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Physiology And Pharmacology > Membrane Potential > Flashcards

Membrane Potential Flashcards

1
Q

What is membrane potential?

A

Magnitude of an electrical charge that exists across a membrane and is always expressed as the potential inside the cell relative to the extracellular solution

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2
Q

What is membrane potential measured in?

A

mV (millivolts)

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3
Q

What is a humans membrane potential at rest?

A

-70mV

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4
Q

What do all animal cells have in common?

A

All animals have negative membrane potentials at rest

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5
Q

What does the electrical potential difference across a plasma membrane provide?

A

The basis of signalling in all types of cells

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6
Q

How can a membrane potential be measured?

A

Microelectrode (fine glass pipette) penetrates cell membrane and uses voltmeter to measure resting potential

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7
Q

What factors are important in the establishment of a membrane potential?

A

Asymmetric distribution of ions across the plasma membrane (concentration gradients)
Selective ion channels in plasma membrane (K+, Na+, Cl- are most important)

In english- concentration gradients and ion channels

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8
Q

Other than ions, what else effects the negative charge in a cell?

A

Proteins (increases negativity as more in cell than outside cell)

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9
Q

What happens if we have a non permeable membrane and no membrane proteins?

A

No movement of ions

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10
Q

What happens if we have a freely permeable membrane?

A

no charge on the membrane but movement of ions

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11
Q

What happens if we have a semi-permeable membrane?

A

charge seperation and an electrical gradient

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12
Q

If electrical and chemical gradients are equal for K+ what happens?

A

No net movement but is a negative charge across the membrane

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13
Q

What is the Nernst equation?

A

Allows you to calculate the membrane potential at which an ion will be in equilibrium, given the extracellular and intracellular concentrations

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14
Q

What does the charge of a cell depend on?

A

The abundance of different channels - if more Na or Ca will have smaller difference as -70mV rather than Cl and K with -95mV

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15
Q

What ion dominates the resting membrane permeability?

A

K+

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16
Q

What cells are close to Ek?

A

Nerve cells and Cardiac cells as many k channels

17
Q

What cells have low resting membrane potentials as have less K channels?

A

Erythrocytes and smooth muscle cells

18
Q

Why are skeletal muscles resting potential so high?

A

lots of Cl- and and K+ channels

19
Q

What is depolarisation?

A

A decrease in size of the membrane potential from its normal value
Cell interior becomes less negative
-70 to -50mV

20
Q

What is Hyperpolarisation?

A

An increase in the size of the membrane potential from it normal value
Cell interior becomes more negative
-70mV to -90mV

21
Q

What does opening K+ or Cl- channels do?

A

Cause hyperpolarisation

22
Q

What does opening Na or Ca channels do?

A

Cause depolarisation

23
Q

What is conductance?

A

The contribution of each ion to the membrane potential will depend on how permeable the membrane is to that ion

24
Q

How are Nicotinic acetyl choline receptors opened?

A

By binding of 2 ACh

25
Q

What are the different types of gating?

A

Ligand- open and close in response to a chemical ligand
Voltage- open and close in response to changes in membrane potential
Mechanical- open and close in response to membrane deformation

26
Q

What is an example of mechanical gating?

A

Hair cells in the inner ear

27
Q

Where do synaptic connection occur?

A

Between nerve cell- nerve, muscle and gland cell

Sensory cell- nerve cells

28
Q

What is a fast synaptic transmission?

A

receptor protein is also an ion channel and causes to open

29
Q

What do excitatory transmitters open?

A

ligand gated channels that cause membrane depolarisation- permeable to Na and Ca

30
Q

What is a Excitatory post-synaptic potential?

A

Longer time course than an action potential
Graded with amount of transmitter
e.g. Aceylcholine Gluamate, Dopamine

31
Q

What do inhibitory transmitters open?

A

ligand gated channels that cause membrane hyperpolarisation- permeable to K or Cl
transmitters- GABA, Glycine, Gamma-aminobutyric acid

32
Q

What is direct G-protein gating?

A

Localised and quite rapid

33
Q

What is gating via an intracellular messenger?

A

Throughout the cell with amplification by cascade

34
Q

What can influence membrane potential?

A

Changes in ion concentration and electrogenic pumps

35
Q

What are the properties of the cardiac ion channel?

A

Selectivity
Voltage sensitive gating- specific MP range for channels to be open
Time dependence- close a fraction of a second after opening again

Physiology And Pharmacology (8 decks)

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