What occurs when a nerve is stretched past the capacity of the surrounding structures?
A. Tensile stress develops in the neural tissues.
B. Axons unfold.
C. The external epineurium stretches.
D. None of the above occurs.
ANS: A
Rationale: As a nerve is stretched, first the viscoelastic tubes formed by the endoneurium, perineurium, and external epineurium stretch; the axons unfold; and the fascicles glide relative to each other. As the stretching continues, the entire nerve slides relative to surrounding structures. As stretching continues and exceeds the capacity of these mechanisms, tensile stress develops in the neural tissues. As the nerve is shortened, the processes reverse—the tensile stress is relieved first, then the nerve slides relative to surrounding structures, the viscoelastic tubes recoil, and the axons fold. The nerve may also fold because the median nerve does so at the flexed elbow.
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