The Neuron/Nervous System
This refers to the extent to which the differences among groups can be explained by genes
heritability
Part of the endocrine system, this structure secretes melatonin and helps regulate sleep cycles.
Pineal Gland
No larger than a pea and located at the base of the brain, this "master" gland controls the functions of many other glands.
Pituitary gland
This inhibitory neurotransmitter lessens a nerve cell's ability to receive, create or send chemical messages to other nerve cells, producing a calming effect.
GABA