44. Most CNS neurons lack centrioles. This observation explains: A) why CNS neurons grow such long axons. Bwhy CNS neurons cannot divide to regenerate damaged tissue. C) the ability of neurons to generate an action potential. D) the ability of neurons to communicate with each other. E) the ability of neurons to produce a resting potential. 45. Which of the following help to protect the brain? A) the blood-brain barrier B) the bones of the skull C) the cranial meninges D) the CSF Eall of the above are correct. 46. Pupillary muscle groups are controlled by the autonomous nervous system (ANS). Parasympathetic activation causes pupillary ,and sympathetic activation causes A) dilation; constriction B) dilation; dilation Cconstriction; dilation D) constriction; constriction E) vasoconstriction; vasoconstriction 47. Which of these anatomical sequences is correct? A) tympanum; incus; malleus; stapes; oval window; round window B) tympanum; incus; malleus; stapes; round window; oval window Ctympanum; malleus; incus; stapes; oval window; round window D) tympanum; incus; stapes; malleus; oval window; round window E) tympanum; malleus; incus; stapes; round window; oval window