*Physiology 2 (lecture 4) Flashcards

1
Q

What is the membrane potential? (Em)

Units?

A

Separation of opposite charges across the membrane

mV (the membrane itself is not charged)

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2
Q

In terms of membrane potentials, what do excitable cells (e.g. nerve and muscle) have the ability to do?

A

Produce rapid, transient changes in their membrane potential when excited e.g. action potentials

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3
Q

What is the is the resting membrane potential?

A

Constant in non-excitable cells and in excitable cells at rest

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4
Q

What is the membrane potential due to?

A

Difference in the concentration and permeability of key ions

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5
Q

Extracellular and intracellular concentration of Na+?

Concentration gradient

A

E = 150
I = 15
Inward

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6
Q

Extracellular and intracellular concentration of K+?

Concentration outward?

A

E = 5
I = 150
Outward

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7
Q

Relative permeability of sodium and potassium?

A
Na+ = 1
K+ = 100
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8
Q

Is the plasma membrane permeable to the large relatively negatively charged (anionic) intracellular proteins?

A

No - it is impermeable to these

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9
Q

Is the inside or outside of the cell more negatively charged?

A

Inside

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10
Q

Is the electrical gradient for K+ inwards or outwards?

Is the concentration gradient for K+ inwards or outwards?

A

Inwards

Outwards

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11
Q

What is the equilibrium point?

A

The point where there is no net movement of charge (when the concentration gradient and electrical gradient balance each other out)

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12
Q

What is the equilibrium point for K+?

A

-90 mV

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13
Q

What does the negative sign before the equilibrium potential for K+ mean?

A

The polarity of the excess charge is on the inside of the membrane

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14
Q

What can be calculated using the Nernst equation?

A

The equilibrium potential for any given ion

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15
Q

What is the Nerst equation for a monovalent ion at 37 degrees?

A

Eion = 61log10([ion]o/[ion]i)

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16
Q

Direction of electrical and concentration gradient for Na+?

A

Both inwards

17
Q

What is the equilibrium potential for Na+?

A

+60mV

18
Q

What effect does permeability for a given ion have on its tendency to drive membrane potential towards its own equilibrium potential?

A

The greater the permeability for a given ion, the greater the tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential

19
Q

What effect does concurrent K+ and Na+ movement have on establishing the resting Em?
Resting membrane potential

A

Relatively large net diffusion of K+ outward (higher permeability)
Relatively small net diffusion of Na+ inward neutralised some of the potential created by K+ alone
Resting membrane potential therefore = -70mV

20
Q

What can be used to calculate Em?

A

The Goldman-Hodgkin-Katz equation

21
Q

What is the Goldman-Hodgkin-Katz equation?

A

Em=61log10((PK+[K+]0 + PNa+[Na+]0) / (PK+[K+]i + PNa+[Na+]i))

22
Q

What does hyper polarisation mean?

A

a change in a cell’s membrane potential that makes it more negative

23
Q

What type of current does the Na+K+ATPase pump generate?

A

A hyper polarising current

24
Q

What does depolarisation mean?

A

Making it more positive

25
Q

What does repolarisation men?

A

the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential has changed the membrane potential to a positive value