[HAPS-L] Terminologia Histologica / Neuromuscular junctions

[Ken Saladin <ksaladin@xxxxxxxxxx>]

For what few responses there have been so far, we seem to agree on HAPS-L (and even more in our A&P textbooks) that "motor end plate" means the depressed area of the sarcolemma that receives the motor nerve fiber terminals. Yet it's hard to find a medical dictionary, neuroscience textbook, or histology textbook that agrees with this.

Someone here, maybe Lee Weller, once said that there is a Terminologia Histologica in preparation, and such a thing might help to establish how we should use this term. Does anyone reading this know the status of that project? I found online minutes of a June 2005 meeting of the International Federation of Associations of Anatomists that said the TH was due to be published in 2005 and a Terminologia Embryologica in 2006/07. I can't find any indication online that the TH has actually been published, however. The major online booksellers (Amazon.com and BarnesAndNoble.com) recognize the TA but not the TH. I'm sending out some e-mail inquiries to various people associated with the Federation to see if I can get an update on this.

I found a German web site today (Elektronenmikroskopischer Atlas im Internet, http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/ EM/EMmotEndplatte.html) that cites the Terminologia Histologica and says motor end-plate = neuromuscular junction = myoneural junction = synapsis neuromuscularis.

It says in relevant part:
"Eine neuromuskuläre oder motorische Endplatte = myoneurale Synapse (Terminologia histologica: Synapsis neuromuscularis, englisch: motor endplate, neuromuscular junction oder myoneural junction) stellt die Endigung einer somatomotorischen Nervenfaser zur Skelettmuskulatur dar und dient der Steuerung (Innervation) der Muskulatur. Es handelt sich also um eine spezialisierte chemische Synapse, deren flachovale, zur Muskulatur hingewandte Oberfläche ca. 4 bis zu maximal 40 µm im Durchmesser groß ist."

My loose translation: 
"A neuromuscular or motor end-plate = mynoneural synapse (Terminologia Histologica: synapsis neuromuscularis; English: motor endplate, neuromuscular junction, or myoneural junction) represents the ending of a somatic motor nerve fiber on a skeletal muscle fiber and serves for the control (innervation) of the musculature. Thus it acts as a specialized chemical synapse with a flat, ovoid surface on the muscle fiber ranging from about 4 to 40 µm in diameter."

If the Terminologia Histologica is going this route, and in the absence of any contrary usage (much less consensus) in neuro and histo textbooks, we perhaps need to change the terminology in our A&P texts. I'm inclined to think it might be best to avoid the expression "motor end-plate" altogether for now, and just refer more generically to the sarcolemma or the postsynaptic membrane--describing its indentation and its junctional folds but perhaps not giving the general area of membrane any special name. 


Ken