- wear and tear vs. use it or lose it
- cumulative toxins
a. free radicals
b. heavy metals
c. neuron specific (insecticides, etc.)
d. non-specific (solvents, etc.)
- stress
a. type II corticosterone receptors
b. sustained hormonal dysfunction
- genetic
a. disease state = mutation
b. programmed cell death
- cholinergic
- excitotoxic
- calcium