Michel Coppieters, who obviously reads in rather obscure places, sent me this article from this month’s Current Biology – Stretchy nerves are an essential component of the extreme feeding mechanisms in rorqual whales”, by Vogl et al.
Rorqual whales such as the blue whale, feed by engulfing water laden with krill. They can take in a massive amount of water equal to the volume of the whale itself. This requires the jaw to open very widely, and the tongue and ventral grooved blubber (VGB) to accommodate.
Vogl et al. have recently demonstrated how stretchy the nerves have to be to allow this feeding function – they could be easily stretched to over double their resting length with folded fascicles (bundles of nerve fibres) unfolding.
This physical feature is a necessity to allow the primary role of impulse conduction to be unhindered.
Humans dance the Fontana!
Human nerves, while not quite so stretchy are similarly constructed. Nerves such as the occipital nerves with neck movement, the infrapatellar branches of the saphenous nerves during squatting, and the nerves of the upper arm during shoulder elevation, all go through remarkable physical challenges – they not only stretch, they also slide in relation to surrounding structures. The median nerve can slide about two centimetres in relation to surrounding tissues. Neurones do their own microscopic dance – I have always thought of this dance as the Fontana, where folded neurones – known as the “spiral bands of Fontana”, unfold during loading. And even more than that, myelin sheaths slide on each other, clefts in the myelin widen, and nodes of Ranvier widen. Much of this work was done in the 60s and then forgotten. I reviewed it quite recently in Mobilisation of the Nervous System in 1991! The brain is so trendy these days that peripheral nerves have been forgotten.
But maybe think of the dance of the Fontana and the remarkable mouth of the blue and fin whales and ponder what the loss of this remarkable movement could do to symptoms and function.
Vogl, AW et al (2015) Stretchy nerves are an essential component of the extreme feeding mechanism of rorqual whales. Curr Biol 25: R360-R361