Session 4: Resting Membrane Potential Flashcards Preview

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Flashcards in Session 4: Resting Membrane Potential Deck (28)
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1
Q

What is a membrane potential?

A

The electrical potential difference across the plasma membrane of ALL cells

2
Q

How is the resting potential of a cell measured?

A

Using a very fine glass micropipette called a microelectrode to penetrate the cell membrane
The micropipette is filled with conducting solution

3
Q

What are the range of values for resting potentials of animal cells?

A

-20mV to -90mV

4
Q

The resting membrane potentials are largest in which cells?

A

Skeletal muscle and cardiac muscle (-80mV to -95mV)

5
Q

What is the range of nerve cell resting potential?

A

-50mV to -75mV

6
Q

Explain the concept of selective permeability

A

The resting membrane can be selectively permeable to ions, based on the types of ion channel proteins that are in the membrane and whether gated channels are open or not

7
Q

How does selective permeability of cell membranes arise?

A

Through channel proteins present in the cell membrane which allow some ions to permeate. They are characterised by selectivity, gating and a high rate of ion flow down the electrochemical gradient for the ion

8
Q

How is the resting potential set up given the distribution of ions across cell membrane?

A

At rest, the a typical mammalian cell has open K+ channels, so is selectively permeable to K+. Since anions cannot follow, the cell becomes negatively charged inside with the generation of an electrical gradient

9
Q

What is the “equilibrium potential for an ion”?

A

The electrical and chemical gradients for K+ are equal and balance so there is no net driving force on K+ across the membrane

10
Q

How would you calculate equilibrium potential for an ion from the ionic concentrations on either side of the plasma membrane?

A

Using the Nernst equation

11
Q

What is depolarization?

What happens to the interior of the cell in relation to charge?

A

A decrease in the membrane potential, so that the inside of the cell becomes less negative

12
Q

What is hyperpolarisation?

What happens to the interior of the cell in relation to charge?

A

An increase in the membrane potential, so that that the inside of the cell becomes more positive

13
Q

Explain mechanisms that may lead to depolarisation

A

Opening Na+ or Ca2+ channels

14
Q

Explain the mechanisms hat may lead to hyperpolarisation

A

Opening K+ or Cl- channels

15
Q

Explain how changes in ion activity can lead to changes in the membrane potential

A

c

16
Q

Outline some of the roles of the membrane potential in signalling within and between cells

A

c

17
Q

Outline how ligand-gated channels can give rise to synaptic potentials

A

Synaptic potentials can be fast or slow depending on wether the receptor is also an ion channel, and depending on which ions the channels are selective for

18
Q

What does increasing the membrane permeability for a particular ion do to the membrane potential for that ion?

A

Moves it towards the equilibrium potential

19
Q

How do we deal with real membranes that are not perfectly selective for one ion species?

A

Use the Goldman-Hodgkin-Katz (GHK) equation

20
Q

How do we deal with real membranes that are not perfectly selective for one ion species?

A

Use the Goldman-Hodgkin-Katz (GHK) equation

21
Q

In fast synaptic transmission, the receptor is also what kind of channel?
What does this mean?

A

Ligand-gated ion channel
It has two functions:
1) It binds its related ligand (neurotransmitter)
2) It acts as an ion channel

22
Q

Depolarising transmitters open channels with _______ reversal potentials, i.e. channels selective for what?

A

Na+, Ca2+

23
Q

Do depolarising transmitters lead to excitatory or inhibitor postsynaptic potential?

A

Excitatory postsynaptic potential (EPSP)

24
Q

Hyperpolarizing transmitters open channels with _______ reversal potentials i.e. channels selective for what?

A

K+ or Cl-

25
Q

Do hyperpolarizing transmitters lead to excitatory or inhibitory postsynaptic potential?

A

Inhibitory postsynaptic potential (IPSP)

26
Q

What is the difference between fast and slow synaptic transmission?

A

In fast synaptic transmission, the receptor itself is a ligand-gated ion channel whereas in slow synaptic transmission it is not itself an ion channel, but signals to the channel

27
Q

Which two ways can the receptor in slow synaptic transmission signal to the channel?

A

Within the membrane -localised and rapid

Via an intracellular messenger - throughout the cell, amplified by cascade

28
Q

What two other factors can influence membrane potential, apart from ion channels?

A
Changes in ion concentration 
Electrogenic pumps (e.g.NA/K ATPase)