The constant low-level activity of a body tissue, especially muscle tone.
- ‘Upper airway patency during sleep is determined, in part, by the tonus of pharyngeal dilator muscles.’
- ‘Also, subjacent vascular smooth muscle cells increase their tonus.’
- ‘Since then, I have always remembered the side effects of fentanyl, particularly the increase in sphincter tonus, and all my junior colleagues hear a ‘short lecture’ from me on the subject.’
- ‘They also reported a decrease in uterine tonus and an increase in fetal movements.’
- ‘Muscle tonus, measured by the EMG, is also often recorded since muscle tonus decreases within sleep.’
Late 19th century: from Latin, from Greek tonos tension.