inside of a cell contains…

Answer 7

….an excess of anions

Question 8

What is the voltage inside the cell called?

Answer 8

Membrane potential (Em)

Question 9

What is the membrane potential of a neurone?

Answer 9

-65mV

Question 10

What determines membrane potential?

Answer 10

The balance of charges

Question 11

Ion movement is…

Answer 11

…passive

Question 12

Which ion channels are permeant?

Answer 12

Na+, K+, Ca2+, Cl-

Question 13

Why are membrane proteins essential?

Answer 13

They control membrane potential

Question 14

Name the three types of gated channels

Answer 14

Non-gated, voltage, ligand

Question 15

What are non-gated channels also known as?

Answer 15

Leak channels

Question 16

What do voltage-gated channels do?

Answer 16

Generate action potentials

Question 17

What do ligand-gated channels do?

Answer 17

Generate membrane potential changes at synapses

Question 18

Neurones are _____ cells

Answer 18

Excitable cells

Question 19

Neurones have a resting membrane potential of…

Answer 19

…-60mV to -70mV

Question 20

What factors influence ion movement across the cell membrane?

Answer 20

Unequal ion distribution and electrical force

Question 21

What does the permeability of the membrane tell us?

Answer 21

How easily an ion moves across the membrane (via ion channels)

Question 22

What do efflux and influx mean?

Answer 22

Efflux = movement out
Influx = movement in

Question 23

Define equilibrium

Answer 23

An ion is in equilibrium when chemical gradient and electrical force are in balance

Question 24

What is equilibrium potential abbreviated to?

Answer 24

Eion

Question 25

What does the Nernst equation do?

Answer 25

Defines the voltage at which the ion is at equilibrium

Question 26

What is happening at equilibrium potential?

Answer 26

The amount of efflux = influx

Question 27

What is different between Eion and Em

Answer 27

Eion is a constant, Em can vary

Question 28

What is ionic driving force?

Answer 28

Em - Eion

Question 29

Explain ionic driving force

Answer 29

What drives the ion across the membrane when Em is not equal to Eion

Question 30

Is ionic driving force proportional?

Answer 30

Yes

Question 31

In a neurone, what influences Em?

Answer 31

Na+ and K+

Question 32

Em rests between what?

Answer 32

EK and ENa

Question 33

How do we calculate Em?

Answer 33

The Goldman equation

Question 34

What is Em dependent on?

Answer 34

Relative permeabilities (Pion)

Question 35

Compare the relative permeabilities of Na and K

Answer 35

PK is 40x bigger than PNa

Question 36

Why is Em closer to EK?

Answer 36

Because of the difference in permeabilities

Question 37

What is happening at -65mV in a neurone?

Answer 37

Driving force acting on both Na+ and K+ Na+ influx K+ efflux

Question 38

What is making Na+ move in?

Answer 38

Chemical gradient and electrical force

Question 39

What is making K+ move out?

Answer 39

Chemical gradient, but electrical force is making K+ move in

Question 40

What ensures Em of -65mV is at rest?

Answer 40

Na+ influx = K+ efflux

Question 41

Compare the driving force of Na+ and K+

Answer 41

``` Na+ = large K+ = small ```

Question 42

Compare the permeability to Na+ and K+

Answer 42

``` Na+ = small K+ = large ```

Question 43

Do ion pumps control Em?

Answer 43

No, they maintain concentration in the long term

Question 44

What does the sodium-potassium pump do?

Answer 44

Exchanges internal Na+ for external K+ | against concentration gradient