51) Myelin on axons functions to
A) make the axons live longer.
B) store nutrients (fat) for use by the neurons.
C) cover nodes of Ranvier.
D) speed the rate of impulse conduction and insulate neighboring axons from one another.
52) Which cells provide the myelin sheath for neurons in the PNS?
A) astrocytes
B) microglial cells
C) Schwann cells
D) oligodendrocytes
53) Nonmyelinated axons
A) are thicker than myelinated axons.
B) are not associated with any Schwann cells.
C) conduct impulses more slowly than myelinated axons.
D) occur in the PNS, but not in the CNS.
54) Which of the following most immediately encases the smallest component of a nerve?
A) endoneurium
B) epineurium
C) fascicle
D) perineurium
55) Motor neurons arise primarily from the
A) alar plate.
B) basal plate.
C) ependyma.
D) neural crest.
56) A nerve cell is the same as a
A) nerve.
B) nerve fiber.
C) neurilemmocyte.
D) neuron.
57) An example of proprioception is
A) the contraction of the triceps brachii.
B) the contraction of pharyngeal arch muscles used in chewing.
C) sensing a feather touch the skin.
D) the sensation you feel during a wake-up stretch.
58) Sensory neurons arise primarily from the
A) neural crest.
B) alar plate.
C) basal plate.
D) neural tube.
59) Some small neurons in the CNS have no axon, only dendrites, and are
A) multipolar.
B) bipolar.
C) unipolar.
D) pseudounipolar.
60) A man walking barefoot stepped on a piece of glass. His foot jerked upward in which type of reflex?
A) somatic, polysynaptic withdrawal reflex
B) visceral, monosynaptic stretch reflex
C) somatic, monosynaptic withdrawal reflex
D) visceral, polysynaptic withdrawal reflex