Tetanic contraction

The amount of tension developed by a muscle fiber during tetanic contraction can be as much as three to four times greater than that of a single muscle twitch. The mechanism involved with this increased strength of contraction involves the concentration of cytosolic calcium. Each time muscle fiber is stimulated by an action potential, Ca++ ions are released from the sarcoplasmic reticulum. However, as soon as the these ions are released, a... 

Within 30 minutes and lasting for perhaps 12 hours, there is intoxication, nausea, vomiting, coma, convulsions, nystagmus, papilledema, depressed reflexes, myoclonic jerks, and tetanic contractions. Permanent optic atrophy may occur. 

Fig. 19. Tension, intensity, and spacing time courses from the rising phase of tetanic contractions in bony fish muscle (from Mok et al., 2005). All changes have been normalized to be 0% in resting muscle and 100% at the tetanus plateau for all changes that are increases, and vice versa for all changes that are decreases. (A) Shows the changes of the tension (T), the Al and A2 actin layer lines, and the All (11) equatorial reflection. (B) Shows the M3 spacing and intensity relative to tension (T). (C) Shows the changes of the myosin layer line ML3 and of ML1 at the All and A20 positions. For details, see text.

Adverse reactions In induction of labor, both of these uterotonic agents can cause too frequent contractions, leading to uterine hypertonus, tetanic contractions, fetal distress, and uterine rupture. 

Turkel CC +, Arch Rhys Med Rehabil 87(6), 786 Tetanic contractions... 

Praziquantel stimulates the movement of Hymenolepis and Echinococcus spp. at low concentrations (1 ng/ ml). Higher concentrations of the drug causes rapid contraction of the worms. At a concentration of 1-10 pg/ml of praziquantel, the helminths were found to be immobilized and contracted within 10-30 seconds [26,122,123]. The tetanic contraction of the worm s musculature results in its paralysis. Fetterer and coworkers [124] have shown that the drug is capable of inducing spastic and/or paralytic effects in cestodes, trematodes and to some extent in nematodes also. 

Connolly, R.J., Flow patterns in the capillary bed of rat skeletal muscle at rest and after repetitive tetanic contraction, in Microcirculation, Grayson, J., Zingg, W., Eds., Plenum Press, New York, 1976. 

Hypocalcemia occurring with calcium chelators, magnesium antagonism, or certain loop diuretics may produce muscle spasm and tetanic contractions in most species by increasing cell membrane excitability of motor neurons with resultant increased neuromuscular transmission. Interestingly, flaccid paralysis and recumbency in... 

Tetanic contractions (Wedensky inhibition) induced by repetitive nerve stimulation in phrenic nerve-diaphragm preparations of mice was faded by 0.5-2 ijlM neostigmine (Chang ei al., 1986). The fade was brought about by failure to elicit muscle action potentials, which was due to end-plate depolarization and a decrease in transmitter release. Both effects were attributed to ACh accumulation as a result of ChE inhibition. 

The circumscribed muscular necrosis seen with insecticides has also been seen after sarin4142 and tabun43 administration to experimental animals. Soman produced necrosis in one study,44 but not in another.43 On stimulation of the nerve, the muscle was unable to sustain a tetanic contraction at frequencies of 100 and 200 Hz.43... 

A. Acute poisoning. Nausea and vomiting frequently occur within 30-60 minutes of ingestion. Symptoms of serious intoxication include skeletal muscle weakness, tetanic contractions, respiratory muscle weakness, and respiratory arrest. Laboratory findings include hypocalcemia, hypomagnesemia, and hyperkalemia, and increased QT interval and cardiac dysrhythmias may occur. 

Overdoses of Chinese cimicifuga (standard dose listed as decoction of 3-9 g) may cause nausea, vomiting, and gastroenteritis. High doses have been noted to cause headache, tremors, tetanic contraction of limbs, lassitude, vertigo, and abnormal erections. Extreme overdoses may result in... 

A common clinical problem of the oral or parenteral route of administration of the newer beta-stimulants. such as salbutamol and terbutaline, is digital tremor.This effect is mediated via adrenoceptors of the beta-2 subclass. Incidence of tremor may be as high as 40%. No substantial separation between bronchodilator and tremorogenic activity has been reported.A decrease in the tension and degree of fusion of incomplete tetanic contractions of the slow contracting soleus muscle of the cat is used as a laboratory model predictive of tremor in ntan. ... 

If an adequate stimulus is repeatedly applied to a motor unit at a rate rapid enough for each succeeding stimulus to reactivate the contractile elements before the previous force has completely subsided, successive responses summate, each building upon the previous one until a maximal level is achieved (Figure 24.9b). If the stimulation continues, the contraction peak is maintained at this level. Such a response is known as the tetanus or tetanic contraction. When the stimulation ceases, the contraction terminates, and the fiber relaxes, with the force subsiding quickly to zero. 

FIGURE 24.9 The recruitment curve (a) for the lateral gastrocnemius muscle in a cat when stimulated with intramuscular electrodes (vmpublished works of the authors). The force is normalized to the maximum (tetanic contraction) when the stimulation rate changes (b). 

Making an account of the chemical reactions by the enthalpy balance approach during the contraction-relaxation cycle failed to explain all the sources of the heat [67]. In frog sartorius muscle, for instance, the unexplained heat was 21% of the total produced during isometric tetanic contractions at 0 [68] (see... 

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