NCS-FACTORS INFLUENCING LATENCY, CV, AMPLITUDE

SUMMARY

CV & LATENCY
1. Cold & advancing age slows CV.

2. Cold also increases amplitude & prolongs latencies as it slows the opening & closing of sodium channels, hence inreasing the exchange of sodium across the axon plasma membrane.

3. Disease states reduce amplitude & prolong latencies.

4. CV for a newborn is 50% that of an adult. At 1 year, it is 80% that of an adult. It is equal to an adult by 3 to 5 years.

5. Loss of myelin causes decreased CV, increased onset & peak latencies.

AMPLITUDE
6. Amplitude is also dependent upon the distance from the generator source.

7. SNAP amplitudes will be reduced if sensory axons are disrupted anywhere from their cell bodies (DRG): axons undergo wallerian degeneration, and by 10 days the distal response will disappear.

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].