make profuse inhibitory dendritic contacts with the flask-shaped Purkinje
cells. Each Purkinje cell receives about 2 × 105 synapses, mostly onto its
dendritic spines which splay out across the molecular layer. Granule cells
are small neurons located in the vicinity of the Purkinje cells. Granule cell
axons form the parallel fibers that make excitatory synapses onto Purkinje
cell dendrites. Each parallel fiber synapses on about 200 Purkinje cells cre-
ating an excitation strip across the cerebellum.
138.The answer is b.(Young, p 133. Junqueira, p 158. Kierszenbaum, pp
28–29. Kasper, pp 1042–1044. Moore and Dalley, pp 85–87.)Kinesin is a motor
protein that uses energy from ATP hydrolysis to move vesicles (– →+)from
the cell body in the dorsal root ganglion (shown in the photomicrograph)
in an anterograde direction toward the axon terminal (answer d).The
patient in question has shingles caused by the herpes virus known as the
varicella-zoster virus (VZV). Shingles begins as erythematous maculopapu-
lar eruptions and rapidly evolves to vesicles; it often presents with fever.
The patient had chickenpox as a child. Chickenpox is also caused by VZV.
The virus is stored in the dorsal root ganglion, primarily in the satellite cells
surrounding the perikarya (cell bodies). Kinesin walks along the micro-
tubule toward the plus end of the microtubule. The dyneins (answers a
and c)are minus-end directed microtubule motors that move organelles,
including vesicles, in a retrograde direction toward the cell body (in this
case toward the cell bodies of the dorsal root ganglia). The dyneins
involved in axonal transport are the cytoplasmic dyneins as compared to
the axonemal dyneins seen in cilia and flagella. Myosin II (answer e)is an
actin-based motor protein that generates the force of muscle contraction.
The Tzanck test is a method of testing for the virus; it can detect the pres-
ence of the herpesvirus in the cells scraped from a lesion. It cannot detect
the difference between herpes simplex virus (HSV) and VZV. PCR of the
DNA is required for absolute detection.
The patient’s shingles involve dermatomal segment T4, which sur-
rounds the nipple. The nipples are normally found in the middle of T4,
although T5 may also innervate this region. A dermatome is the area of skin
supplied by nerves originating from a single spinal nerve root.
139.The answer is c.(Junqueira, pp 179–180. Ross and Pawlina, p 351.
Kierszenbaum, pp 30, 216. Alberts, pp 979–981. Kandel, pp 99–103, 1108–1109.)
Regeneration depends on the proliferation of Schwann cells, which guide
Nervous System Answers 243