The autonomic nervous system (ANS or visceral nervous system or involuntary nervous system) is the part of the peripheral nervous system that acts as a control system, functioning largely below the level of consciousness, and controls visceral functions. The ANS effects heart rate, digestion, respiratory rate, salivation, perspiration, pupillary dilation, micturition (urination), and sexual arousal. Most autonomous functions are involuntary but a number of ANS actions can work alongside some degree of conscious control. Everyday examples include breathing, swallowing, and sexual arousal, and in some cases functions such as heart rate.
Within the brain, the ANS is located in the medulla oblongata in the lower brainstem. The medulla's major ANS functions include respiration (the respiratory control centre, or "rcc"), cardiac regulation (the cardiac control centre, or "ccc"), vasomotor activity (the vasomotor centre or "vmc"), and certain reflex actions (such as coughing, sneezing, vomiting and swallowing). These then subdivide into other areas and are also linked to ANS subsystems and nervous systems external to the brain. The hypothalamus, just above the brain stem, acts as an integrator for autonomic functions, receiving ANS regulatory input from the limbic system to do so
The ANS is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS) which operate independently in some functions and interact co-operatively in others. In many cases the two have "opposite" actions where one activates a physiological response and the other inhibits it. An older simplification of the sympathetic and parasympathetic nervous systems as "excitory" and "inhibitory" was overturned due to the many exceptions found. A more modern characterisation is that the sympathetic nervous system is a "quick response mobilising system" and the parasympathetic is a "more slowly activated dampening system", but even this has exceptions, such as in sexual arousal and orgasm where both play a role. The enteric nervous system is also sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
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Lead and Human health

Lead is actually a metal that happens naturally within the earth. It has numerous industrial employs and is found in trace amounts everywhere from the human atmosphere.

The quantity of lead within the natural environment increased during the Industrial Revolution, and once again in the 1920s with the introduction of leaded gasoline. However, ranges of lead within the Canadian environment have gone down significantly over the past thirty many years. Current studies have also proven a decline of over 70% in blood lead levels in Canadians due to the fact the 1970s. Nonetheless, you can find measures you can take to even more reduce your exposure.

Lead is often damaging to individuals of all ages. Latest scientific studies display that adverse well being results are taking place at lower ranges of publicity to lead than previously thought. Low-level exposure may have subtle effects about the intellectual growth and behavior of infants and young children. These are particularly vulnerable to the dangerous results of lead due to the fact their developing bodies soak up lead additional very easily and remove it less effectively than adults. Also, infants and younger young children are extra likely to ingest lead due to their regular habit of placing issues in their mouths. In grownups, the strongest scientific evidence to date suggests minimal amounts of lead exposure may possibly trigger a smaller raise in blood strain.

Ongoing publicity to even tiny quantities of lead could inevitably result in dangerous amounts within the physique. When lead is absorbed into your blood, it is both eradicated out of your physique (largely in urine) or builds up inside your bones. It could stay stored with your entire body for above thirty years.

Well being effects connected with exposure to substantial ranges of lead incorporate vomiting, diarrhea, convulsions, coma or even death. Nonetheless, such significant scenarios of lead poisoning are rare in Canada.
07/01/2013 00:40:26
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