Nerve and muscle systems

Both the G- and V-agents have the same physiological action on humans. They are potent inhibitors of the enzyme acetylcholinesterase (AChE), which is required for the function of many nerves and muscles in nearly every multicellular animal. Normally, AChE prevents the accumulation of acetylcholine after its release in the nervous system. Acetylcholine plays a vital role in stimulating voluntary muscles and nerve endings of the autonomic nervous system and many structures within the CNS. Thus, nerve agents that are cholinesterase inhibitors permit acetylcholine to accumulate at those sites, mimicking the effects of a massive release of acetylcholine. The major effects will be on skeletal muscles, parasympathetic end organs, and the CNS. 

Where accumulation of citrate does occur, this may well react with calcium ions and cause consequent physiological disturbance in nerve and muscle. In this connexion it is interesting to note that fluoroacetate is relatively non-phytotoxic (for its use as systemic insecticide, see p. 182). 

Potassium channels are part of a complex system that helps maintain the normal ionic balance across the cell membrane. In excitable cells, like those in nerves and muscles, the channels also help reestablish the electrical difference between the inside and outside of the cells after excitation. In the case of neuron firing, potassium ions, and thus positive charge, builds up inside the... 

In terms of mineral content, potato is best known as an important source of dietary potassium, which plays a fundamental role in acid-base regulation and fluid balance and is required for optimal functioning of the heart, kidneys, muscles, nerves, and digestive systems. Health benefits of sufficient potassium intake include reduced risk of hypokalemia, osteoporosis, high blood pressure, stroke, inflammatory bowel disease (IBD), kidney stones, and asthma. A high intake of potassium and low intake of sodium have been hypothesized to reduce the risk of stroke (Larsson et al., 2008 Swain et al., 2008). However, most American women 31-50 years old consume no more than half of the recommended amoimt of potassium and men s intake is only moderately higher (lOM, 2004). 

Box 30A) The patient s immune system mistook the acetylcholine receptors at the junction of nerve and muscle cells as a foreign body. Antibodies against these receptors are manufactured and these block the signal transmission between neurons and muscle cells. 

Acetylcholine is a neurotransmitter that functions in conveying nerve impulses across synaptic clefts within the central and autonomic nervous systems and at junctures of nerves and muscles. Following transmission of an impulse across the synapse by the release of acetylcholine, acetylcholinesterase is released into the synaptic cleft. This enzyme hydrolyzes acetylcholine to choline and acetate and transmission of the nerve impulse is terminated. The inhibition of acetylcholineasterase results in prolonged, uncoordinated nerve or muscle stimulation. Organophosphorus and carbamate pesticides (Chapter 5) along with some nerve gases (i.e., sarin) elicit toxicity via this mechanism. 

Little is known about the nervous systems of cestodes and trematodes except that they probably differ from those of nematodes, since milbemycins and avermectins have no effect on them. However, a highly effective anti schistosomal and antitapeworm agent, praziquantel (see Chapter 54 Clinical Pharmacology of the Anthelmintic Drugs), is known to enhance Ca2+ influx and induce muscular contraction in those parasites, though it exerts no action on nematodes or insects. Some benzodiazepine derivatives have activities similar to those of praziquantel these activities are unrelated to the anxiolytic activities in the mammalian central nervous system. The nerves and muscles in schistosomes and tapeworms are thus interesting subjects for future chemotherapeutic studies. 

Experiments on the effects of autonomous and imposed electric fields in biomorphogenesis have been done on many systems including seaweed eggs, plant roots, nerve and muscle in culture, Cecropia oocyte-nurse cell cyncytae, amphibian and rodent limb regeneration and wound healing and regeneration in man (8, 28, 5k). It is clear from these experiments that a... 

The pesticide family most widely used in agricultural and residential applications is the organophosphates, which affect the nervous system by reducing the ability of the enzyme acetylcholinesterase to properly regulate the concentration of the neurotransmitter acetylcholine. If acetylcholine accumulates, the nerve impulses or neurons remain active longer than usual, overstimulating the nerves and muscles and causing symptoms such as weakness or muscle paralysis and death [112]. 

The main action of physostigmine is on the parasympathetic nervous system. It is now known (52, 53) that physostigmine produces its effect by inhibition of the enzyme acetylcholinesterase. The role played by acetylcholinesterase in the transmission of nerve impulses at nerve endings (54, 55) and in the conduction of impulses along nerve and muscle fibers (56, 55) has been described in detail elsewhere. 

The alkali metal ions are very important for the proper functioning of biological systems, such as nerves and muscles Na+ and K+ ions are present in all body cells and fluids. In human blood plasma the concentrations are... 

When humans are in good health, the nervous system and musculature work together so smoothly there is little awareness of how efficiently this complicated biochemical machine functions. Neuromuscular diseases include a vast and bewildering array of related and unrelated disorders that have a certain similarity of symptoms in that both nerves and muscles are usually impaired. This term is usually applied to disorders of the motor unit and specifically excludes primary disorders of the central nervous system such as cerebral palsy. 

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