I think that there are some that are always open and some that are not, when the neurone is depolarised after an action potential the potassium ion channels that are closed now open, so all potassium ion channels are now open.
Hope this helps

Reply 5

Jpw1097

19

Original post by Adorable98

I'm just confused, I watched a video were it says that the Potassium channels are always Open, but how come they'd open during repolarisation then?

There are different types of K⁺channels. One type of K⁺ channel is always open and it referred to as a 'leak channel'. This is why cell membranes are fairly permeable to K⁺ ions whereas if you compare it to, say, Na⁺, there are fewer Na⁺ leak channels and so the cell membrane is less permeable to Na⁺ ions. This is one of the reasons why the resting membrane potential is negative.

During repolarisation, it is voltage-gated K⁺ channels which open when the membrane potential is around 40mV and then close at around -75mV (which is why the cell becomes hyperpolarised).

Reply 6

Adorable98

OP

15

Original post by Jpw1097

There are different types of K⁺channels. One type of K⁺ channel is always open and it referred to as a 'leak channel'. This is why cell membranes are fairly permeable to K⁺ ions whereas if you compare it to, say, Na⁺, there are fewer Na⁺ leak channels and so the cell membrane is less permeable to Na⁺ ions. This is one of the reasons why the resting membrane potential is negative.

During repolarisation, it is voltage-gated K⁺ channels which open when the membrane potential is around 40mV and then close at around -75mV (which is why the cell becomes hyperpolarised).

Oh, I see!!! Thank you!! :smile:

Reply 7

Adorable98

OP

15

Original post by Jpw1097

There are different types of K⁺channels. One type of K⁺ channel is always open and it referred to as a 'leak channel'. This is why cell membranes are fairly permeable to K⁺ ions whereas if you compare it to, say, Na⁺, there are fewer Na⁺ leak channels and so the cell membrane is less permeable to Na⁺ ions. This is one of the reasons why the resting membrane potential is negative.

During repolarisation, it is voltage-gated K⁺ channels which open when the membrane potential is around 40mV and then close at around -75mV (which is why the cell becomes hyperpolarised).

Are there different types of sodium channel too?

Reply 8

Adorable98

OP

15

Original post by wabbit998

I think that there are some that are always open and some that are not, when the neurone is depolarised after an action potential the potassium ion channels that are closed now open, so all potassium ion channels are now open.
Hope this helps

Oh, I see! Are the sodium channels always open too?

Reply 9

Luke1234321

3

Original post by Adorable98

Oh, I see! Are the sodium channels always open too?

No, i don't think so.

Reply 10

thegodofgod

19

Original post by Adorable98

Are there different types of sodium channel too?

Yes. There are fewer leaky Na⁺ channels than leaky K⁺ channels, meaning that membranes generally tend to be less permeable to Na⁺ than K⁺ at rest.

Original post by Adorable98

Oh, I see! Are the sodium channels always open too?

Leaky Na⁺ channels, like leaky K⁺ channels, are always open. Voltage-gated Na⁺ channels, as suggested in the name, open and close at specific ranges of voltage (activated at around -70 mV, which causes depolarisation when there is an influx of Na⁺ into an excitable cell, and closed at around +40 mV, which causes no further depolarisation when the influx of Na⁺ stops).

Bear in mind that there are different types of voltage-gated Na⁺ channels, so they open and close at different voltage ranges (cf. the funny current in heart tissue).