nerve impulses Flashcards

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1
Q

what is the resting potential volatge

A

-70

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2
Q

why is this

A

because their are more positively charged ions on the outside of the neurone

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3
Q

what is resting potential

A

the potential differance across the membrane while the neurone is at rest.

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4
Q

during resting potential how is the potential difference altered

A

na+ and k+ pump at 3na+ out of the cell and 2k+into cell

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5
Q

what does this result in

A

there fore their is a higher concentration of Na+ outside and more k+ inside

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6
Q

what does this cuase the na+ and k= ions to do

A

na+ diffuses in and k+ diffuses out

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7
Q

however why does the inner membrane remane more negative - -70

A

because more Na+ channels are closed and the plasma membrane is more permeable to k+ ions

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8
Q

how is resting potential maintained

A

through the sodium potassium pump

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9
Q

what does this require

A

ATP

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10
Q

what does the sodium potassium pump do

A

sodium potassium pump moves 3 na+ ions outside the cell and two k+ ions to the inside of the cell

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11
Q

if k+ move into the nerve cell how come the resting is - 70

A

because the k+ ions have moved in it creates a concentration gradient of pottassium ions inside the cell and so k+ ions diffuse out the neuron creating a negative resting potential

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12
Q

why do sodium ions not just diffuse back through

A

sodium potassium pump becomes less permeable to na+ ions so they cant be transported

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13
Q

what causes the start of action potential

A

when a stimulus is received by the receptors

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14
Q

what does this change in stimulus cause

A

sodium channels open so more Na+ ions diffuse through

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15
Q

what does this cause

A

depolarization

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16
Q

what is depolerisation

A

when the inside of the neuron becomes more positively charged

17
Q

what is the threshold potential

A

-50v

18
Q

what happens if depolerization reaches -50v

A

more voltage gated sodium ion channels are opened- higher influx

19
Q

what does this cause the action [potential to change to

A

+40v

20
Q

after depolerization occours what happens

A

repolerisation

21
Q

what is repolerisation

A

the potential of the neurone is returning back to a negative state

22
Q

how does repolerization occour

A

more voltage gated k+ channels open and k+ ions leave the neuron

23
Q

when most of the potassium ions leave the neuron what does this cause

A

hyperpolerization

24
Q

what is hyperpolerisation

A

when the charge of the neuron drops bellow its resting

25
Q

is this temporary

A

yes

26
Q

what is done to fix it

A

sodium potassium pump returns neuron back to resting state