E2science

Besides being divided into separate lobes based on function, the material of the cortex has distinct features that are much smaller and more specialized. Two millimeters of cortical (gray) matter sits on top of the white matter, and is actually responsible for all cortical functions. The much more voluminous white matter below does no processing at all -- it's more responsible for transporting oxygen, mollifying damage, and maintaining the blood-brain barrier. Each square millimeter of that cortical surface, however, contains around 148,000 neurons; each is involved with the others in the intense communication that eventually exhibits itself as action, response, and thought.

The cerebral cortex itself, that crucial layer of gray matter, is subdivided into six layers. While these layers are not perfectly defined, there is usually much more crosstalk between neurons in any given layer and neurons in other cortical layers or brain areas. From the six layers, three general subdivisions can be made:

• Layers I, II, and III are the three outermost layers, often called the superficial layers. They read information from one another (and to some extent the thalamus), and send information to all the other layers. Being the outermost layers, they are the most recently developed on the evolutionary time scale. Collecting and collating all of the cortical input and influencing all of its output, these layers might well be considered the seat of thought itself.

• Layer IV is the primary terminus of all information coming from the thalamus, which processes all of the body's state and perceptions for the cortex. This layer also is partially responsible for sending information back to the thalamus, as a check against cortical overstimulation. This layer's contact with layers II and III, along with the direct thalamus input noted above, gives the cerebral cortex all of its knowledge about its surroundings.

• Layer V picks up information from layers I and II and sends it to sub-cortical brain areas, as well as the and body. Some layer V neurons take information from layers II and III and send it to the corpus callosum so it can reach the other half of the cortex. Others collate information from layer VI and some from layer I, and send it to the pons, superior colliculus, and even the spinal cord itself. If layer IV is the inbox, then layer V can be thought of as the outbox, sending the results of cortical processing wherever they need to go.

• Layer VI, finally, takes the information available in itself and layer IV, and sends it to the thalamus. Interactions between these two areas probably allow for conscious control, and to a lesser extent automatic, of what stimuli we are paying attention to, like glancing toward your cat from the computer monitor.

Surprisingly, this variegation is constant over the whole cortical surface, and even more surprisingly has the same configuration in all mammals. What varies between mammals is the cortical surface area and ratio of layers II and III to the entire cortical depth. That is, the surface area of the human cerebral cortex is around 2200 cm², whereas chimpanzees have around 600 cm², cats have 220 cm², and rats have less than 7 cm². More importantly, since percentages don't corelate with animal size, rodents have only around 25% of their cortex depth taken up by level II/III neurons, while carnivores have about 36% and primates 48%. These differences probably arose as evolution created opportunities for animals with ever greater cortical processing power, which is to say, ever more complex thought.

After single neurons, the first level of cortical organization found (in research thus far, at least) is the minicolumn. These are groups of cells between 20 and 65 micrometers in diameter, which cross all six cortical layers in sort of a cylinder shape. Composed of roughly 100 neurons, these are generally separated from one another by 30 micrometers or so. While it is tempting to think of these as "modules," interchangeable on some level, they are each wired differently and each have axons and dendrites that differ both spatially and functionally.

A group of minicolumns together makes up a macrocolumn, which is generally between .4 and 1 millimeters in diameter. Macrocolumns are probably the result of a large neural input to that particular area of the cortex, which during development causes neurons to grow around it. Again, these structures are not functionally interchangeable -- each one is different from all the others. While macrocolumns usually penetrate all six cortical layers, in the visual cortex they only exist in layers I-III, and are known when found in that area as color blobs.

Coconut oil, also known as copha, is an oil extracted from fermented and purified coconut milk. It is made up of over 80 percent saturated fatty acids, the highest out of any plant-based oil. Because of its high amount of saturated fat the oil is actually an opaque solid at room temperature but quickly melts when gently heated. The liquid form of the oil is clear and has a mild, sweet coconut taste. Coconuts and coconut oil have been used in tropical regions worldwide for thousands of years and are still widely used there today. However, areas outside of the tropics rarely use coconut oil. This is partially due to accessibility issues and the presence of stronger markets in corn and soybean oil, but the main reason is because of the belief that all saturated fats are unhealthy.

There are several different kinds of coconut oil. First, the oil is characterized as either commercial grade, also known as “copra”, or premium grade. Copra grade oil is made from dried coconuts and it must be refined over several months to make the oil edible. This refining process involves bleaching and deodorizing the oil and destroys nutrients such as vitamin E and antioxidants naturally present in the coconut flesh. The oil also may be hydrogenated, which can introduce harmful trans fatty acids into the oil. Premium grade oil is made by pressing fresh, higher quality coconuts that are no more than a day old. No chemicals are added to the oil and the entire process takes only several days. Premium grade oil is an unrefined oil and retains the nutrients that are present in the oil. It also tends to be more expensive than the commercial grade. Premium grade coconut oil can also be further divided into virgin or extra virgin oil, much like the classifications of olive oil. Extra virgin oil has the lightest taste, viscosity, and shelf life of the two.

Coconut oil and health concerns

Coconut oil is widely believed to be especially unhealthy because of its high level of saturated fatty acids. This was because of early studies that showed that animals fed coconut oil developed higher levels of cholesterol. However, the animals were fed a hydrogenated form of coconut oil that did not contain any essential fatty acids. The increase in cholesterol levels were actually due to a deficiency in these essential fatty acids or due to the trans fatty acids in the hydrogenated oil. Studies with hydrogenated corn and soybean oil that did not have essential fatty acids showed similar results as the coconut oil, even though the former two oils have minimal levels of saturated fatty acids. Additionally, studies done on populations that consume high amounts of coconut oil do not show higher levels of cholesterol levels or heart disease. These reports indicate that the oil is not as unhealthy as previously believed.

The saturated fatty acids that are present in coconut oil are classified as medium chain fatty acids, which are turned into energy much easier than long chain fatty acids that are found in animal products like meat and butter. Medium chain fatty acids are absorbed from the intestines directly to the liver, while long-chain fatty acids must move from the intestines to the bloodstream before reaching the liver. Additionally, medium chain fatty acids have been shown to not raise cholesterol levels or raise the risk for heart disease. One of the medium chain fatty acids is lauric acid, which makes up 50% of all the fatty acids in coconut oil. The body converts it to monolaurin, a molecule that is also produced in breast milk and is a known antiviral and antibacterial agent.

Uses of coconut oil

Coconut oil is not commonly used in the United States and cannot be found in most grocery stores. Specialty and health food stores may stock the oil and it can also be found online. Refined coconut oil has a surprisingly long shelf life, longer than any other plant oil. This is because it contains only a small amount of monounsaturated and polyunsaturated fatty acids, which are prone to oxidation and spoilage. The antioxidants in coconut oil also help keep it stable. The oil will keep in a dark cabinet at room temperature for about a year and a half, if not longer. Researchers have tested samples of the oil that are several years old that do not show any signs of rancidity.

The oil is used both in cooking and as a moisturizing agent. It can be incorporated into sauces, dips, marinades, and salad dressings. It can also be used to pan fry meats or vegetables and deep fry foods at temperatures below 350 ° F. The oil is often used to moisturize the skin, hair, and scalp and is used as a base for massage oils. Extracts and chemicals derived from coconut oil are common ingredients in shampoos, conditioners, soaps, and lotions.

panamaus states: "You may want to note that coconut oil is widely used in the US by cinemas to pop their popcorn. This is the reason that theatre popcorn tastes so much better than the kind one would make at home. The fat content of popcorn made with this oil is astronomical! Cinemas generally purchase it in 5-gallon drums from companies that supply movie concessions. :)"

http://www.westonaprice.org/know_your_fats/coconut_oil.html
http://www.qualityfirst.on.ca/FAQ%27s.htm
http://www.coconutoilonline.com

(Formerly p_H·, p_H+, P_H, PH) The degree of acidity or alkalinity (basicity or baseness) of a solution. The measurement was introduced as p_H· by Danish biochemist Søren Sørensen in 1909 in Biochemische Zeitschrift, the p representing the German potenz, "power" and the H· representing the hydrogen ion. It is the negative of the common logarithm of the concentration of hydrogen ions (or protons) in moles per litre of solution (pH = -log[H⁺]). For example, the common logarithm of .0000001 (1 × 10^-7) mole of hydrogen ion per litre equals -7, the negative of which is 7. Therefore, 7 is the pH.

The pH of an aqueous solution normally lies between 0 and 14. A pH of 7, the value for pure water, is regarded as neutral. pH values from 7 to 0 indicate increasing acidity and from 7 to 14 indicate increasing alkalinity. A decrease of one unit of pH (an increase in acidity) indicates a tenfold increase in hydrogen ion concentration. An increase of one unit of pH (an increase in alkalinity) indicates a tenfold decrease in hydrogen ion concentration.

Litmus can be used as a pH indicator; it is red in acid solutions and blue in alkaline solutions. A pH meter translates into pH readings the difference in electromotive force between suitable electrodes placed in the solution to be tested.

See also: acid, base, buffer

Water intoxication kills primarily by diluting the blood and causing hyponatraemia (low blood sodium). Water then moves by osmosis from its area of high concentration to its area of low concentration - from the blood to the intracellular space.

The swelling the water causes is called oedema (US - edema), pulmonary oedema in the lungs, cerebral oedema in the brain. Cerebral oedema results in confusion, convulsions, coma and ultimately death.

The figure of 8 gallons/hr is extremely high. The "lethal dose of water" could be very much lower, though I would hesitate to put a figure on it. Leaving wet, dry and secondary drowning aside and considering oral or intravenous fluid, the kidneys of a healthy adult can excrete a maximum of less than 1 litre/hr. This figure may be very much reduced in patients with renal or heart failure in whom fluid balance is notoriously difficult to maintain.

Of course, this does not mean that drinking more than 1 litre/hr will kill you, particularly if you are fluid-depleted. Dehydration is a much more common killer. Homeostasis is quietly effective even in the face of gross physiological insult. Nonetheless, there's a limit.

Drinking large volumes of pure water in a short period, particularly while electrolyte loss is occurring (heavy sweating, bleeding, vomiting, diarrhoea, burns etc.), is dangerous. It remains a major cause of death amongst children worldwide following diarrhoeal illness - though a massive campaign by the UN and WHO has helped. It's what kills people in those inexpressibly stupid water drinking contests. Famously, it's what killed Leah Betts, in whose case excess water consumption was compounded by drug-induced failure of normal homeostasis (see SIADH).

In everyday situations and in normal quantities, pure water is fine for hydration - healthy, readily available and cheap. Dietary sodium intake is almost always more than adequate. When large-volume fluid replacement is required acutely, particularly when electrolytes are being lost (see above), it's advisable to replace salt and sugar as you go, with isotonic rehydration solutions. You can buy these as sports drinks or sachets of oral rehydration salts. Alternatively you can make your own with 8 level teaspoons of sugar and 1 level teaspoon of salt per litre of water. Half a mashed banana adds flavour and potassium.*

Everything2 medical disclaimer

 

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* - http://www.rehydrate.org/solutions/homemade.htm#recipes

Thanks to doyle for advice on a few changes.