MCAT Question A Day - 6/11/14 - Answer!

Which of the following is found in vertebrates but NOT in invertebrates?

A. a dorsal. hollow nerve chord

B. mylenation to increase the speed of nervous impulse transmission along the axon

C. axons through which the nervous impulse is conducted

D. Na⁺/K⁺-pump

B is correct. Invertebrates do not have myelinated axons to accelerate nervous impulse transmission. Instead, they rely upon increased size. Invertebrate is a subphylum of Chordate which is characterized by a dorsal nerve chord at some point in their development.

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