Why do human postganglionic neurones primarily only fire once during a sympathetic burst?
Version of Record online: 28 FEB 2003
Acta Physiologica Scandinavica
Volume 177, Issue 3, pages 247–253, March 2003
How to Cite
Macefield, V. G. and Elam, M. (2003), Why do human postganglionic neurones primarily only fire once during a sympathetic burst?. Acta Physiologica Scandinavica, 177: 247–253. doi: 10.1046/j.1365-201X.2003.01078.x
- Issue online: 28 FEB 2003
- Version of Record online: 28 FEB 2003
- Received 1 November 2002, accepted 15 December 2002
- motor units;
- muscle vasoconstrictor neurones;
- sympathetic nervous system
Aim: Single-unit recordings from muscle vasoconstrictor, cutaneous vasoconstrictor and sudomotor neurones in awake human subjects have shown that they tend to fire only once per sympathetic burst. We review the firing properties of human sympathetic neurones and examine the idea that the short duration of a sympathetic burst may limit the number of times a neurone can fire, using the human skeletomotor system as a model for the sympathetic nervous system.
Results: It is known that human α motor neurones usually fire in long trains during voluntary contractions, but what of their pattern when constrained by a brief burst? We recorded from single motor units in the tibialis anterior muscle while subjects generated brief electromyogram bursts in the intervals between heart beats, with a duration similar to that of muscle sympathetic bursts. Eight motor units fired mostly one spike per burst, with a pattern identical to that of sympathetic neurones.
Conclusion: These results suggests that were it not for the constraint of the bursting pattern, individual sympathetic neurones would – like α motor neurones – tend to fire in long trains.