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ICPP > Lecture 7 - Resting Membrane Potential > Flashcards

Lecture 7 - Resting Membrane Potential Flashcards

1
Q

What is meant by selective permeability?

A

Certain ions channels in a cells membrane are open at a particular time allowing movement of these ions into or out of the cell

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2
Q

What cells have a membrane potential?

A

All cells have a membrane potential

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3
Q

What is a membrane potential of a cell?

A

The electrical potential difference (difference in electrical charge) across the cells plasma membrane

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4
Q

What is membrane potential important for?

A

Cell to cell signalling
Providing IMMEDIATE energy source for ion transport (electrochemical gradient)

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5
Q

What is used to measure the membrane potential of a cell?

A

Microelectrode
Conducting solution

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6
Q

How is the membrane potential of a cell measured?

A

The fine glass pipette of one side of the microelectrode penetrates the cell membrane into the cell (without disrupting membrane structure)
Cell filled with conducting solution

Other part of the electrode remains extracellular and gets zeroed

Membrane potential then measured

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7
Q

What does the value of membrane potential actually mean? For example if membrane potential was measured as -90mV what does this actually mean?

A

The difference in charge of the inside of the cell compared to the outside

-90mV means that the inside of the cell is 90mV MORE NEGATIVELY charged than the outside of the cell

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8
Q

What is 1mV in Volts?

A

1mV = 0.001V
1mV = 10^-3 V

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9
Q

What is Resting Membrane Potential?

A

The electrical potential (charge) difference across the plasma membrane of the cell when the cell is not stimulated/excited

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10
Q

What does RMP stand for?

A

Resting Membrane Potential

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11
Q

What is the RMP of Cardiac ventricular myocytes and Atrial myocytes?

A

-85mV

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12
Q

What is the RMP of Neurones?

A

-70mV

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13
Q

What is the RMP of Skeletal muscle myocytes?

A

-90mV

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14
Q

What is the RMP of Smooth muscle myocytes?

A

-50mV

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15
Q

What is an excitable cell?

A

Cell that can fire action potentials

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16
Q

What is a non excitable cell?

A

Cell that can NOT fire action potentials

17
Q

What is the normal range of resting membrane potentials for cells?

A

-10mV to - 100mV

18
Q

Which cells in the body do not have a resting membrane potential?

A

Pacemaker cells (SAN cells)
Depolarise — Repolarise — Immediately depolarise — etc..

19
Q

How does depolarisation occur in non excitable cells? (Vascular smooth muscle)

A

Graded potentials
Gradually changes
Occurs as a repsonse to stimuli

20
Q

What happens to vascular smooth muscles as it gradually depolarises?

A

Muscle contraction
Vasoconstriction

21
Q

What happens when hyperpolarisation happens in vascular smooth muscle cells?

A

Muscle relaxes and dilates
Vasodilation

22
Q

What do ions require in order to cross the cell membrane?

A

Ion channels

23
Q

What is the key feature of an ion channel that allows ions to flow through?

A

Aqueous hydrophilic pore

24
Q

What are the 3 properties of channels?

A

Selectivity
Gating
Rapid ion flow (Always down ELECTROCHEMICAL GRADIENT)

25
Q

What are the 3 main factors/ concepts that determine RMP of a cell?

A

Selective permeability to ions at rest

Relationship between electrochemical gradients and equilibrium potentials

Contribution of Na+/K+ ATPase

26
Q

What is the main contributor (Ion channel) to resting membrane potential?

A

The leaky K+ channel

27
Q

How does the leaky potassium ion channel play the main role in setting up resting membrane potential?

A

Membrane selectively permeable to K+ so K+ moves out of cell down Concentration gradient through leaky K+ channels

Anions cant follow out of the cell since the membrane is not selectively permeable to them

Internal environment more negative

Negative charge inside of cell eventually equally pulls on K+ trying to draw it back into cell with an equal force that the concentration gradient of K+ has on forcing K+ out of cell

No net movement of K+
Potassium equilibrium potential reached

28
Q

What is meant by the equilibrium potential for an ion?

A

Its the potential difference for that ion at which the chemical gradient and electrical gradient are both equal and opposite

The draw from the electrical gradient into the cell matches the force of the ion moving out of the cell down its chemical concentration gradient

29
Q

What is the net movement of K+ when the cell is at the Equilibirum potential for K+ (Ek)?

A

No overall net movement

30
Q

What is the Nernst equation used to calculate?

A

The membrane potential at which an ion will be in equilibrium

31
Q

What is the Intracellular concentration of Na+, K+, Cl- and Anion like compared to outside the cell?

A

Na+ = LOW in cell
K+ = HIGH in cell
Cl- = LOW in cell
Anions = HIGH in cell

32
Q

Why are cells Resting Membrane potential not equal to the Equilibrium potential for potassium (Ek)?

A

Membrane not perfectly selectively permeable to K+. Other ions can leak across the membrane like Na+ and Ca2+. This makes the cell slightly more positive than Ek

33
Q

What would the RMP of a cell that is PERFECTLY selectively permeable to Na+ if the E(Na) is +60mV?

A

+60mV

34
Q

What affect does a cell becoming more selectively permeable to an ion have on the cells RMP?

A

Gets closer to the equilibrium potential for that cell

35
Q

What conditions do unsynchronised action potentials (Delayed after depolarisations) cause to the heart?

A

Cardiac arrhythmias

36
Q

What is the meaning of the equilibrium potential of an ion?

A

The concentration gradient of the ion movement of the cell is equal to the electronical pull of the ion back into the cell

37
Q

What is the role of Na+/K+ ATPase in RMP?

A

Counteracts the inward flow of Na+ through leaky Na+ down the electrochemical gradient by pumping 3Na+ out for each cycle

Maintains the RMP

38
Q

Using either “Major, Secondary or none” as a description, what is the contribution of these channel proteins on RMP?
Leaky K+ Channel
Leaky Na+ Channel
Transporters and exchangers
Na+/K+ ATPase
GLUT 1-4

A

Leaky K+ Channel: Major
Leaky Na+ Channel: Secondary
Transporters and exchangers: Secondary
Na+/K+ ATPase: Secondary
GLUT 1-4: None

ICPP (23 decks)

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