PERIPHERAL NERVES Flashcards
____ bacterial toxin
acts directly on the membranes of the Schwarm cells near
the dorsal root ganglia and adjacent parts of motor and
sensory nerves
diphtheria
____ causes occlusion of
vasa nervorum, resulting in multifocal nerve infarction
polyarteritis nodosa
_____ protein
synthesis of dorsal root ganglion cells is blocked with
subsequent neuronal destruction
doxorubicin toxicity,
which combines with the axoplasm of the largest sensory
and motor nerves via sulfhydryl bonds
arsenic
____which damages the microtubular transport system.
vincristine
toxicity,
mechanism of histopathological reactions of peripheral nerves
segmental
demyelination, wallerian degeneration, and axonal degeneration
Focal degeneration of the
myelin sheath with sparing of the axon is called _______
segmental
demyelination.
a reaction of both the axon and
myelin distal to the site of disruption of an axon
wallerian degeneration
when the axon degenerates
as part of a “dying-back” phenomenon in a more
generalized metabolically determined polyneuropathy, it
is termed _____
axonal degeneration.
Certain diseases affect the neuron primarily rather
than the axon and cause either a motor or sensory _______.
neuronopathy
By means of ________, the cell bodies receive signals to
increase their metabolic activity and to produce growth
factors and other materials needed for axonal regeneration.
retrograde
axonal transport
These
retrograde changes consist of swelling of the cell cytoplasm
and marginalization and dissolution of the Nissl
substance. The important point again is that despite the
destructive changes in the nerve fibers, the nerve cells,
while altered in histologic appearance, are left intact with
preservation of the apparatus required for recovery.
chromatolysis
T or F
recovery is much slower with
wallerian or axonal degeneration, often requiring months
to a year or more
T
Recurrent demyelination and remyelination lead
to ________formations and enlargement of nerves,
the result of proliferating Schwarm cells and fibroblasts
that encircle the axon and its thin myelin sheath
“onion bulb”
Regenerating axon filaments take
aberrant courses and, with fibroblastic scar formation,
they may form a disorganized clump of tissue termed
_____
pseudoneuroma
This represents the “length-dependent” pattern that is
typical of ______. The nutritional, metabolic,
and toxic neuropathies assume this
axonal degeneratio
By contrast, in demyelinating polyneuropathies, the _______ of lesions and blockage of electrical conduction
often leads to weakness of proximal limb and facial muscles
before or at the same time as distal parts are affected
multifocal
nature
The maximum degree of denervation
atrophy after an acute injury to the axons occurs in _____ and reduces muscle volume by 75 to 80 percent.
90 to
120 days
Ultimately in muscle
atrophy, there is degeneration and loss of the denervated
muscle fibers. This process begins in _________months; in 3 to
4 years,
6 to 12
_______, in which tendon reflexes
may be retained, even with marked loss of perception
of painful stimuli.
small-fiber neuropathies
An ________pattern of sensory
loss over the abdomen and thorax in severe axonal neuropathy
may be mistaken for the sensory level of a spinal cord lesion.
“escutcheon”
Loss of proprioception may also give rise to small
wavering, fluctuating movements of the outstretched fingers–
called _______ or “dancing fingers.”
pseudoathetotic,
Austin pointed out that foot deformity is
found in ___ of patients with hereditary polyneuropathy,
and spine curvature is found in 20 percent
30 percent
Unequal weakening
of the paravertebral muscles on the two sides of the spine
during early development leads to ______
kyphoscoliosis