Session 5 extras

Question 1

Are myelinated nerve fibres in the CNS or PNS easier to regenerate?

Answer 1

PNS

Question 2

What happens to a myelinated nerve fibre that has been completely demyelinated?

Answer 2

Ion channels spread out across axon from previous nodes of Ranvier
behaves like unmyelinated axon

Question 3

Is partial demyelination or complete demyelination worse?

Answer 3

Partial demyelination

Question 4

How does the duration of the internodal delay compare to the refractory period in a myelinated axon? Why?

Answer 4

Internodal delay is shorter than refractory period

because if it was longer, the action potential could travel backwards along the axon

Question 5

Are myelinated axons or demyelinated axons easier to stimulate? Why?

Answer 5

Myelinated axons
because myelination increases resistance, less ions leak out, more of them stay in the axon and depolarise the axon hillock to threshold