UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Some factors affecting nerve conduction

Fern, Robert; (1992) Some factors affecting nerve conduction. Doctoral thesis (Ph.D), UCL (University College London). Green open access

[thumbnail of out.pdf] Text
out.pdf

Download (6MB)

Abstract

In the past compound action potential recording has been widely employed to investigate patterns of nerve conduction block. This technique, however, has a number of methodological drawbacks which do not apply to the unitary action potential recording technique. In this thesis unitary potentials have been recording during a number of types of nerve block to gain a better understanding of the underlying events. It was found that 250 mmHg of pressure applied to the isolated frog nerve generated a differential block of fast myelinated axons as a result of nerve fibre deformation. However, nerve ischaemia (studied in the cat sciatic nerve) was found to have the opposite effect, generating a differential block of slow axons. Conduction block induced by compression in vivo was found to have a similar pattern to that induced by ischaemia when of the order associated with the clinically prevalent carpel tunnel syndrome. More extreme compression however, of the order associated with clinically acute compression lesions, was found to differentially affect fast axons, suggesting that block is due to physical trauma under these conditions. Experiments were also performed to evaluate how the structure-function relationship of the frog myelinated axon influences the axons' response to changes in ionic environment. It was found that perfusion of frog myelinated axons with a high potassium concentration induced slowing in action potential conduction velocity over a diphasic time course, apparently due to potassium diffusing into both the perinodal and the periaxonal compartments. Potassium diffusion into the periaxonal space was found to have profound effects upon nerve conduction, while the slow evolution of these effects indicates effective potassium ion homeostasis beneath the myelin sheath. In contrast to high potassium perfusion, low sodium perfusion produced simple monotonic changes in conduction velocity, affecting the slowest group of axons to the greater extent. This confirms an earlier theoretical prediction that small myelinated axons have a low safety factor and may explain the differential action of local anaesthetics. An assessment was also made of the use of compound action potential recording as a technique to investigate changes in nerve conduction. This showed that compound action potentials are a valuable tool for evaluating qualitative changes in nerve conduction, but are not appropriate for demonstrating the specific block of a group of axons.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Some factors affecting nerve conduction
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Action potential recording
URI: https://discovery.ucl.ac.uk/id/eprint/10121082
Downloads since deposit
1,761Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item