The Distinction Between a Preganglionic Fibre and a Postganglionic Nerve
Preganglionic fibres and postganglionic nerves aren't anything alike. Any first year medical student could tell them apart.'
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The Chief Medical Officer of Deep Space Nine’s titular space station, Doctor Julian Bashir, famously graduated second in his class at Starfleet Medical (salutatorian), due to confusing a ‘preganglionic fibre for a postganglianic nerve’. At first claiming the error was a ‘trick question’ in his oral examination,1 the antagonistic character created by Bashir’s subconscious, Altovar, later suggested that he intentionally confused the two, perhaps to avoid the ‘pressure’ of coming first.2 It has since been speculated by various fans that the failure to graduate first was an intentional masking of his illegal genetic-enhancements.3 The production reason for Altovar’s accusation is explained by writer Robert Hewitt Wolfe’s paraphrasing of his pre-veterinarian wife, Celeste, claiming that she complained about Bashir’s anecdote in Q-Less, believing that nobody could possibly confuse the nerve from the fibre.4
Terminology
To aptly explain the distinction between a preganglionic fibre and a postganglianic nerve, the terms Bashir is referring to must be clearly identified. Assuming that this medical terminology appertains to modern biology, rather than some science-fiction substitute, Bashir must surely be referring to the autonomic nervous system, the division of the nervous system responsible for the involuntary operation of organs, including heart rate, respiration and blinking.5
Ganglionic or Ganglianic?
Alexander Siddig’s speech and the episode’s script each have Bashir saying ‘postganglianic’ instead of ‘postganglionic’. However, Michael Okuda and Rick Sternbach suggested the correct spelling ‘postganglionic’ be added to the script for the debut episode Emissary, where it was originally intended for Bashir’s blunder to be introduced.6 As later episodes would retroactively correct the term to ‘postganglionic’, it can be assumed that this is the correct term.7
Nerve
Of further ambiguity is that the term ‘nerve’ might refer to nerves (a cabled collection of fibres), nerve tissue, nerve cells (neurons), or nerve fibres. As Bashir consistently recognises a distinction between (nerve) fibres and nerves, it can be reasonably precluded that he is referring to postganglionic nerve fibres, therefore he must instead be referring to postganglionic neurons.
Neuron
While physicists might expect neurons to be a special type of particle, ‘neuron’ is the name of the main cell which comprise the nervous system, depicted in Figure 1. Neurons transmit information across the cell using electrical impulses along their axons, long conductive nerve fibres. These fibres are often sheathed in myelin, an insulator that increases the rate of flow of electric charges across the cell, familiar to physicists as electric current. Neurons interact across synapses by transceiving special molecules known as neurotransmitters.8
Typically, but not definitively, the postganglionic axons are unmyelinated, affording them greater flexibility and a smaller size than the preganglionic nerve fibres, at the cost of information transmission speed.
Ganglia
The axons which interconnect the central nervous system (the brain and spinal cord9) with ganglia are referred to as preganglionic nerve fibres, with the axons interconnecting the ganglia and target organs referred to as postganglionic nerve fibres.10
The ganglia act as junctions which split and reroute signals, containing synapses which carry neurotransmitters between the ganglionic neurons. The connections of the central nervous system with ganglionic cells and effector organs are depicted in Figure 2.
Conclusion
Preganglionic (nerve) fibres are long, myelinated axons which conduct electrical impulses between the central nervous system and ganglia. Postganglionic nerves (neurons) are the cells which contain the flexible and usually unmyelinated axons known as postganglionic nerve fibres. Doctor Julian Bashir, for reasons which may not simply be idle incompetence, mistook a preganglionic nerve fibre for a postganglionic neuron (or bundle of neurons), abbreviating the phrase to ‘a preganglionic fibre for a postganglionic nerve’ and occasionally mispronouncing ‘postganglionic’ as ‘postganglianic’.
Credits & Citations
Diagrams - Wikimedia Commons
OpenStax - ‘Access for free at https://openstax.org’
Screencaps - Cygnus-X1
Screencaps - Trekcore (with subsequent AI upscaling)
Scripts - Star Trek Minutiae
DS9 1x07: Q-Less
DS9 3x18: Distant Voices
DS9 5x16: Doctor Bashir, I Presume?
Erdmann TJ, Block PM. Deep Space Nine Companion. Simon and Schuster; 2000.
Waxenbaum JA, Varacallo M, Reddy V. Anatomy, Autonomic Nervous System [Internet]. Nih.gov. StatPearls Publishing; 2019. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539845/
Reeves-Stevens J, Reeves-Stevens G. The making of Star trek, Deep Space Nine. New York: Pocket Books; 1994.
DS9 3x22: Explorers
Clark MA, Douglas M & Choi J. 35.1 Neurons and Glial Cells - Biology 2e | OpenStax [Internet]. openstax.org. Available from: https://openstax.org/books/biology-2e/pages/35-1-neurons-and-glial-cells
Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH et al, 13.2 The Central Nervous System - Anatomy and Physiology 2e | OpenStax [Internet]. openstax.org. Available from: https://openstax.org/books/anatomy-and-physiology-2e/pages/13-2-the-central-nervous-system
Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH et al. 15.1 Divisions of the Autonomic Nervous System - Anatomy and Physiology 2e | OpenStax [Internet]. openstax.org. 2022. Available from: https://openstax.org/books/anatomy-and-physiology-2e/pages/15-1-divisions-of-the-autonomic-nervous-system