Frame of reference- something that we already know that we can compare new concepts to. Epigenetic factors are environmental influences that change the expression of genetic material: epi means on top of/ in addition to. Junk dna- dna that does(cid:374)(cid:859)t e(cid:374)(cid:272)ode protei(cid:374)s, strands of dna contain switches that turn genes on and off when triggered by the environment. One of the enzyme that influence how proteins (histones) are wrapped around dna is called. If activity is altered and the protein is somehow wrapped differently, this can to memory impairment in mice. 3. 2 the building blocks: cells of the nervous system. Peripheral nervous system is composed of all parts of the nervous system outside of the brain and spinal cord. Neuronal membrane- the lipid bilayer containing the contents of the cell, contributes to a (cid:374)euro(cid:859)s a(cid:271)ilit(cid:455) to (cid:272)o(cid:374)du(cid:272)t ele(cid:272)tri(cid:272)al a(cid:272)ti(cid:448)it(cid:455) 3. 2. 1. 2 the soma and axon work together to send messages.