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Flashcards in Membranes and cell excitation Deck (44):
1

An electrical signal involves...

...a change in the balance of positive and negative charges

2

Name 5 important charged particles

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

3

What controls ion movement inside and outside of a cell?

The membrane

4

What generates an electrical signal?

The transfer of ions through ion channels

5

What maintains gradients?

Ion pumps

6

Describe lipid bilayer permeability

Impermeable to most molecules, including ions

7

The inside of a cell contains...

....an excess of anions

8

What is the voltage inside the cell called?

Membrane potential (Em)

9

What is the membrane potential of a neurone?

-65mV

10

What determines membrane potential?

The balance of charges

11

Ion movement is...

...passive

12

Which ion channels are permeant?

Na+, K+, Ca2+, Cl-

13

Why are membrane proteins essential?

They control membrane potential

14

Name the three types of gated channels

Non-gated, voltage, ligand

15

What are non-gated channels also known as?

Leak channels

16

What do voltage-gated channels do?

Generate action potentials

17

What do ligand-gated channels do?

Generate membrane potential changes at synapses

18

Neurones are _____ cells

Excitable cells

19

Neurones have a resting membrane potential of...

...-60mV to -70mV

20

What factors influence ion movement across the cell membrane?

Unequal ion distribution and electrical force

21

What does the permeability of the membrane tell us?

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

22

What do efflux and influx mean?

Efflux = movement out
Influx = movement in

23

Define equilibrium

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

24

What is equilibrium potential abbreviated to?

Eion

25

What does the Nernst equation do?

Defines the voltage at which the ion is at equilibrium

26

What is happening at equilibrium potential?

The amount of efflux = influx

27

What is different between Eion and Em

Eion is a constant, Em can vary

28

What is ionic driving force?

Em - Eion

29

Explain ionic driving force

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

30

Is ionic driving force proportional?

Yes

31

In a neurone, what influences Em?

Na+ and K+

32

Em rests between what?

EK and ENa

33

How do we calculate Em?

The Goldman equation

34

What is Em dependent on?

Relative permeabilities (Pion)

35

Compare the relative permeabilities of Na and K

PK is 40x bigger than PNa

36

Why is Em closer to EK?

Because of the difference in permeabilities

37

What is happening at -65mV in a neurone?

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

38

What is making Na+ move in?

Chemical gradient and electrical force

39

What is making K+ move out?

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

40

What ensures Em of -65mV is at rest?

Na+ influx = K+ efflux

41

Compare the driving force of Na+ and K+

Na+ = large
K+ = small

42

Compare the permeability to Na+ and K+

Na+ = small
K+ = large

43

Do ion pumps control Em?

No, they maintain concentration in the long term

44

What does the sodium-potassium pump do?

Exchanges internal Na+ for external K+
(against concentration gradient)