M&R S3 - The Resting Membrane Potential Flashcards Preview

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Flashcards in M&R S3 - The Resting Membrane Potential Deck (20):
1

Can a membrane potential be found in all types of cells?

Yup

2

What is the resting membrane potential?

The potential inside the cell relative to the outside

3

Describe the range of resting membrane potentials seen in animal cells

Animal cells have membrane potentials from -20mV to -90mV

Nerve cells = -50 to -75mV

Smooth muscle cells = -50mV

Cardiac and skeletal muscle = -80 to -90mV

4

How can membrane potential be measured?

A micro-electrode:

Fine glass pipette

Penetrates into the cell

Filled with conducting solution (KCL)

Tip diameter is 1um

Another electrode is placed in the surrounding fluid and a voltmeter used to identify difference in potential across the membrane

5

How is the membrane potential created and controlled?

Selective permeability of membrane to ions through utilisation of transport and channel proteins

These proteins can be gated to allow control of the ion levels intracellularly

See Session 2 for more detail

6

What is the intra and extra-cellular concentration of: Na+ K+ Cl- Other Anions

Na+:

Intra- 10mM

Extra - 145mM

K+:

Intra - 160mM

Extra- 4.5mM

Cl-:

Intra - 3mM

Extra - 114mM

A- (Other Anions):

Intra - 167mM

Extra - 40mM

7

How is the resting membrane potential created?

At rest the membrane has open K+ channels,

K+ diffuses out As Anions cannot follow, the cell becomes negatively charged

The movement of K+ ions out of the cell is opposed by the electrical gradient (they are moving up the gradient).

When electrical and chemical gradients exert the same force on K+ ions the resting potential has been reached

8

Define 'Equilibrium potential' in terms of ions

The membrane potential at which there is no net movement of that ion across the membrane

Concentration gradient = Electrical gradient

9

What is the Nernst equation?

Hint: Assume 37 degrees celsius 

Ions in = concentration of ions inside the cell

Ions out = Concentration of ions outside the cell

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10

Give a brief description of membrane depolarisation

Provide an example of how this might come about

Membrane potential decreases in size towards 0

May only be by a few millivolts, not necessarily an action potential

Cell interior becomes less negative

This could come about by the opening of Na+ or Ca2+ channels

 

11

Give a brief description of membrane hyperpolarisation

Provide an example of how this may come about

Membrane potential increases in size

Potential falls below resting

Cell interior becomes more negative

This could come about by the opening of K+ or Cl- channels

12

Which type of channel dominates the resting permeability of a cell?

Why is the resting potential not equal to the equilibrium potential for this ion?

K+ channels are predominantly open at rest

Resting potential is higher than equilibrium potential -70mV vs -95mV)

Tjis is because other types of channel are also open

13

What effect will changing the equilibrium potential of K+ ions have on a cells resting potential?

Why?

Will change the resting potential in the same direction as the change in equilibrium potential for K+

Resting potential is predominantely influenced by K+ permeability/equilibrium potential

14

Explain what is calculated by the Goldman-Hodgkin-Katz equation

Write out the equation, explain the meaning of any symbols present

The GHK equation provides a good approximation of membrane potential as determined by Na+, K+ and Cl- ions

 

Vm = Membrane potential

PNa P PCl  = Relative permeabilities of the ions

[ion] = concentration of the ion

R = Gas constant

T = Temperature (celsius)

F = Faraday's number

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15

What are the two types of channel gating?

Give a brief description of each type

Ligand Gating:

Channel is opened or closed by binding of a chemical ligand which may be an intra or extra cellular messenger

Voltage Gating:

The channel opens or closes in response to changes in the membrane potential

16

Where types of cells are synaptic connections found between?

What are the two types of synaptic transmission?

Synaptic transmission occurs between nerve, muscle, sensory cells and glands

Fast and slow synaptic transmission

17

What is the distinction between fast and slow synaptic transmission?

Fast:

The receptor proteins is also an ion channel, the binding of neurotransmitter causes the channel to open

Slow:

The receptor protein and ion channel are separate proteins.

18

What is are the patterns of slow synaptic transmission?

Provide a brief explanation of each

Direct G-protein gating:

Receptor is directly linked to the ion channel by G protein

This process is localised and quite rapid

 

Gating via intracellular messenger:

G-protein linked receptor activates an enzyme, iniatiating a signalling cascade resulting in the opening of the ion channel

This activation occurs throughout the cell

19

Describe the action of Excitatory synapses

Hint: Channels, Potential change

Excitatory transmitters open ligand gated channels, this causes membrane depolarisation

Transmitters include Acetylcholine, Glutamate

Graded with the amount of transmitter

Can be permeable to Na+, Ca2+ or cations in general

Results in an Excitatory Post Synaptic Potential (EPSP)

Has a longer time course than an action potential

20

Describe the action of inhibitory synapses

Hint: Channels, Potential change

Inhibitory transmitters open ligand gated channels, this causes membrane hyperpolarisation

Transmitters include Glycine, GABA

Graded with the amount of transmitter

Permeable to K+ or Cl-

Results in an Inhibitory Post Synaptic Potential (IPSP)

Has a longer time course than an action potential