state blocks vesicle fusion with the presynaptic membrane. Gap junctions
are not involved (answer e).
143.The answer is d.(Junqueira, pp 154, 156–157, 163–165.)The left
hemisphere regulates language and speech and the right hemisphere con-
trols nonverbal, spatial skills such as the ability to draw or play music. If
the right side of the brain is damaged, movement in the left arm and leg,
vision to the left, or hearing in the left ear, may be affected. An injury to the
left side of the brain affects speech and movement on the right side of the
body. Pyramidal neurons are labeled with the arrows in the photomicro-
graph. Axons are evident in the histologic section arising from the axon
hillock. Neither the axon nor the axon hillock contains Nissl substance
(rough ER), which is dispersed throughout the soma and dendrites. Den-
drites generally are wider than axons, are of nonuniform diameter, and
taper to a point. Motor neurons, such as those illustrated in the photomi-
crograph, usually display large amounts of euchromatin, distinct nucleoli,
and Nissl (if stained appropriately) characteristic of high synthetic activity.
144.The answer is a.(Junqueira, pp 172–173, 175. Kasper, pp 966–969.)
The woman in the scenario has contracted leprosy with infection of the
peripheral nerves by Mycobacterium leprae. Perineurial inflammation of
cutaneous nerves leads to distal anesthesia and paralysis, which are major
clinical features of the early stages of leprosy. Those neuropathic changes
are eventually responsible for the deformities that elicit most of the social
stigma associated with leprosy. The neuropathy of leprosy primarily affects
the facial, ulnar radial and peroneal nerves with ascending degeneration of
the nerves. In the later stages, endoneurial inflammation, infection of
Schwann cells, demyelination, and reduced conduction velocity occurs. In
the high-magnification light micrograph, several cross-sections through
small peripheral nerves are visible. Cindicates the perineurium, a layer of
two to three fibroblast-like cells with contractile properties that surround
individual fascicles. Cells of the perineurium are joined by tight junctions
and form a barrier to macromolecules. Bindicates the dense, irregular con-
nective tissue part of the epineurium surrounding the entire nerve. There
are numerous nerve fibers surrounded by myelin sheaths (D)produced by
Schwann cells (nucleus visible at E). Other nuclei visible within the fascicle
include those of fibroblasts, which secrete the reticular connective tissue ele-
ments forming the endoneurium surrounding the individual neuronal
fibers, and nuclei of capillary endothelial cells. Neuronal perikarya are not
246 Anatomy, Histology, and Cell Biology