N.Wells
Posts: 1836 Joined: Oct. 2005
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Quote (GaryGaulin @ May 15 2015,20:26) | There is also good evidence that the giraffe dissection video only shows the movement does not know about time delays for resonant cavaties and could be very wrong about the unusually long larygeal nerve having no function/purpose. |
Lay off the BS, Gary.
There's no obvious causal relationship between your supposed nerve signal delay and "length of a resonance chamber".
First, the giraffe's "resonating chamber" is not the length of its throat, just the length of its larynx, and to a lesser extent the portion of the throat above, but the giraffe's larynx is pretty much at the top of its throat, just like ours.
Second, all the sound-producing muscles of the larynx except one are innervated by the recurrent laryngeal nerve rather than the superior nerve. The exception is the cricothyroid muscle, which tensions the vocal folds, thereby resulting in higher pitch phonation: no signal lag or exceptional resonating chamber length are involved. The cricothyroid muscle works at the bottom of the larynx, but is enervated by the shorter, upper, nerve, while the lower (left recurrent) nerve enervates muscles at the top, middle, and bottom of the larynx.
Third, there is no signal lag. Synchronized nerve signal arrival is important in functions like coughing and swallowing as well as coordinating the cricothyroid muscle with the other phonation muscles, but this is taken care of not by delay or lag in signal arrival but by differential myelination (thicker myelin sheathing on the longer nerve, causing faster signal transmission): D.F.N. Harrison, 1981, Acta Oto-laryngologica, 1981, Vol. 91, No. 1-6 , Pages 383-389, "Fibre Size Frequency in the Recurrent Laryngeal Nerves of Man and Giraffe". Quote | An Optomax Image Analyser has been used to carry out fibre-size analyses in six pairs of human recurrent laryngeal nerve and two pairs of recurrent nerves from adult giraffes. in every case the left recurrent laryngeal nerve was found to contain a greater number of large, fast-conducting fibres. Since this nerve is longer than the right, these findings may explain the simultaneous arrival of motor impulses to both sides of the laryngeal musculature. |
So, studies have been done and biologists know about these things, contra your charges, and there is no lag between the two nerve signals, contra your expectations, and there is no required correlation between resonance chamber length and nerve lag time. Again, there is no lag. This has been pointed out to you earlier in this thread, so at this point you are lying.
Note the pattern here: once again you are spouting ignorant and untruthful BS because you think it sounds good and because it supports the way you want things to be. Is it surprising that you have NO credibility left?
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