S6) The Resting Membrane Potential Flashcards

1
Q

What is membrane potential?

A
  • Membrane potential is the electrical potential difference across their plasma membrane of a cell
  • It is expressed as a voltage of the inside of the cell relative to the outside
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2
Q

How does one measure membrane potential?

A

A microelectrode (fine micropipette) penetrates the cell membranes and can be used to measure membrane potentials

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3
Q

How are membrane potentials established?

A

Membrane potentials are established because the membrane is selectively permeable to different ions due to the presence/absence of channel proteins; membrane-spanning transport proteins that allow ions to permeate

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4
Q

In terms of ion channels, differentiate between gating and selectivity

A
  • Selectivity: the protein channel lets through only one/a few ion types

- Gating: the channel can be open/closed by a conformational change in the protein molecule

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5
Q

Depending on which types of channels are open, the resting membrane can be selectively permeable to certain ion types.

Which ions are involved?

A
  • Na+
  • K+
  • Cl-
  • Ca2+
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6
Q

Outline the 6 steps involved in setting up the resting potential

A

⇒ Membrane is selectively permeable to K+ at rest (open K+ channel)

K+ diffuse out of the cell (down [K+] gradient)

Anions cannot follow

⇒ Cell interior becomes negatively charged

⇒ Newly-created membrane potential opposes outward movement of K+

⇒ System reaches equilibrium

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7
Q

What is potassium equilibrium potential?

A
  • Potassium equilibrium potential (Ek) is the membrane potential when the system reaches equilibrium and there is no net movement of K+
  • This can be calculated from the Nernst equation
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8
Q

Explain the relationship between Ek and resting membrane potential

A
  • Open K+ channels dominate the resting permeability of many cells, so the resting membrane potential is close to the Ek
  • The membrane is not perfectly selective so the RMP is less negative than Ek
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9
Q

What is significant about the relationship between Ek and membrane potential?

A

The dependance of resting membrane potential on K+ permeability means that changing EK with change the RMP

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