WordNet

relating to or being the keynote of a major or minor scale; "tonic harmony"
a medicine that strengthens and invigorates (同)restorative
(music) the first note of a diatonic scale (同)keynote
lime- or lemon-flavored carbonated water containing quinine (同)tonic_water, quinine water
used of syllables; "a tonic syllables carries the main stress in a word" (同)accented
employing variations in pitch to distinguish meanings of otherwise similar words; "Chinese is a tonal language" (同)tonal
of or relating to or producing normal tone or tonus in muscles or tissue; "a tonic reflex"; "tonic muscle contraction"
(physiology) a shortening or tensing of a part or organ (especially of a muscle or muscle fiber) (同)muscular_contraction, muscle_contraction
the act of decreasing (something) in size or volume or quantity or scope
a word formed from two or more words by omitting or combining some sounds; "`wont is a contraction of `will not"; "`oclock is a contraction of `of the clock"

PrepTutorEJDIC

強壮剤;養毛剤,ヘアトニック / (精神的に)元気付けるもの / =tonic water / 主音(音階の中心となる第1音) / 強壮にする,元気付ける / 音調の / (音楽で)主音の
〈U〉〈C〉(…の)収縮,短縮《+『of』+『名』》 / 〈U〉(通貨・資金・支出などの)縮小,節減《+『of』+『名』》 / 〈U〉(いやなこと・よくないことを)身に負うこと,(悪習などが)身につくこと《+『of』+『名』》 / 〈C〉陣痛
(重量単位の)『トン』 / (容積単位の)トン(物によって異なり,木材では40立方フィート,小麦では20立方フィート) / 《話》大量(の…),多数(の…)《+of+名》

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/03/13 04:40:33」(JST)

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A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction^[1] evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate.^[2]^[3] During this state, a motor unit has been maximally stimulated by its motor neuron and remains that way for some time. This occurs when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency. Each stimulus causes a twitch. If stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches. If stimuli are delivered at high frequency, the twitches will overlap, resulting in tetanic contraction. When tetanized, the contracting tension in the muscle remains constant in a steady state. This is the maximal possible contraction.^[2] During tetanic contractions, muscles can shorten, lengthen or remain constant length.^[4]

Tetanic contraction is usually normal (such as when holding up a heavy box). Muscles often exhibit some level of tetanic activity, leading to muscle tone, in order to maintain posture;^[5] for example, in a crouching position, some muscles require sustained contraction to hold the position. Tetanic contraction can exist in a variety of states, including isotonic and isometric forms—for example, lifting a heavy box off the floor is isotonic, but holding it at the elevated position is isometric.

Voluntary sustained contraction is a normal (physiologic) process (as in the crouching or box-holding examples), but involuntary sustained contraction exists on a spectrum from physiologic to disordered (pathologic). Muscle tone is a healthy form of involuntary sustained partial contraction. In comparison with tetanic contraction in an isometric state (such as holding up a heavy box for several minutes), it differs only in the percentage of motor units participating at any moment and the frequency of neural signals; but the low percentage and low frequency in healthy tone are the key factors defining it as healthy (and not tetanic). Involuntary sustained contraction of a hypertonic type, however, is a pathologic process. On the mild part of the spectrum, cramps, spasms, and even tetany are often temporary and nonsevere. On the moderate to severe parts of the spectrum are dystonia, trismus, pathologic tetanus, and other movement disorders featuring involuntary sustained strong contractions of skeletal muscle.

References

^ "Tetanic". The American Heritage Medical Dictionary. Boston Massachusetts: Houghton Mifflin Company. 2007. p. 815. ISBN 978-0-618-82435-9. Marked by sustained muscle contractions
^ ^a ^b Mann MD (2011). "Chapter 14: Muscle Contraction: Twitch and tetanic contractions". The Nervous System In Action. Michael D. Mann.
^ Lombard JH, Rush NJ (2003). "Cells, Nerves, and Muscles". In Raff H. Physiology Secrets (2nd ed.). Philadelphia, PA: Hanley & Belfus. pp. 25–26. ISBN 978-1-56053-509-6.
^ Widmaier EP, Raff H, Strang KT (2010). "Muscle". Vander's Human Physiology: The Mechanisms of Body Function (12th ed.). New York, NY: McGraw-Hill. pp. 250–291. ISBN 0-321-98122-7.
^ Davidoff RA (1992). "Skeletal muscle tone and the misunderstood stretch reflex". Neurology. 42 (5): 951–63. doi:10.1212/WNL.42.5.951. PMID 1579249.

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