Muscle contraction slow onset

Contraction of smooth muscle is significantly slower than that of skeletal muscle. Furthermore, smooth muscle contraction is quite prolonged (3000 msec) compared to that in skeletal muscle (100 msec). The slow onset of contraction as well as its sustained nature is due to the slowness of attachment and detachment of the myosin crossbridges with the actin. Two factors are involved ... 

Dantrolene is a drug that causes spastic muscle contraction. Unlike other muscle relaxants, it has a direct effect on the contractile mechanism by interfering in the process of calcium ion release from the sarcoplasmic reticulum. This results in a lack of coordination in the mechanism of excitation—contraction of skeletal muscle, which has a greater effect on fast muscle fibers than on slow muscle fibers. Dantrolene is used for controlling the onset of clinical spasticity resulting from serious clinical cases such as wounds, paralysis, cerebral palsy, and disseminated sclerosis. Synonyms of this drug are dantrium and danlen. 

Botulinum Toxins. Other neurotoxins, such as the botulinum toxins, must enter nerve terminals before they can block the release of neurotransmitters, which normally cause muscle contraction. These large-protein neurotoxins generally kill by relatively slow onset respiratory failure (within hours to days). The intoxicated individual may not show... 

This slow onset of angiotensin action is associated with a slow offset of its action. When, after the full development of the contraction, the perfusion fluid containing the peptide is changed for fresh solution, relaxation of the smooth muscle occurs very slowly. We have observed that this relaxation can be accelerated by serum containing angiotensinase which, as described by Khairal-... 

In its initial phase acute lead poisoning is associated with anorexia, dyspepsia, and constipation followed by diffuse paroxysmal abdominal pain. The skin is usually pale, the pulse is slow, and blood pressure may increase probably due to spasmodic contraction of smooth muscle. Lead exposure may cause encephalopathy, particularly in children. The Pb-B levels associated with acute encephalopathy onset at 4 xmol/liter with symptoms such as delirium and seizures, in severe cases associated with papilledema [7]. In children the initial symptoms may include vomiting, apathy, stupor, and ataxia. Lead encephalopathy may leave children with persistent neurological and psychological impairment. The alkyl lead species are highly toxic to the central nervous system [2]. 

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