Edexcel A2 Biology Unit 5 (6BIO5) - 22/06/2011- OFFICIAL THREAD !

You have the PQRS complex? electrocardiogram records the electrical activity of the heart, the heart muscle depolarises as it loses electrical activity when it contracts and repolarises when it relaxes.

The Electrocardiograph records changes by using electrodes placed on the chest :wink:

CONNOR you explained the ECG ! lol he asked hot to measure heart rate from it ! :tongue:

Reply 3981

sammy-lou

16

Original post by ConnorB

You seem to be forgetting that there are K+ ions aswell?!

Read this http://faculty.washington.edu/chudler/ap.html

It will help loads :smile:

That websites brilliant, I found this little animation on it - so helpful!

http://brainu.org/files/movies/action_potential_cartoon.swf

Also, does anyone have a copy of the January 2012 Unit 5 paper? I didn't sit it and can't get it off the edexcel website. Would be forever grateful if anyone could send me a copy!

(edited 11 years ago)

Reply 3982

iesians

6

Original post by PhantomPhreek

That is seriously wrong, the ratio has nothing to do with the potential, it's the permeability of the membrane to the two different ions that determines the potential. The membrane is more permeable to K+ ions moving out than Na+ moving in, this determines the potential not the Sodium potassium pump.

GOOSHH it doesnt make sense.
hyperpolarisation is that its more negative inside right ??!?!?
so how is this corrected ??
Na/K pump pumps Na+ ions OUT and K+ ions in right ? but K+ ions again diffuse out due to permeability. so overall theres more positive out !? THIS ISNT HELPING AT ALL ! its making inside even more negative ??! BIOLOGY FAIL :tongue:

Reply 3983

iesians

6

Original post by sammy-lou

That websites brilliant, I found this little animation on it - so helpful!

http://brainu.org/files/movies/action_potential_cartoon.swf

Also, does anyone have a copy of the January 2012 Unit 5 paper? I didn't sit it and can't get it off the edexcel website. Would be forever grateful if anyone could send me a copy!

lol i love it !!
the Na pump was so mean ! it threw the Na and K ions ! :tongue:

Reply 3984

rudizzy123

5

If you dont do chemistry its an absoloute mare to remember all the different chemicals. Calcium ions involved in neurotransmitter release, negative chloride ions involved in unexcitory synapses, sodium and pottasium involved in depolarisation. Am i right? :smile:

Ps thank you for the answers to my previous question

Reply 3985

iesians

6

Original post by rudizzy123

If you dont do chemistry its an absoloute mare to remember all the different chemicals. Calcium ions involved in neurotransmitter release, negative chloride ions involved in unexcitory synapses, sodium and pottasium involved in depolarisation. Am i right? :smile:

Ps thank you for the answers to my previous question

when does that happen ??!
i think im loosing my senses right b4 the exam :tongue:

Reply 3986

19941994

When a nerve fibre is depolarised, and you're describing it, so saying the 'Na+ ions flow rapidly into the axon' .. Would you say 'axon'? My notes change between 'cell' and 'axon' lol so unsure of which one to use :s

This was posted from The Student Room's iPhone/iPad

Reply 3987

iesians

6

Original post by 19941994

When a nerve fibre is depolarised, and you're describing it, so saying the 'Na+ ions flow rapidly into the axon' .. Would you say 'axon'? My notes change between 'cell' and 'axon' lol so unsure of which one to use :s

This was posted from The Student Room's iPhone/iPad

yup say axon ! even cell can be said because the entire thing is a nerve CELL !
so i think both are correct.

Reply 3988

iesians

6

http://www.scribd.com/doc/89838095/Scientific-Article-Questions-Answers-by-Stafford-Final

this seriously is heaven ! thats to M Kh !!!!

Reply 3989

iesians

6

guys can we revise muscles and heart and all of that stuff cuz i think that has the most chances of coming.

Reply 3990

19941994

Original post by iesians

yup say axon ! even cell can be said because the entire thing is a nerve CELL !
so i think both are correct.

Oh good thanks a lot :smile:

This was posted from The Student Room's iPhone/iPad

Reply 3991

rudizzy123

5

Original post by iesians

when does that happen ??!
i think im loosing my senses right b4 the exam :tongue:

Because inhibitory synapses are at a resting potential of -90mv, not -70mv. This happens due to neurotransmitters from inhibitory synapses opening negative chloride channels and postive potassium channels in the postsynaptic membrane. So K flows out and Cl flows in, the result is a -90mv resting potenital making it harder for the post-synaptic membrane to depolarise :smile:

Reply 3992

iesians

6

Original post by rudizzy123

Because inhibitory synapses are at a resting potential of -90mv, not -70mv. This happens due to neurotransmitters from inhibitory synapses opening negative chloride channels and postive potassium channels in the postsynaptic membrane. So K flows out and Cl flows in, the result is a -90mv resting potenital making it harder for the post-synaptic membrane to depolarise :smile:

oh you were talkin about inhibitory !
now i get it ! :tongue:

Reply 3993

Bright

11

I am going to practically revise this whole unit in 1 and a half days! (half yesterday).

Can someone teach me respiration please?

(edited 11 years ago)

Reply 3994

Rmharr

Original post by sammy-lou

That websites brilliant, I found this little animation on it - so helpful!

http://brainu.org/files/movies/action_potential_cartoon.swf

Also, does anyone have a copy of the January 2012 Unit 5 paper? I didn't sit it and can't get it off the edexcel website. Would be forever grateful if anyone could send me a copy!