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(1) In physiology, the time from the moment of stimulation of an organism, organ, tissue, or cell until the manifestation of a responsive reaction.
The duration of the latency period depends on the level of phylogenetic development, individual development, and functional state of the body and on the complexity of the reaction and the speed of the processes in its peripheral and central links. Thus, the latency period of a given reflex consists of the time it takes to transform the energy of the external stimulus in the receptor, the time necessary to conduct the excitation along the nerve fibers, the duration of the synaptic lags, and the time required to trigger the effectors.
The latency period of psychological reactions characterizes the level of wakefulness and the states of attentiveness and tension. Determination of the magnitude of the latency period is of great importance in physiology, medicine (for studying the functions of the healthy and the diseased body), and experimental psychology.
(2) The latency period of pregnancy is a temporary lag in the development of the fertilized ovum in certain mammals; during the late blastula stage, the embryo lives in the womb for several months without attaching to the uterine mucosa. Fertilization of the sable, marten, ermine, badger, and roe deer occurs during the summer-fall period, but accelerated development of the ovum does not begin until the end of winter; hence, gestation in those animals goes on for nine months or more.
(3) In medicine, incubation period; the initial, latent period of a disease, without external manifestation.