September 30, 2012

The spark of life by Frances Ashercroft

The spark of life by Frances Ashercroft
Electricity in the Human Body.

[Includes many new information on human body and how things works in human body - esp. poisons work].

Warning : Reader is strongly advised not to try any of the experiments described in the book on themselves or others or on animals. The author and publishers accept no responsibility for any resulting harm if the reader should fail to heed this advice.

There is a fundamental difference between the electricity that powers our bodies and that which lights our cities. The electricity supplied to our homes is carried by electrons. Electrons always flow from a region of negative to positive charge. which means that the current in a wire moves in the opposite direction to that in which the electrons flow. In contrast, almost all currents in the animal kingdom are carried by ions - electrically charged atoms. There are five main ions that carry currents in our bodies. Four are positively charged - sodium, potassium, calcium and hydrogen (protons) and one, chloride is negatively charged.  Because they are electrically charged, the movement of ions creates an electric current. In the case of positively charged ions, the current flow is in the same direction as the flow of ions, whereas for negatively charged ions 9as the electrons) it is in the opposite direction.

[An atom can be an ion, but not all ions are atoms. When an atom's outermost orbital gains or loses electrons (also known as valence electrons), the atom forms an ion. Ions are atoms or molecules that have gained or lost one or more of their valence electrons and have a net positive or negative charge - copied from]

Maintaining the ion gradients is expensive; it is extraordinary to think that about a third of the oxygen we breathe and half of the food we eat is used to maintain the ion concentration gradients across our cell membranes. The brain alone uses about 10 percent of the oxygen you breathe to drive the sodium pump and keep your nerve cell batteries charged.

An ion channel is no more than a tiny protein pore. It has a central hole through which the ions move, and one or more gates that can be opened and closed as required to regulate ion movements. When the gate is open, ions such as sodium and potassium swarm through the pore into or out of the cell, at a rate of over a million ions a second. Conversely. when gate is closed, ion flux is prevented. The very largest ion channels are simply giant holes, so big that many ions can go through at a time and both negatively charged ions (anions) and positively charged ions (cations) can permeate as well as quite large molecules. Such channels are not common as it may cause the cell to die. All those ion concentration gradients that the cell setup and protects so carefully would immediately be dissipated if such a channel were to open, causing the cell to die. Some bacterial toxins kill cells in exactly this way. Most channels are choosy about the ions they allow to pass through their pores (potassium channel only permits potassium ions).

The tetrodotoxin contained in the liver and other tissues of this fish is a potent blocker of the sodium channels found in your nerves and skeletal muscles. It causes numbness and tingling of the lips and mouth within as little as 30 minutes after ingestion; gradually paralysis skeletal muscles and ultimately the respiratory muscles are paralyzed which can be fatal. Fugu is considered great delicacy and unfortunately the first is expensive in more ways than one, as unless it is carefully prepared the flesh can be toxic and every year several people die. Properly prepared, the fish is supposed to cause a very mild intoxication and produce a stimulating, tingling sensation in the mouth. A wide variety of animals contain tetrodotoxin, from reef fish, crabs and starfish to marine flatworms, salamanders, frogs and toads.

Like tetrodotoxin, saxitoxin blocks sodium channels and saxitoxin can be found in some mussels, clams and crabs. Both tetrodotoxin and saxitoxin are molecular mimics and both are also valuable research tools because they block sodium channels rather specifically; leaving most other channels untouched. Saxitoxin was exploited by US agents engaged in covet gov. operations both as a suicide and an assassination agent. It has the advantage that is highly poisonous so that only tiny amounts (which can be easily concealed) are needed and it is faster and more effective than cyanide.

Aconite (aconitine) is colloquially called the Queen of Poisons and it comes from monkshood, a pretty plant with a tall spoke of blue helmet-shaped flowers often grown in gardens. Because the toxin is absorbed through the skin, even picking the plant without wearing gloves may cause symptoms.

Another potent sodium channel opener is batrachotoxin, which is secreted from glands on the backs of the vividly marked yellow and black ‘poison dart’ frogs of South and central America. Like aconitine, there is known antidote for batrachotoxin.

Equally fascinating is grayanotoxin, which also locks sodium channels open. It is produced by some species of rhododendron and becomes concentrated in the honey of bees that feed on the flowers’ nectar.

A vast number of toxins that target sodium channels - far more than interact with other types of ion channel. One Reason for this may be that sodium channels are specialized for fast conduction of nerve and muscle impulses. Block then and your prey will be swiftly paralysed and more easily caught.

Botox is the latest tool in the armory of the cosmetic surgeon and is used by film stars and ordinary people alike to smooth out the wrinkles etched on our face by age. But it is actually a virulent poison called botulinum toxin and in my youth it was far more famous for causing fatal food poisoning. Botulinum toxin is one of the most potent natural poisons known. An amount sufficient to cover the head of a pin is more than enough to kill an adult and is estimated as little as gram would kill a million people.Botulinum toxin acts by preventing muscle contraction. When ingested, it gradually relaxes the respiratory muscles until they stop functioning, causing paralysis and death from asphyxiation. In the last decade or two, however, it was realized that if a minute quantity of the toxin is injected under the skin, it will paralyze the muscles in a highly localized way. The virtue of botox is that it blinds so tightly to its target that it is only slowly washed away and the muscles remain relaxed for many months. But every six months of so, the procedure must be repeated. The downside is that the toxin also blocks contraction of the muscles used in facial expressions such as smiling and thus tends to produce a smooth expressionless sphinx-like stare.

A large number of drugs and poisons work by interfering with the action of acetylcholine at its muscle receptor. The most famous is curare -the poison used by South American Indians to tip their arrows and the darts used in their blowpipes. Curare blocks binding of acetylcholine to its receptors in the muscle membrane and so prevent the nerve from stimulating the muscle fiber. Consequently an animal hit by a dart is completely paralyzed and falls out of the tree to the ground., where it is either slaughtered or dies from respiratory failure. Fortunately curare is poorly absorbed by the digestive system, so animals killed in this way are safe to eat. Curare can be extracted from many different S. American plants, but the best known is the climbing pareira vine Chondrodendron tomentosum. Another substance that inhibits the action of acetylcholinesterase is physostigmine, the active ingredient of the Calabar bean.

Why should chemical transmission be preferred over electrical? One answer is that both its slower speed and the intricacies of its mechanism are better suited where integration of a plethora of signals might be advantageous. Another is that it may simply reflect the way in which cell signalling has evolved. Many simple organisms that consists of single cells, such as bacteria, communicate with one another via chemical messengers, enabling them to act as a vast team with coordinated defensive and attack strategies. large-range chemical messengers known as hormones transmit information between cells in our bodies that lie some distance apart from one another. many different hormones circulate constantly throughout our bodies, influencing our mood, maintaining salt and water balance, stimulating cells to grow, readying our bodies to cope with stressful situation.

Why did the shark attack AT&T fiber-optic cable under the sea? It is presumed that the sharks were attracted by the surrounding electric field, as a shark can sense the tiny electric field caused by normal muscle activity in other organisms and so detect its prey even if it is well camouflaged. A human standing still and immersed in seawater up to their nect will produce an electric field of about 0.12 micro-volts per centimeter for about one meter around the body, which is easily large enough to be sensed by a shark.

The electrical signals produced by heart cells give rise to tiny fluctuations in the electrical potential at the surface of the body that can be picked up by surface electrodes attached to the skin. This is the basis of electrocardiogram (ECG). Nitroglycerin acts by releasing a natural gas called nitric oxide which stimulates the production of a chemical called cyclic GMP that causes blood vessels to relax. Viagra works in a similar way: by elevating cyclic GMP levels in the blood vessels of the penis it causes them to dilate, resulting in an erection.

Pleasure, pain, indeed the evolutionary success of any organism, ourselves included, depends on our ability to perceive the world around us; to see, hear, smell, taste and touch it. Our sense organs convert the myriad signals that constantly bombard us in multiple modalities into a single form that the brain can interpret - electrical energy encoded in our nerve impulses. And in all cases ion channels are needed to transduce sensory information into that electrical signal.

Humans have three cone photopigment whereas most mammals such as dog and cats, have only two cone photopigment and so see only a limited range  of color:contrary to popular belief, bulls do not see red. Other creatures live in a world entirely without color. Mantis shrimp which enjoys ten or more different visual pigments and even tropical fish possess four or five types of cone.

We can discriminate five basic tastes - sweet, salt, sour, bitter and savory (umami). All the many different flavors we taste, however, are really smelt, for these senses work in combination. This explains why your sense is blocked. The ability to identify the correct flavors is also reduced if the food is the wrong color; raspberry juice doesn't taste quite right if it is colored orange or green. Try it, and see if you agree.

Humans have around 350 distinct types of olfactory receptor proteins, although each olfactory neuron carries only a single kind. But we can detect far more than 350 aromas; most people can distinguish many thousands of substances, often in tiny amounts. It is widely believed that humans have a poor sense of smell. One reason for our supposed poor sense of smell is that walk around with noses high in the air, while scenes are at their strongest close to the ground and quickly dissipated by air currently at higher levels. When you smell a rose, the scent is wafted up to your olfactory epithelium, where the many different chemicals that make up the smell bind to their receptors on different sets of olfactory neurons. These impulses pass along the olfactory nerve to a region of the brain known as the olfactory bulb where they hand their signals on to other nerve cells in deeper regions of the brain. One of the these is the limbic systems, which is involved in emotion, which explains why smells can trigger such powerful emotions and memories.

In 1912, Wilbur Scoville calibrated the strength of chillies. On the Scoville scale, the mild bell pepper notches up less than one heat unit, a jalapeno pepper has 2,500 to 5,000 units and famously incendiary Bhut Jolokia well over a million. Capsaicin receptor is the ion channel that sense the chilli effect. Binding of capsaicin opened the pore and stimulated electrical activity in the sensory nerve. The channel was also opened by noxious heat. So the reason chili peppers taste so hot is that they open the same ion channel as high temperature and because brain cannot tell the difference between the two stimuli it interprets them both as heat.

We are programmed to seek pleasure. Food, sex drink, exercise - all produce feelings of enjoyment that drive us to seek more. But our impulse to do is more than hedonism or sheer sensual delight; it is a way of ensuring that our species survives. Dopamine, one of the most crucial neurotransmitters in the brain, is intimately involved in desire and addiction. Pleasurable experiences such as sex, love, and food trigger the release of dopamine in the brain's reward center, which increases nerve cell electrical activity, reinforcing our sensation of pleasure and coercing us to have yet another chocolate or glass of wine - too much in some cases.  many drugs of addiction act by increasing the concentration of dopamine in the nucleus accumbens, thereby producing feelings of euphoria.

Happiness and despair are the two faces of the neurotransmitter serotonin. Serotonin is produced by neurons of the raphe nucleus, whose process ramify throughout the brain. Elevated levels of serotonin are associated with feelings of optimism, contentment and serenity. Too little brings despair, depression, anxiety, apathy, and feelings of inadequacy. One way of increasing your serotonin levels by vigorous exercise, which is why brisk walk or a game of squash helps relieve the blues. Modern antidepressants such as Prozac also act by elevating serotonin concentrations.LSD is one of the most powerful hallucinogens known. It has extraordinary effects on auditory and visual perception, producing a sparkling world in which color, brightness and sounds are intensified, objects morph into strange shapes and wall may breathe.

It is impossible to tell, but what i do know is that understanding how the body uses electricity and how memories are laid down, stored and retrieved by the electrical circuits in our brain will be the key to future success in human life.

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