3.2 AGE-RELATED TISSUE CHANGES
Central nervous system
In most organs ageing results in reduced cell division and replacement of active
cells with connective tissue, however in the brain there is little connective tissue
and postmitotic neuronal death results in a proliferation of active glial elements.
With advancing age the CNS may undergo morphological and chemical changes (see Table
3.1 and Table 3.2).
Peripheral nervous system
Segmental demyelination and wallerian-type degeneration have been described to occur
with advancing age in humans, but the changes are usually mild. Slowing of peripheral
and central nerve conduction has also been demonstrated in elderly people.
Peripheral neuropathies may develop secondary to metabolic diseases such as diabetes
mellitus. In the cat diabetic neuropathy is associated with distal axonal degeneration
and affected animals show hind limb paresis with distal muscle atrophy and hyporeflexia.