Year 12s: what will be the first way you research your future options? >>

Axon diameter

arvin_infinity

Wondered why larger diameter of axon causes greater speed of transmission. :redface:

MS: "Less leakage of ions from wider axon"

Didn't quite get why less leakage.

+rep

Reply 1

007007

With a larger diameter, there is less resistance. Hence increased conduction velocity

This was posted from The Student Room's Android App on my GT-I9100

Reply 2

arvin_infinity

Original post by 007007

With a larger diameter, there is less resistance. Hence increased conduction velocity

This was posted from The Student Room's Android App on my GT-I9100

Well I do understand that but I dind't understand the mark scheme ..
I wouldn't get the mark by saying anything else apart from that marking point..there is no AVP in the mark schem

Reply 3

007007

Ok, well then I imagine that the larger size of axon entails a relatively lower surface area for ions to leak...?

Mark schemes are so restrictive

This was posted from The Student Room's Android App on my GT-I9100

Reply 4

arvin_infinity

Original post by 007007

Ok, well then I imagine that the larger size of axon entails a relatively lower surface area for ions to leak...?

This was posted from The Student Room's Android App on my GT-I9100

Larger size of axon gives lower SA? :s-smilie:

Mark schemes are so restrictive

I know right.. :colone:

Reply 5

Hazza616

The surface area to volume ratio would be lower i think. Thats such an obscure answer though :s-smilie:

Reply 6

Arekkusu

Surface area is basically the answer to every single question in biology

Reply 7

NinjaRikki

Original post by arvin_infinity

Wondered why larger diameter of axon causes greater speed of transmission. :redface:

MS: "Less leakage of ions from wider axon"

Didn't quite get why less leakage.

+rep

Basically, this is my interpretation after researching it, as I was confused like you are. Essentially what books say is the larger the diameter the faster an impulse is conducted because less leakage and ions have less resistance to movement.

I can only expand on my latter point. As the axon is wider, ions collide less when either being actively moved by the sodium-potassium pump or diffusing through the sodium or potassium channels, and so as there is less resistance (LIKE IN GEL ELECTROPHORESIS) the ions move faster, meaning adjacent regions depolarise at a faster rate i.e. impulse conducted at higher rate :smile: