L10 - resting and action potential Flashcards

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1
Q

define equilibrium potential for an ion

A

the membrane voltage that a cell needs to be at to prevent movement of that ion down its concentration gradient

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2
Q

what does E stand for? eg Ek or Ena

A

equilibrium potential (of potassium or sodium)

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3
Q

what will stop K+ from leaving cell

A

if the inside is very negative

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4
Q

what will stop Na+ entering cell

A

if inside is very positive

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5
Q

value of Ek

value of Ena

A

-90mV

+50mV

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6
Q

what is Vm

A

resting membrane potential

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7
Q

why is the Vm closer to Ek than Ena

A

because the membrane is about 50x more permeable to K

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8
Q

what happens to Vm when a membrane becomes more permeable to an ion?

A

the ion drives Vm towards its equilibrium potential (by moving down conc gradient)

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9
Q

what is the equation for driving force of an ion?

A

Vm - Eeq

resting mem potential - equilibrium potential of ion

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10
Q

what is driving force of:
K
Na
what does this mean?

A
K =  +20mV forcing K+ out of cell 
Na =    -120mV forcing Na into cell

at rest,
there is a force of +20mV trying to push K out
and
a force of -120mV trying to push Na in

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11
Q

what does the Goldman Hodgkin Katz equation do

A

considers relative permeabilities of ions to calculate Vm

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12
Q

what is the Goldman Hodgkin Katz equation

A

Vm = 58mV x log ( Pk [K+out] / Pk [K+ in] + Pk[Na out] / Pk[Na in] )

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13
Q

why is driving force on sodium greater than on K

A

because it is less permeable to Na

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14
Q

how is an action potential generated

A
  1. depolarisation causes Vm increase towards Ena (gets more positive)
  2. when threshold is reached Na+ channels open causing an Na influx making inside more positive (+ve feedback)
  3. peak
  4. Na channels snap shut
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15
Q

describe repolarisation

A
  1. depolarisation causes slow opening of K+ channels
  2. K+ efflux out
  3. Vm goes back towards Ek
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16
Q

how does an action potential propagate along a neuron

A
  1. during depolarisation the section of the neuron that is depolarised becomes positive (inside) and the rest of the neuron is -ve inside
  2. +ve is attracted to -ve, so the AP conducts to these -ve areas
17
Q

what is balanced in the equilibrium membrane potential of an ion

A

electrical force and osmotic force

18
Q

what is capacitance

A

membranes ability to store charge on either side of the membrane

19
Q

what does nernst equation tell us

A

the membrane potential that will stop the movement of the ion down its conc gradient

20
Q

what is permeability (related to this topic)

what is conductance (related to this topic)

A

the ease at which ions cross the membrane

how many ions get through the membrane