tonus

n. a continuous, slight stretching tension or contraction in muscles when they are at rest. For example, the jaw muscles exhibit tonus when not used for eating or talking. Tonus serves to keep the muscles ready for action. See also tonic.

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Psychology term of the day

February 23rd 2025

Ballet’s disease

a disorder marked by the loss of movements of the eye and pupil while autonomic responses remain normal. The condition is associated with hyperthyroid disorders, such as exophthalmic goiter (see exophthalmos). Also called Ballet’s sign; ophthalmoplegia externa. [Gilbert Ballet (1853–1916), French neurologist]