D’YOUVILLE COLLEGE
BIOLOGY 307/607 - PATHOPHYSIOLOGY
Lecture 21 - PATHOPHYSIOLOGY OF NERVOUS SYSTEM II
Chapter 21
1.
Spinal Nerve Disorders:
• neuromuscular junction disorders, e.g., myasthenia gravis: autoimmune
attack on cholinergic receptors in motor endplates (type II hypersensitivity pattern:
antibody-dependent cellular cytotoxicity) (fig. 5 - 14b, table 5 - 4 & ppt. 1) results in
destruction of junctions and associated muscle; results in muscular weakness
• spinal cord motor neuron disorders, e.g., amyotrophic lateral sclerosis:
initially upper motor neurons (of lateral corticospinal tract) deteriorate, followed by
progressively larger numbers of  motor neurons (figs. 21 - 8, 21 - 13 & ppts. 2 & 3)
resulting in increasing loss of muscular function; fatal in 80% of cases, but some survive
for years; fibrosis of lateral corticospinal tract is common finding postmortem
• spinal nerve entrapments: compression of various peripheral nerves with
resulting disturbance of sensory function (paresthesias) and disturbance of motor
function (paralysis) with potential for muscular wasting; e.g., carpal tunnel
syndrome involves compression of median nerve where it enters the hand (ppt. 4);
treatment may simply involve avoidance of offending movements (orthotics), or in
more severe cases, surgical release of pressure
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2.
- p. 2 -
Disorders of Basal Ganglia:
• basal ganglia (basal nuclei) (fig. 21 - 10 & ppt. 5): deep regions of gray matter
in cerebrum and adjacent midbrain; coordinate programs of motor activity to be
ultimately implemented by motor cortex; communication is via substantia nigra of
anterior midbrain to thalamus and thence to motor cortex (fig. 21 - 7 & ppt. 6)
• Parkinson's disease: principle lesion is in substantia nigra
- difficulty initiating movement; weakened, slowed movements, resting tremors
- idiopathic, not fatal, but life-shortening
- later stages treated with l-dopa, a drug that promotes dopamine formation
(neurotransmitter of substantia nigra)
• Huntingdon's disease: characterized by rapid, writhing, flick-like contortions,
slowing of movements, & progressively profound dementia; governed by dominant
gene allele with functional onset between 35 - 45; lesions of putamen and caudate
nucleus; causes death in about 15 years
3.
Complex Disorders:
• cerebral palsy: multiple disparate patterns of disordered movements + some
cognitive losses
brain damage in perinatal period is cause; non progressive; variable loss
of control over voluntary movement results in uncontrolled reflexes from spinal cord or
lower brain levels; cognitive losses vary from none to severe, often paralleling level of
motor losses; internal brain hemorrhaging in the fetus appears to be an important
cause
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- p. 3 -
• multiple sclerosis: presents a multiplicity of symptoms dependent on
regional involvement; may be post-viral with genetic tendency
- lesion involves demyelination of CNS cells (fig. 20 - 17 & ppt. 7), producing
plaques within brain, cranial nerves, and spinal cord
- temporary visual impairment, loss of motor control, and episodic loss of
emotional control characterize attacks
- periods of exacerbation followed by periods of resolution (often prolonged), with
subsequent return of exacerbated symptoms; usually afflicts 20 - 40 year-old age group
• Alzheimer disease: devastating cortical lesions resulting in dementia -- loss of
self care capabilities, memory loss, loss of ability to recognize, loss of personality, +
bouts of anxiety and depression, inevitably culminating in death
- lesions involve intracellular fibrillary tangles (of proteins) that destroy
neurons and also plaques (amyloid protein) that involve tangled processes & neural
connective tissue cells
- genetic predisposition involves chromosome 21 (which is also related to
Down's syndrome)
• summary of motor disorders (fig. 21 - 17 & ppt. 8)