1.  Schematic representation of the early M response from the distally propagated action potential and the later F wave from the proximally propagated action potential.
 Schematic representation of the early M response from the distally propagated action potential and the later F wave from the proximally propagated action potential. The latter depolarises the axon hillock causing it to backfire. Actual F wave responses are shown in the lower trace. F waves vary in latency and shape due to different populations of axons backfiring each time.
A Mallik, and A I Weir J Neurol Neurosurg Psychiatry 2005;76:ii23-ii31
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