Edexcel GCE Biology Unit 5 6BI05 June 2013

I understand the stuff on synapses up to where the membrane depolarises and initiates an action potential, but then it's the stuff on axons that confuses me.

Just to add to the above, depolarisation/repolarisation are a result of positive feedback. For example, during depolarisation, the more sodium ions that flow into the axon, the more positive the axon becomes which triggers the opening of more Na+ channels.

Also, depolarisation only occurs at the nodes of Ranvier. The myelin sheath acts as an electrical insulator conducting electrical currents between the nodes through saltatory conduction which helps speed up action potential propagation.

Ah I hope I answered the correct question haha!

We're speaking about a non myelinated neurone.

My bad. It's the same process though as you described above for myelinated neurones apart from the fact that depolarisation can only occur at nodes.

Does the axon membrane depolarise to +40mV?

Has anyone made a list of topics in relation to the pre-release?

or A list of questions?

Where do the Schwann cells and nodes of Ranvier stuff come in? Is it something completely different?

Myelinated neurones. Page 208 Edexcel SNAB textbook.

So, in myelinated neurones, nodes of Ranvier just speed up the movement of an impulse along the axon, and there's a layer of myelin sheath around the axon which is made up of Schwann cells. If the axon is unmyelinated, the movement of nerve impulses along the axon is slower?
Also, are nodes of Ranvier in both myelinated and unmyelinated neurones, or just myelinated ones?

Thanks

The myelin sheath speeds up the conduction of local currents between the nodes where all the usual steps happen (depolarisation etc.). Yes, movement is slower in unmyelinated axons. There aren't nodes specifically no. There are also degrees of being myelinated. So the more myelinated a sheath is, the faster it will conduct too.

This is the mock (questions and answers) that we did in class for the pre release. Our teachers made the questions and mark schemes

Hi,

I am having problem to download this material.Although it seems stupid, but I am stuck. Please help me.

HEY GUYS
i read the article and sounds quite interesting...but i got a slight problem in understanding the phrase below from paragraph 40 page 6
'we also find it very intriguing that the naked mole rat neurons exhibit some electrophysiological properties that suggest neurons in these animals retain immature characteristics'
please someone help me what this phrase is trying to tell us.
thank you

This is an example of Behavioural Adaptation, right?