a recurrent period of deep sleep, typically totaling five or six hours a night, distinguished by the presence of slow brain waves and by very little dreaming.
the period of life just prior to sexual maturation
a bitter, alkaline, yellow or greenish liquid, secreted by the liver, that aids in absorption and digestion
the change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated, serving to transmit nerve signals
action in response to a stimulus of a system, a nerve or a muscle