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Appetite

Appetite

The appetite is the desire to eat food, felt as hunger. Appetite exists in all higher lifeforms, and serves to regulate adequate energy intake to maintain metabolic needs. It is regulated by a close interplay between the digestive tract, adipose tissue and the brain. Decreased desire to eat is termed anorexia, while polyphagia (or "hyperphagia") is increased eating. Dysregulation of appetite contributes to anorexia nervosa and cachexia on one side, and obesity on the other side of the spectrum.

Regulation

The regulation of appetite has been the subject of much research in the last decade. Breakthroughs included the discovery, in 1995, of leptin, a hormone that appeared to provide negative feedback. Later studies showed that appetite regulation is an immensely complex process involving the gastrointestinal tract, many hormones, and both the central and autonomic nervous systems.

Effector

The hypothalamus, a part of the brain, is the main regulatory organ for appetite. The neurones that regulate appetite appear to be mainly serotonergic, although neuropeptide Y (NPY) and Agouti-related peptide (AGRP) also play a vital role. Hypothalamocortical and hypothalamolimbic projections contribute to the awareness of hunger, and the somatic processes controlled by the hypothalamus include vagal tone (the activity of the parasympathic autonomic nervous system), stimulation of the thyroid (thyroxine regulates the metabolic rate), the hypothalamic-pituitary-adrenal axis and a large amount of other mechanisms.

Sensor

The hypothalamus senses external stimuli mainly through a number of hormones such as leptin, ghrelin, PYY 3-36, orexin and cholecystokinin; all modify the hypothalamic response. They are produced by the digestive tract and by adipose tissue (leptin). Systemic mediators, such as tumor necrosis factor alpha (TNFα), interleukins 1 and 6 and corticotropin-releasing hormone (CRH) influence appetite negatively; this mechanism explains why ill people often eat less. In addition, the biological clock (which is regulated by the hypothalamus) modifies hunger. Processes from other cerebral loci, such as from the limbic system and the cerebral cortex, project on the hypothalamus and modify appetite. This explains why in clinical depression and stress, energy intake can change quite drastically.

Role in disease

A limited or excessive appetite is not necessarily pathological. Abnormal appetite could be defined as eating habits causing malnutrition on the one site or obesity and its related problems on the other. Both genetic and environmental factors may regulate appetite, and abnormalities in either may lead to abnormal appetite. Poor appetite (anorexia) may have numerous causes, but may be a result of physical (infectious, autoimmune or malignant disease) or psychological (stress, mental disorders) factors. Likely, hyperphagia (excessive eating) may be a result of hormonal imbalances, mental disorders (e.g. depression) and others. Dysregulation of appetite lies at the root of anorexia nervosa, bulimia nervosa and binge eating disorder. In addition, decreased response to satiety may promote development of obesity. Various hereditary forms of obesity have been traced to defects in hypothalamic signalling (such as the leptin receptor and the MSH-4 receptor), or are still awaiting characterisation (Prader-Willi syndrome).

Pharmacology

Mechanisms controlling appetite are a potential target for weight loss drugs. Early anorectics were fenfluramine and phentermine. A more recent addition is sibutramine (Reductil®, Meridia®), which increases serotonin and noradrenaline levels in the central nervous system. In addition, recent reports on recombinant PYY 3-36 suggest that this agent may contribute to weight loss by suppressing appetite. Given the epidemic proportions of obesity in the Western world, developments in this area are expected to snowball in the near future, as dieting alone is ineffective in most obese adults.

Further reading


- Neary NM, Goldstone AP, Bloom SR. Appetite regulation: from the gut to the hypothalamus. Clin Endocrinol (Oxford) 2004;60:153-60. PMID 14725674.
- Wynne K, Stanley S, Bloom S. The gut and regulation of body weight. J Clin Endocrinol Metab 2004;89:2576–82. PMID 15181026. Category:Endocrinology Category:Food and drink ja:食欲

Desire

Desire can refer to:
- Desire (album), a Bob Dylan album.
- Desire (DC Comics) of one of the Endless in Neil Gaiman's The Sandman comic series.
- a feeling of interpersonal attraction.
- preference, on which microeconomic theory is based.
- motivation, thought that leads to an action.
- the concept in Lacanian psychoanalytic theory, related to the Oedipus complex.
- tanha in Buddhist psychology, as described in the Four Noble Truths.
- Desire (song) by U2 on the Rattle and Hum album/soundtrack.
- The name of the sailing ship whose crew first discovered the Falkland Islands. ja:欲

Food

Food is any substance that can be consumed, including liquid drinks. Food is the main source of energy and of nutrition for animals, and is usually of animal or plant origin. The study of food is called food science. In English, the term food is often used metaphorically or figuratively, as in food for thought. Food can also be a system of communication, a collection of images, a protocol of usages, situations, and behavior. Food is what brings the memory of our past into our contemporary life.

Legal definition

Western food law defines four categories of object as food:
- any substance or product, whether processed, partially processed or unprocessed, intended to be, or reasonably expected to be ingested by humans whether of nutritional value or not;
- water and other drinks;
- chewing gum;
- articles and substances used as an ingredient or component in the preparation of food. Links to official legal definitions of food:
- [http://www.fda.gov/opacom/laws/fdcact/fdcact1.htm US federal definition of food]
- [http://www.legislation.hmso.gov.uk/acts/acts1990/Ukpga_19900016_en_2.htm#mdiv1 UK definition of food]
- [http://europa.eu.int/smartapi/cgi/sga_doc?smartapi!celexapi!prod!CELEXnumdoc&lg=EN&numdoc=32002R0178&model=guichett EU definition of food]

Human eating habits

Historical development

Humans are commonly believed to be omnivorous animals that can consume both plant and animal products. Evidence suggests that early Homo Sapiens employed Hunter-gatherer as their primary means of food collection. This involves combining stationary plant and fungal food sources (such as fruits, grains, roots, and mushrooms) with mobile animals which must be hunted and killed in order to be consumed. Additionally, it is believed that humans have used fire to prepare food prior to eating since their divergence from Homo erectus, possibly even earlier. At least ten thousand years ago, humans developed agriculture, which has Timeline of agriculture and food and altered the kind of food people eat. This has led to a variety of important historical consequences, such as increased [[population]], the development of [[cities, and the wider spread of infectious diseases. The types of food consumed, and the way in which they are prepared has varied widely by time, location, and culture.

Meals

A portion of food or the act of eating a portion of food is considered a meal. Often named and patterned, meals play a role in an important social occasion, such as the celebration of many key cultural and religious festivals. A meal can be used as means for feeding a single individual or shared and eaten simultaneously by two or more people. The number of meals consumed by individuals in a day, their size, composition, when and how they are prepared and eaten varies greatly around the world. This diversity can be attributed to a number of local factors, including climate, ecology, economy, cultural traditions and industrialisation. In societies where the availability of food has risen above subsistence levels and beyond staple foods, meals are also sold pre-prepared for immediate consumption in restaurants and other similar retail premises. Food eaten in smaller quantities between the culturally normative meals is regarded as snack food. :See also: Appetite, Buddhist cuisine, Eucharist, Fast food, Fasting, Gault Millau restaurant guide, Halaal, I-tal, Kashrut, Michelin restaurant guide, Muslim dietary laws, Potluck, Totemism.

Food production or acquisition

Food is traditionally obtained through farming, ranching, and fishing, with hunting, foraging and other methods of subsistence locally important for some populations, but minor for others. In the modern era in developed nations, food supply is increasingly dependent upon agriculture, industrial farming, aquaculture and fish farming techniques. These techniques aim to maximize the amount of food produced while minimizing the cost. The techniques include a reliance on mechanized tools, from the threshing machine and seed drill, to the tractor and combine. Developed tools have been combined with the use of pesticides to promote high crop yields and to combat insects or mammals which reduce yield. More recently, there has been a growing trend towards more Sustainable agricultural practices. This approach - which is partly fuelled by consumer demand - encourages biodiversity, local self-reliance and Organic farming methods. Major influences on food production are international policy, e.g. the World Trade Organization and Common Agricultural Policy, national government policy or law and war. Food for livestock is fodder and traditionally comprises hay or grain. :See also: mariculture, horticulture, agribusiness, gardening. gardening

From plants


- Seeds
  - Cereals from grasses, including barley, maize, oats, rice, rye, and wheat
  - Cereals from non-grasses, including buckwheat, amaranth, and quinoa
  - Legumes, including beans, peas, and lentils
  - Nuts, including coconuts, almonds, and pine nuts
  - Oilseeds, including sesame, sunflower, and hemp
- Vegetables (see also list of vegetables)
  - Root vegetables, including potatoes, cassava, and turnips
  - Leaf vegetables, including amaranth, spinach, and kale
  - Sea vegetables, including dulse, kombu, and dabberlocks
  - Stem vegetables, including bamboo shoots, nopales, and asparagus
  - inflorescence vegetables, including globe artichokes, broccoli, and daylilies
  - Fruit vegetables, including pumpkin, okra, and eggplant
- Fruits (see also list of fruits)
- Herbs and spices (see also list of herbs and spices) list of herbs and spices

From animals


- Dairy products, including milk
- Eggs, including roe and caviar
- Insects, including honey
- Meat, including beef, frogs' legs, goat, horse, kangaroo, lamb, mutton, pork, veal, rodents, human (i.e. cannibalism)
- Offal, including blood
- Poultry, including chicken, turkey, duck, goose, pigeon or dove, ostrich, emu, guinea fowl, pheasant, quail
- Seafood, including finfish such as salmon and tilapia, and shellfish such as mollusks and crustaceans
- Snails
- Game, this includes all animals hunted for food.

From neither animals or plants


- Salt
- Mushrooms, which are a type of fungi
- Seaweed, which is a protist
- Water, including mineral water and spring (water)

Food preparation

spring (water) While some food can be eaten without preparation, many foods undergo some form of preparation for reasons of safety, palatability, or flavor. At the simplest level this may involve washing, cutting, trimming or adding other foods or ingredients, such as spices. It may also involve mixing, heating or cooling, pressure cooking, fermentation, or combination with other food. Most food preparation takes place in a kitchen. The preparation of animal-based food will usually involve slaughter, evisceration, hanging, portioning and rendering. :See also: Barbecue, Eating utensils, Frankfurt kitchen, Hangi, Oven, Microwave oven, Refrigeration, Food preparation utensils.

Food manufacture

Early food processing techniques were limited by the available food preservation, packaging and transportation. Early food processing mainly involved salting, curing, curdling, drying, pickling and smoking. An early processed food product was cheese. During the industrialisation era in the 19th century, food manufacturing arose. This development took advantage of new mass markets and emerging new technology, such as milling, preservation, packaging and labelling and transportation. It brought the advantages of pre-prepared time saving food to the bulk of ordinary people who did not employ domestic servants. At the start of the 21st century, a two-tier structure has arisen, with a few international food processing giants controlling a wide range of well known food brands; with a populous number of small local or national food processing companies. :See also: Best before, Canning, Coloring, Food quality, Snap freezing, Additives, Flavoring, Enzymes, Genetically modified food, Pasteurization, Shelf-life, Ultra-high temperature processing.

Types of manufactured food


- Drinks: beer, juice, soft drink, squash, wine.
- Bread is a staple food for many nations, being made of risen dough of wheat or other cereals.
- Cakes and cookies
- Cheese is a curdled milk product, of which many varieties exist.
- Dessert is a course, usually sweet, and generally served after the main course, e.g. Ice cream.
- French fries, Chips
- Functional food
- Jam and Jelly
- Pasta
- Pie
- Pizza
- Processed meats
- Sandwiches
- Salad
- Sauce
- Sausage

Food trade

Food is now traded on a global basis. The variety and availability of food is no longer restricted by the diversity of locally grown food or the limitations of the local growing season. Between 1961 and 1999 there has been a 400% increase in worldwide food exports. Some countries are now economically dependent on food exports, which in some cases account for over 80% of all exports. In 1994 trade liberalisation began when over 100 countries became signatories to the Uruguay Round of the General Agreement on Tariffs and Trade which included an agreement to reduce subsidies paid to farmers. This is underpinned by the WTO enforcement of agricultural subsidy, tariffs, import quotas and settlement of trade disputes that cannot be bilaterally resolved. Where trade barriers are raised on the disputed grounds of public health and safety, the WTO refer the dispute to the Codex Alimentarius Commission, which was founded in 1962 by the United Nations Food and Agriculture Organization and the World Health Organization.

Food retailing

World Health Organization The sale of surplus food traditionally took place once a week when farmers took their wares on market day, into the local village market place. Here food was sold to grocers for sale in their local shops for purchase by local people. With the onset of industrialisation, and the development of the food processing industry, a wider range of food could be sold and distributed in distant locations. Typically early grocery shops would be counter-based shops, in which purchasers told the shop-keeper what they wanted, so that the shop-keeper could get it for them. In the 20th century supermarkets were born. Supermarkets brought with them a self-service approach to shopping using shopping carts (or Trollies in Commonwealth English) and were able to offer quality food at lower cost, through economies of scale and reduced staffing costs. This was sometimes known as 'pile it high' In the latter part of the 20th century, this has been further revolutionised by the development of vast warehouse sized out-of-town supermarkets, selling an extraordinarily wide range of food from around the world. Unlike food processors, food retailing is a two-tier market in which a small number of very large companies control a large proportion of supermarkets. The supermarket giants wield great purchasing power over farmers and processors, and strong influence over consumers. Nevertheless, in 2000 only 19% of all US consumer expenditure spent on food went to farmers. Recent technological innovations such as point of sale technology - barcodes. This allows ordering of goods and food to be driven by actual sales.

Food sufficiency

Food deprivation leads to malnutrition and ultimately starvation. This is often connected with famine, which involves the absence of food in entire communities. This can have a devastating and widespread effect on human health and mortality. In 2003 it was estimated that each year, 40 million people die of hunger worldwide. Rationing is sometimes used to distribute food in times of shortage, most notably during times of war. Food deprivation is regarded as a deficit need in Maslow's hierarchy of needs and is measured using famine scales.

Food aid

Food aid can benefit people suffering from a shortage of food. Conversely, badly managed food aid can cause problems by disrupting local markets, depressing crop prices and discouraging food production. Its provision, or threatened withdrawal, is sometimes used as a political tool to influence the politics of the destination country. International efforts to distribute food to the neediest countries are co-ordinated by the World Food Programme. :See also: Fair trade, food security.

Food safety

Foodborne illness, commonly called "food poisoning," is caused by bacteria, toxins, viruses and prions. Food poisoning has been recognised as a disease of man since as early as Hippocrates. Murder by food poisoning was used during the Roman Empire. In the Middle Ages all Royal Courts had food tasters. The sale of rancid, contaminated or adulterated food was commonplace until introduction of hygiene, refrigeration, and vermin controls in the 19th century. Discovery of techniques for killing bacteria using heat and other microbiological studies by scientists such as Louis Pasteur contributed to the modern sanitation standards that we enjoy today. This was further underpinned by the work of Justus von Liebig whose work led to the development of modern food storage and food preservation methods. The two most common factors leading to cases of bacterial foodborne illness are cross-contamination of ready-to-eat food from other uncooked foods and improper temperature control. Less commonly, acute adverse reactions can also occur if chemical contamination of food occurs, for example from improper storage, or use of non-food grade soaps and disinfectants. Food can also be adulterated by a very wide range of articles (known as 'foreign bodies') during farming, manufacture, cooking, packaging, distribution or sale. For example, pests (or their feces), hairs, cigarette butts, wood chips, metal shards, plasters etc. It is possible for certain types of food to become contaminated if stored or presented in an unsafe container, such as a ceramic pot with lead-based glaze. Understanding of the causes of food-borne-illnesses and more systematic techniques for their elimination has led to the development of commercial systems such as HACCP which can, if properly implemented, identify and eliminate many, but not all, possible risks. HACCP is well suited to identifying and controlling these potential food safety risks.

Food allergies

Some people have food allergies or sensitivities to foods which are otherwise wholesome to the majority of people. The amount of the food substance required to provoke a reaction in a susceptible individual can be minute. For instance, tiny amounts of food in the air, too minute to be smelled, have been known to provoke lethal reactions in sufficiently sensitive individuals. In theory, any food may provoke a reaction, however, this most commonly involves gluten, corn, shellfish (mollusks), peanuts, and soy. Most patients present with diarrhea after ingesting certain foodstuffs, skin symptoms (rashes), bloating, vomiting and regurgitation. The digestive complaints usually develop within half an hour of ingesting the allergen. Rarely, food allergy can lead to anaphylactic shock: hypotension (low blood pressure) and loss of consciousness. This is a medical emergency. An allergen associated with this type of reaction is peanut, although latex products can induce similar reactions. Initial treatment is with epinephrine (adrenaline), often carried by known patients in the form of an Epi-pen. Food allergy is thought to develop easier in patients with the atopic syndrome, a very common combination of diseases: allergic rhinitis and conjunctivitis, eczema and asthma. The syndrome has a strong inherited component; a family history of these diseases can be indicative of the atopic syndrome.

Dietary habits

Dietary habits play a significant role in the health and mortality of all humans. For example:
- Eating disorders are a group of mental disorders that interfere with normal food consumption. They often affect people with a negative body image;
- 13% of the world's population suffer from Iodine deficiency;
- In 2003 it was estimated that vitamin A deficiency causes blindness in up to 500,000 children each year;
- Vitamin C deficiency results in scurvy;
- Calcium, Vitamin D and Phosphorus are inter-related. The consumption of each may affect the absorption of the others.
- Kwashiorkor and marasmus are childhood disorders caused by lack of dietary protein.
- Obesity, a serious problem in the western world, leads to higher chances of developing heart disease, diabetes, and many other diseases. Concerns about foodborne illness have long influenced diet. Traditionally humans have learned to avoid foods that induce acute illness. Some believe that this is the underlying rationale behind some traditional religious dietary requirements. Additionally, many people choose to forgo food from animal sources to varying degrees; see vegetarianism, veganism, fruitarianism, living foods diet, and raw foodism. The nutrient content of diets in industrialised countries contain more animal fat, sugar, energy, alcohol and less dietary fiber, carbohydrates and antioxidants. Contemporary changes to work, family and exercise patterns, together with concerns about the effect of nutrition and overeating on human health and mortality are all having an effect on traditional eating habits. Physicians and alternative medicine practitioners may recommend changes to diet as part of their recommendations for treatment. More recently, dietary habits have been influenced by the concerns that some people have about the chronic impact on health that arise through the consumption of genetically modified food. Further concerns about the impact of industrial farming on animal welfare, human health and the environment are also having an effect on contemporary human dietary habits. This has led to the emergence of a counterculture with a preference for organic and local food. :See also: Food faddism, Health claims on food labels, list of diets, Slow Food.

Nutrients in food


- Calcium
- Carbohydrate
- Essential amino acids
- Fat
- Iron
- Minerals
- Phytochemicals, including anti-oxidants, enzymes, bio-flavinoids
- Potassium
- Protein
- Sodium
- Starch
- Vitamins
- Water Category:Nutrition Category:Biology

Hunger

Hunger is applied literally to the need or craving for food; it can also be applied metaphorically to cravings of other sorts. It is an extreme of a normal appetite. The term is commonly used more broadly to refer to cases of widespread malnutrition or deprivation among populations, usually due to poverty, political conflicts or instability, or adverse agricultural conditions (famine).

Hunger as a condition

The term hungry is commonly used simply to mean having an appetite or to be ready for a meal. After a long period without food, the mild sensation of hunger associated with being ready for a meal becomes a progressively more severe sensation, until it becomes acutely painful. Prolonged hunger will drive people to eat substances with no nutritional value, such as grass and soil, simply to fill their stomachs (which has an adverse effect on energy balance as energy is still required to digest these substances). Lack of particular nutrients leads to particular medical types of malnutrition. Kwashiorkor and marasmus are prime examples. Eventually, after protracted malnourishment, death will occur through starvation. Sometimes hunger is defined as the condition in which an organism can only use its protein tissue (e.g. muscles) as the source of energy, a condition which sets in after all sugars and fats etc. are used up. In contrast to hunger, which is involuntary, fasting is the practice of voluntarily not eating for a period of time. A hunger strike is fasting for the purpose of nonviolent resistance.

Politics of hunger

nonviolent resistance As of 2005, hunger continues to be a worldwide problem. According to the Food and Agriculture Organization of the United Nations, "850 million people worldwide were undernourished in 1999 to 2005, the most recent years for which figures are available" and the number of hungry people has recently been increasing. An orange awareness ribbon is used to raise awareness of hunger in the world.[http://www.un.org/Pubs/chronicle/2003/issue4/0403p66.asp] There is a wide range of opinions as to why this problem is so persistent. Organizations such as Food First raise the issue of food sovereignty and claim that every country on earth (with the possible minor exceptions of some city-states) has sufficient agricultural capacity to feed its own people, but that the "free trade" economic order associated with such institutions as the International Monetary Fund (IMF) and the World Bank prevent this from happening. At the other end of the spectrum, the World Bank itself claims to be part of the solution to hunger, claiming that the best way for countries to succeed in breaking the cycle of poverty and hunger is to build export-led economies that will give them the financial means to buy foodstuffs on the world market. Amartya Sen won his 1998 Nobel Prize in part for his work in demonstrating that hunger in modern times was not typically the product of a lack of food; rather, hunger usually arose from problems in food distribution networks or from governmental policies in the developing world.

Hunger in the world

Number of undernourished people (million) in 2000-2002, according to the FAO, the following countries had more than 5 million undernourished people:

See also


- Copenhagen Consensus
- United Nations World Food Programme

External links


- [http://www.wfp.org/country_brief/hunger_map/map/hungermap_popup/map_popup.html World Hunger Map] (from United Nations World Food Programme)
- [http://www.insightnewstv.com/hunger Living with Hunger] (documentary)
- [http://www.thehungersite.com/ The hunger site]
- [http://www.fighthunger.org/ FightHunger.org] -- U.N. World Food Programme's global campaign to end child hunger by 2015
- [http://www.fao.org/es/esn/nutrition/profiles_by_country_en.stm FAO country statistics]
- [http://www.freefromhunger.org/ Freedom from Hunger]
- [http://www.borgenproject.org/ The Borgen Project] Category:Humanitarian aid Category:Food and drink simple:Hunger



Adipose tissue

Adipose tissue is an anatomical term for loose connective tissue composed of adipocytes. Its main role is to store energy in the form of fat, although it also cushions and insulates the body. It has an important endocrine function in producing recently-discovered hormones such as leptin, resistin and TNFα.

Anatomical features

Adipose tissue is primarily located beneath the skin, but is also found around internal organs. In the skin, it accumulates in the deepest level, the subcutaneous layer, providing insulation from heat and cold. Around organs, it provides protective padding. It also functions as a reserve of nutrients. In a severely obese person, excess adipose tissue hanging downward from the abdomen is referred to as a panniculus (or pannus). A panniculus complicates surgery of the morbidly obese, and may remain as a literal "apron of skin" if a severely obese person loses most of the excess weight (as after a bypass). Adipose tissue has an "intracellular matrix," rather than an extracellular one. Adipose tissue is divided into lobes by small blood vessels. The cells of this layer are adipocytes.

Physiology

Free fatty acid is "liberated" from lipoproteins by lipoprotein lipase (LPL) and enters the adipocyte, where it is reassembled into triglycerides by esterising it onto glycerol. Fat cells have an important physiological role in maintaining triglyceride and free fatty acid levels, as well as determining insulin resistance. Abdominal fat has a different metabolic profile—being more prone to induce insulin resistance. This explains to a large degree why central obesity is a marker of impaired glucose tolerance and is an independent risk factor for cardiovascular disease (even in the absence of diabetes mellitus and hypertension). Recent advances in biotechnology have allowed for the harvesting of adult stem cells from adipose tissue, allowing stimulation of tissue regrowth using a patient's own cells. The use of a patient's own cells reduces the chance of tissue rejection and avoids the social trauma associated with the use of human embryonic stem cells. Hormones secreted by adipose tissue include:
- Adiponectin
- Resistin
- Angiotensin
- Plasminogen activator inhibitor-1 (PAI-1)
- TNFα
- IL-6
- Leptin A specialised form of adipose tissue in human infants, and some animals, is brown fat or brown adipose tissue. It is located mainly around the neck and large blood vessels of the thorax. This specialised tissue can generate heat by "uncoupling" the respiratory chain of oxidative phosphorylation within mitochondria, leading to the breakdown of fatty acids. This thermogenic process may be vital in neonates exposed to the cold, who then require this thermogenesis to keep warm as they are unable to shiver, or take other actions to keep themselves warm. Attempts to stimulate this process pharmacologically have so far been unsuccessful, but might in the future be a target of weight loss therapy.

Cultural and social role

In the modern world, excess fatty tissue on a human can lead to medical problems. However, a round or large figure does not of itself imply a medical problem, and is sometimes not primarily caused by adipose tissue. For a discussion of the aesthetic and medical significance of body shape, see dieting and obesity). Adipose tissue, because of its association with high food energy intake and low physical exertion, historically was considered an indication of wealth and privilege.

See also


- Obesity
- Cellulite Category:Tissues Category:Obesity ja:脂肪組織

Brain

In the anatomy of animals, the brain, or encephalon (Greek for "in the head"), is the higher, supervisory center of the nervous system. The term 'brain' is typically used in connection with vertebrate nervous systems, and less often with regard to the nervous system of invertebrates. In the latter, neural control is performed by collections of ganglia. The brain is an extremely complex organ: the human brain is a collection of 100 billion neurons, each linked with up to 25,000 others. This huge number of interconnecting neurons, often referred to as a neural ensemble, is what makes the brain intelligent—enabling humans to analyze sensory signals, control the body, and think. In most animals, the brain is located in the head, close to the primary sensory apparatus and the mouth. Hippocrates considered the brain to be the seat of thought, while Aristotle believed it to be a cooling system for the blood. Today the study of the mind and brain consists of Neuroscience, the field of biology that studies the brain at its various levels of organization (from single neurons to functional systems such as visual system, auditory system, motor system and others); and psychology, the study of the cognition that arises from the neural function of the brain. Attempts have also been made to directly "read" the brain, which has been accomplished in a rudimentary manner through a brain-computer interface. In recent years, several institutions and bodies have undertaken research on recreating the neural structure of the brain with aim to produce human-like cognition and intelligence in computers. The brain controls and coordinates most movement, behavior and homeostatic body functions (such as heartbeat, blood pressure, fluid balance and body temperature). The brain is responsible for cognition, emotion, memory, motor learning and other kinds of learning. However, many behaviors, such as simple reflexes and basic locomotion, can be executed under spinal cord control alone.

The importance of the brain

The brain in animals

Three groups of animals, with some exceptions, have notably complex brains: the arthropods (insects and crustaceans), the cephalopods (octopuses, squid, and similar mollusks), and the craniates (vertebrates and their cousins). The brain of arthropods and cephalopods arises from twin parallel nerve cords that extend through the body of the animal. In arthropod, the brain consists of a central brain with three divisions and large optical lobes behind each eye for visual processing. eye The brain of craniates develops from the anterior section of a single dorsal nerve cord, which later becomes the spinal cord. In craniates, the brain is protected by the bones of the skull. In vertebrates, increasing complexity in the cerebral cortex correlates with height on the phylogenetic and evolutionary tree. Primitive vertebrates, like fish, reptiles, and amphibians have cortices with fewer than six layers of neurons, a structure known as allocortex (also named heterotypic cortex) (Martin, 1996). More complex vertebrates such as mammals have developed a six-layered neocortex (other terms: homotypic cortex, neocortex, neopallium), in addition to having some parts of the brain that are allocortex (Martin, 1996). In mammals, increasing convolutions of the brain, called gyri, are characteristic of animals with more advanced brains. These convolutions evolved to provide a larger surface area for a greater number of neurons, while keeping the volume of the brain compact enough to fit inside the skull.

The human brain

The structure of the human brain is different from that of other animals in several significant ways. These differences have allowed for many abilities over and above those of other animals, such as advanced cognitive skills. Human encephalization is especially pronounced in the neocortex, the most complex part of the cerebral cortex. The proportion of the human brain that is devoted to the neocortex—and the most advanced part within it, the prefrontal cortex—is larger than in all other animals. Humans enjoy unique neural capacities, but much of the human neuroarchitecture is shared with ancient species. Basic systems that alert the nervous system to stimulus, that sense events in the environment, and that monitor the condition of the body are similar to those of the most basic vertebrates. The neural circuitry underlying human consciousness includes both the advanced neocortex and protypical structures of the brain stem. The human brain also has a a million billion synaptic connections, making it one of the most densely connected network systems in the known universe; however, more complex structures may exist.

Pathology of the brain

The loss of function in the brain fulfills some definitions of death. Injuries to the brain tend to affect large areas of the organ, sometimes causing major deficits in intelligence, memory and control of the body. Head trauma, caused, for example, by vehicle and industrial accidents, is a leading cause of death in youth and middle age. In these cases, more damage is typically caused by resultant swelling (edema) than by the impact itself. Stroke, caused by the blockage of blood vessels in the brain, is another major cause of death from brain damage. Other problems in the brain can be more accurately classified as diseases rather than injuries. Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, motor neurone disease, and Huntington's disease, are caused by the gradual death of individual neurons, leading to decrements in movement control, memory, and cognition. Currently, only the symptoms of these diseases can be treated, but stem cell research may offer a cure. Mental illness, such as clinical depression, schizophrenia, bipolar disorder, and post-traumatic stress disorder, are brain diseases that impact on the personality and typically on other aspects of mental and somatic function. These disorders may be treated by psychiatric therapy, by pharmaceutical intervention, or by a combination of treatments; therapeutic effectiveness varies significantly among individuals. pharmaceutical Some infectious diseases affecting the brain are caused by viral and bacterial infection(s). Infection of the meninges, the membrane that covers the brain, can lead to meningitis. Bovine spongiform encephalopathy (also known as mad cow disease), is deadly in cattle and is linked to prions. Kuru is a similar prion-borne degenerative brain disease affecting humans. Both are linked to the ingestion of neural tissue, and may be an evolutionary defense against cannibalism. Viral or bacterial causes have been substantiated in multiple sclerosis, Parkinson's disease, Lyme disease, encephalopathy and encephalomyelitis. Some brain disorders are congenital. Tay-Sachs disease, Fragile X syndrome, Down syndrome, and Tourette syndrome are all linked to genetic and chromosomal errors. Malfunctions in the embryonic development of the brain can be caused by genetic factors, by drug use, and disease during a mother's pregnancy.

Other matters

Some philosophers consider that "brain" is synonymous with "mind", while others (such as strong AI theorists) believe that the mind is analogous to software and the brain to hardware. This issue—related to the mind-body problem—and many other issues, are the subjects of the area of the philosophy of mind. Questions asked in this field typically relate to the nature of consciousness and whether non-human animals are conscious beings. Computer scientists have produced computer systems called neural networks, loosely based on the structure of neuron connections in the brain. Artificial intelligence seeks to replicate brain function—although not necessarily brain mechanisms—but as yet is an immature science. Creating algorithms to mimic a biological brain is extremely difficult because the brain is not a static arrangement of circuits, but a network of vastly interconnected neurons that are constantly changing their connectivity and sensitivity. More recent work in both neuroscience and artificial intelligence models the brain using the mathematical tools of chaos theory and dynamical systems. Brain activity can be detected by electrodes, raising the possibility of "brain-computer interface". The reverse path has been demonstrated: brain implants have been used to generate artificial hearing and (crude and experimental) artificial vision for deaf and blind people; brain pacemakers are now commonly used to regulate brain activity in conditions such as Parkinson's disease. Both of these avenues of research are confronted with potentially serious ethical implications. For example, by placing electrodes in the brain and using a remote control, researchers have been able to remotely control the movements of a rat, combining commands of what to do with the stimulation of the brain pleasure centers. This raises the possibility of creating an electronically controlled biological "ratbot" that could be used in dangerous circumstances.

The biology of the brain

Despite the variance of the species in which the brain is found there are many common features in its cellular make-up, its structure and its function. On a cellular level, the brain is composed of two classes of cell, neurons and glia, both of which contain several different cell types which perform different functions. Interconnected neurons form neural networks (or neural ensembles). These networks are similar to man-made electrical circuits in that they contain circuit elements (neurons) connected by biological wires (nerve fibers). Of course, these do not form simple one-to-one electrical circuits (as is the case in many man-made circuits), neurons typically connect to at least a thousand other neurons. These highly specialized circuits make up systems which are the basis of perception, action and higher cognitive function. The brain contains anatomical and functional divides. In mammals, the most obvious partitioning of the brain is into the cerebrum (Latin for "brain", a large, anterior part that consists of two convoluted hemispheres and deep nuclei), cerebellum (Latin for "small brain", a smaller, structure behind the cerebrum with two rippled hemispheres and deep cerebellar nuclei), and brain stem (an elongated structure connecting the brain to the spinal cord). These parts are further divided into hemispheres, lobes, gyri, cortices, cytoarchitectonic and functional areas, nuclei, layers, fiber tracks and so forth. In summary, the chemical and electrical impulses continually passing through the cells of the brain produce all control, action and cognitive function in the body.

Histology

lobe Neurons, the cells that generate action potentials and convey them to other cells, constitute the chief class of brain cells. In each particular brain area, input (or afferent) neurons, output (or efferent) neurons and interneurons are typically found. Input neurons are recipients of projections from other brain areas. Output neurons project to the other areas. Interneurons are the neurons which do not leave the area. In addition to neurons, the brain contains glial cells in the proportion roughly 10 glial cells to every neuron; these are traditionally seen to perform supportive roles to neurons and fill out the space between them (hence its name, Greek for 'glue'). Most types of glia in the brain (and the rest of the central nervous system) are present in the entire nervous system, exceptions include oligodendrocytes which insulate neural axons (a role performed by Schwann cells in the peripheral nervous system). Oligosaccharides are the defining factor between white matter and grey matter in the brain—white matter is composed of myelinated (insulated) axons, whereas grey matter contains mostly cell soma, dendrites and unmyelinated portions of axons and glia and a smaller proportion of myelinated axons. In mammals, the brain also contains a certain amount of connective tissue called the meninges which is a system of membranes that separate the skull from the brain. The three-layered covering is made of, from the outside in, dura mater, arachnoid and pia mater (the latter two are connected and thus often considered as a single layer, the pia-arachnoid). Below the arachnoid is the subarachnoid space which contains cerebrospinal fluid which protects the nervous system. Blood vessels enter the central nervous system through the perivascular space above the pia mater. A blood-brain barrier protects the brain from unwanted substances that might enter it through the blood. The brain is suspended in cerebrospinal fluid, which circulates between layers of the meninges and through cavities in the brain called ventricles. It is important both chemically (metabolism) and mechanically (shock-prevention).

Anatomy

Although the histology of the brain is common to all those who have one, the structural anatomy is not. Apart from the general nature of the brain to order into lobes and suchforth, the lobes into which it has evolved are not common across the vertebrate/invertebrate divide. There are further dissimilarities within invertebrates, though vertebrates tend to share certain commonalities.

Invertebrates

In insects, the brain can be divided into four parts, the optical lobes, the protocerebrum, the deutocerebrum, and the tritocerebrum. The optical lobes are positioned behind each eye and process visual stimuli (Butler, 2000). The protocerebrum contains the mushroom bodies, which respond to smell, and the central body complex. The deutocerebrum includes the antennal lobes, which are similar to the mammalian olfactory bulb, and the mechanosensory neuropils which receive information from touch receptors on the head and antennae. The antennal lobes of flies and moths are quite complex. In cephalopods, the brain is divided into two regions: the supraesophageal mass and the subesophageal mass. These parts are divided by the animal's esophagus. The supra- and subesophageal masses are connected to each other on either side of the esophagus by the basal lobes and the dorsal magnocellular lobes. The large optic lobes are sometimes not considered to be part of the brain proper since the optic lobes anatomically separate from the brain and are joined to the brain by the optic stalks. However, the optic lobes perform much of the visual processing and can be functionally considered to be a part of the brain.

Vertebrates

In vertebrates, a gross division into three major parts is used: hindbrain (medulla oblongata and metencephalon), midbrain (mesencephalon) and forebrain (diencephalon and telencephalon). Varied taxonomies have been used by assorted schools at various times in history for the study of diverse species. An anterior part of the telencephalon called the cerebrum makes up the largest section of the mammalian brain and in humans, its surface has many deep fissures (sulci) and convolutions (gyri), giving a wrinkled appearance to the brain. In most vertebrates the metencephalon is the highest integration center in the brain, whereas in mammals this role has been adopted by the cerebrum. Behind (or in humans, below) the cerebrum is the cerebellum, a convoluted structure whose neural circuitry is often compared with crystal structure. Cerebellum participates in the control of movement. The cerebellum attaches to the hindbrain in a structure called the pons. The cerebrum and the cerebellum consist each of two halves (hemispheres). The corpus callosum connects the two hemispheres of the cerebrum. An outgrowth of the telencephalon called the olfactory bulb is a major structure in many animals, but in humans and other primates, it is relatively small. Vertebrate nervous systems are distinguished by encephalization and bilateral symmetry. Encephalization refers to the tendency for more complex organisms to gain a larger-size brains through evolutionary time. Larger vertebrates develop a complex of layered, networked and convoluted grey matter and white matter. Grey matter refers to tissue mostly comprised of neurons and can be found on the surface of cerebral cortex, as well as in clusters called nuclei deep within the brain. White matter refers to axons and their surrounding myelin insulation, which gives this tissue its white color. White matter is found in bundles of fibers known as tracts which connect the different parts of the brain. In modern species most closely related to the first vertebrates, brains are covered with gray matter that has a three-layer structure. Their brains also contain deep brain nucleus and fiber tracks forming the white matter. Most regions of the human cerebral cortex have six layers of neurons, a structure known as neocortex.

Brain Regions in Vertebrates

According to the hierarchy based on embryonic and evolutionary development, chordate brains are composed of the following regions:
- RHOMBENCEPHALON (Greek for "rhomboid brain")
  - Myelencephalon (Greek for "brain marrow", also called medulla oblongata which means "long marrow" in Latin)
  - Metencephalon (Greek for "after the brain"; also called hindbrain)
    - pons
    - cerebellum
- MESENCEPHALON (Greek for "middle brain", also called midbrain)
  - tectum
  - midbrain tegmentum
  - substantia nigra
  - crus cerebri (also called cerebral peduncles and pedunculus cerebri)
- PROSENCEPHALON
  - Diencephalon (Greek for "brain in between")
    - thalamus
    - hypothalamus (Greek for "under the thalamus")
    - pituitary gland
    - epithalamus
    - pineal gland
  - Telencephalon (Greek for "end brain", i.e. the most rostral part of the brain; also called forebrain)
    - TELENCEPHALON NUCLEI
      - putamen
      - caudate nucleus
      - putamen
      - globus pallidus
      - amygdala
    - CEREBRAL CORTEX
    - Archipallium (Greek for "first cloak", i.e. cortex that developed first; also called archeocortex)
      - hippocampus
    - Paleopallium (Greek for "ancient cloak"; also called "paleocortex")
      - priform(olfactory) cortex
      - parahippocampal gyrus
    - Neopallium (Greek for "new cloak"; also called "paleocortex"; also called neocortex and isocortex)
      - frontal lobe
      - temporal lobe
      - parietal lobe
      - occipital lobe
      - insula
      - cingulate cortex In addition, the brain is often subdivided into the following major parts:
- BRAINSTEM
  - Medulla
  - Pons
  - Midbrain
- CEREBELLUM
  - Cerebellar cortex
  - Cerebellar nuclei
- BASAL GANGLIA (some midbrain nuclei, such as substantia nigra are usually considered as basal ganglia)
  - Striatum (caudate nucleus and putamen)
  - Globus pallidus
- HIPPOCAMPUS
- AMYGDALA
- THALAMUS
- HYPOTHALAMUS
- CEREBRAL CORTEX Yet alternative classifications arrange brain areas into functional systems:
- Limbic system
- Sensory systems
  - Visual system
  - Olfactory system
  - Gustatory system
  - Auditory system
  - Somatosensory system
- Motor system
- Associative areas

Function

Associative areas Vertebrate brains receive signals through nerves arriving from the sensors of the organism, interpret those signals and formulate reactions based on built-in programs and learned experiences. A similarly extensive nerve network delivers signals from a brain to control muscles throughout a body. Anatomically, the majority of afferent and efferent nerves (with the exception of cranial nerves) are connected to the spinal cord, which then transfers the signals to the brain. Sensory input is processed by the brain to recognize danger, find food, identify potential mates and perform more sophisticated functions. Visual, touch, and auditory sensory pathways of vertebrates are routed to specific nuclei of the thalamus and then to regions of the cerebral cortex that are specific to each sensory system: the visual system, the auditory system and the somatosensory system. Olfactory pathways are routed to the olfactory bulb, then to various parts of the olfactory system. Taste is routed through the brainstem and then to other portions of the gustatory system. To control movement, the brain has several parallel systems of muscle control. The motor system controls voluntary muscle movement, aided by motor areas of the cerebral cortex, the cerebellum and the basal ganglia — the system that eventually projects to the spinal cord. Nuclei in the brainstem control many involuntary muscle functions such as heartrate and breathing. In addition, many automatic acts (simple reflexes, locomotion) can be controlled by the spinal cord alone. Brains also produce hormones that can influence organs and glands elsewhere in a body - conversely, brains also react to hormones produced elsewhere in the body. In mammals, most of these hormones are released into the circulatory system by a structure called the pituitary gland. It is hypothesized that developed brains derive consciousness from interaction among numerous systems within the brain. Cognitive processing in mammals occurs in the cerebral cortex but relies on mid-brain and limbic functions as well, especially those of the thalamus and hippocampus. Among "younger" (in an evolutionary sense) vertebrates, advanced processing involves progressively rostral (forward) regions of the brain. Hormones, incoming sensory information, and cognitive processing performed by the brain determine the brain state. Stimulus from any source can trigger a general arousal process that focuses cortical operations to processing of the new information. Cognitive priorities are constantly shifted by a variety of factors, such as hunger, fatigue, beliefs, unfamiliar information or threats. The simplest dichotomy related to processing of threats is the fight-or-flight response mediated by the amygdala, among other structures.

The study of the brain

Fields of study

Several areas of science specifically study the brain. Neuroscience seeks to understand the nervous system, including the brain, from a biological perspective. Psychology seeks to understand behavior and the brain. The terms neurology and psychiatry usually refer to medical applications of neuroscience and psychology, respectively. Cognitive science seeks to unify neuroscience and psychology with other fields that concern themselves with the brain, such as computer science (in Artificial intelligence and similar fields) and philosophy.

Methods of observation

Each method for observing activity in the brain has its advantages and drawbacks. Electrophysiology, in which wire electrodes are implanted in the brain, allows scientists to record the electrical activity of individual neurons or fields of neurons, but since it requires invasive surgery, this is a technique usually reserved for lab animals. By placing electrodes on the scalp, electroencephalography (EEG) measures brain waves, which are the mass changes in electrical current from the cerebral cortex, but can only detect changes over large areas of the brain and very little sub-cortical activity. Functional magnetic resonance imaging (fMRI) measures changes in blood flow in the brain, but the activity of neurons is not directly measured, nor can it be distinguished whether this activity is inhibitory or excitatory. Similarly, a PET (Positron Emission Tomography) Scan, is able to monitor glucose intake in different areas within the brain which is correlated the level of activity in that region. Behavioral tests can measure symptoms of disease and mental performance, but only provide indirect measurements of brain function and may not be practical in all animals. Finally, post-mortem analysis of the brain allows for the study of anatomy and protein expression patterns, but is only possible after the human or animal is dead.

History

Ancient Greeks had differing views on the function of the brain. Hippocrates believed the brain to be the seat of intelligence, but Aristotle held that the brain was a cooling mechanism for the blood, while the heart was the seat of intelligence. He reasoned that humans are more rational than the beasts because they have a proportionally larger brain to cool their hot-bloodedness (Bear, 2001). During the Roman Empire, the anatomist Galen dissected the brains of sheep. He concluded that since the cerebellum was hard on touch, it must control the muscles, while since the cerebrum was soft, it must be where the senses were processed. Galen further theorized that the brain functioned by movement of fluids through the ventricles (Bear, 2001). In the Age of Reason, René Descartes espoused a fluid mechanical view of the brain similar to Galen's theories. However, Descartes thought that although this explanation was adequate to explain the brain functions of animals, the higher mental functions of humans were accomplished by the soul. This theoretical separation of the mind and brain became known as the mind-body problem (Bear, 2001). In the mid-1600s, however, great progress in describing the anatomy of the brain was achieved with the works of English anatomist Thomas Willis and Flemish anatomist Vesalius. They dispelled many of the notions of Galen and Descartes and discovered many facts about the macro structure of the brain of animals and humans. In the 1700s, Luigi Galvani showed that electrically stimulating the sciatic nerve of a dissected frog caused movement of the attached muscle. His experiments led scientists away from the fluid mechanical theory of the brain and toward an electrical theory. In the 19th century, Galvani's work led to the development of research in bioelectricity and to the discovery of the membrane potential and action potential by researchers such as Emil du Bois-Reymond. The scientists of the 1800s debated whether areas of the brain corresponded to specific functions or if the brain functioned as a whole (the "aggregate field theory"). Jean Pierre Flourens championed the aggregate field theory in opposition to the pseudoscience of phrenology, founded by Franz Joseph Gall. However, the work of Paul Pierre Broca, Karl Wernicke, and Korbinian Brodmann eventually helped to show that areas of the brain had specific functions, though some functions were repeated, an idea known as parallel distributed processing (Kandel, 2001). As the 20th century approached, the anatomical works of Santiago Ramon y Cajal and Camillo Golgi laid the foundation for the study of individual neurons in the brain. Charles Scott Sherrington and Edgar Douglas Adrian furthered the study of neurons with the new techniques of electrodes and the electroencephalogram (EEG). Neurotransmitters were discovered and investigated by a number of scientists, including Otto Loewi, Henry Hallett Dale, Arvid Carlsson and many others. Modern Neuroscience experiences rapid development. The scientists use a variety of approaches to study the brain at different levels — from the molecules to systems. Extensive knowledge has been accumulated about the electrophysiological properties of different types of neurons and their responsiveness to neurotransmitters. Recordings from the brain of awake, behaving animals pioneered by Edward Evarts help to decode neuronal firing during different behaviors and cognitive processes. Miguel Nicolelis introduce multielectrode recording techniques which led to creation of brain-computer interfaces. Rapidly developing brain imaging allows scientists to study the brain in living humans and animals in ways that their predecessors could not.

The brain as a food

Like most other internal organs, the brain can serve as nourishment. For example, in the Southern United States canned pork brain in gravy can be purchased for consumption as food. This form of brain is often fried with scrambled egg to produce the famous "Eggs n' Brains". The brain of animals also features in the cuisine of France such as in the dish tête de veau, or head of calf. Although it might consist only of the outer meat of the skull and jaw, the full meal includes the brain, tongue and glands (the latter form being the favorite food of president Jacques Chirac). Similar delicacies from around the world include Mexican tacos de sesos (tacos made with cattle brain) and squirrel brain in the US South. The Anyang tribe of Cameroon practiced a tradition in which a new chief would consume the brain of a hunted gorilla while another senior member of the tribe would eat the heart. Consuming the brain and other nerve tissue of animals is not without its risks. The first problem is that the brain is made up of 60% fat due to the myelin (which by itself is 70% fat) insulating the axons of neurons and glia. As an example, a 5 oz. (0.14 kg) can of "Pork Brains in Milk Gravy", a single serving, contains 3500 milligrams of cholesterol, 1170% of our recommended daily intake. More importantly, humans can contract fatal transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease and other (prion diseases), as well as Bovine Spongiform Encephalopathy (colloquially known as "mad cow" disease) through the consumption of the infected nerve tissue of cattle and other animals - However, "there is no evidence that people can get mad cow disease from eating muscle meat". Another prion disease called kuru has been traced to a mourning ritual among the Fore people of Papua New Guinea in which those close to the dead would eat their brain to create a sense of immortality. Some archaeological evidence suggests that the mourning rituals of European neanderthals also involved the consumption of the brain. The practice of eating another human's brain has been depicted by Hollywood in Hannibal (film) and countless zombie movies. It is not only humans who eat the brains of other animals. The two species of chimpanzee, though generally vegetarian, are known to eat the brains of monkeys to obtain fat in their diet.

External links


- [http://www.stanford.edu/group/hopes/basics/braintut/ab0.html Brain Tutorial]
- [http://brainmuseum.org/ Comparative Mammalian Brain Collection]
- [http://www.rmcybernetics.com/science/cybernetics/ai_vision_perception_brain.htm RMCybernetics - The Brain and Artificial Intelligence]
- [http://braininfo.rprc.washington.edu BrainInfo for Neuroanatomy]
- [http://faculty.washington.edu/chudler/neurok.html Neuroscience for kids]
- [http://3dscience.com/advancedsearch.asp?stS=brain&cboMatch=Any&selectcategory=0&txtMinPrice=&txtMaxPrice= Free Brain Medical Clip Art].
- [http://purl.net/net/neurowiki neuroscience wiki]
- [http://www.brainmaps.org/ BrainMaps.org], interactive high-resolution digital brain atlas based on scanned images of serial sections of both primate and non-primate brains

Related topics


- A/S ratio
- Avian pallium
- Brain damage
- Brain-computer interface
- Coma
- Human brain
- Persistent vegetative state
- Regions in the human brain
- The Memory-Prediction Framework
- Metastability in the brain
- Neuroendocrinology
- Traumatic brain injury

References


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Notes

The following are the sources for individual facts, statistics and information included in the article:
- Statistic from page 161 of Basic Histology: Text and Atlas, 10th ed. by L.C. Junqueira, and J. Carneiro.
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- Category:Central nervous system Category:Cerebrum ja:脳 ko:뇌 simple:Brain th:สมอง

Anorexia

Anorexia (deriving from the Greek όρεξη (orexe) = appetite) is the decreased sensation of appetite. While the term in non-scientific publications is often used interchangably with one of its subtypes, anorexia nervosa, there are many possible causes for a decreased appetite, some of which may be harmless while others pose significant risk for the person.

Causes

Common disorders that cause anorexia include anorexia nervosa, severe depression, cancer, dementia, AIDS, and chronic renal disease. Environmentally induced disorders, such as altitude sickness, can also trigger an acute form of anorexia. Anorexia may also be seen in congestive heart failure, perhaps due to congestion of the liver with venous blood. Although the presenting symptom (the one which prompts a patient to seek medical attention) in acute appendicitis is abdominal pain, the presence of anorexia is requisite to making the diagnosis. Some medications, antidepressants for example, can have anorexia as a side effect. Most notoriously, however, chemicals that are a member of the phenethylamine family are known to have more intense anorectic properties. For this reason, many individuals suffering from anorexia nervosa seek to use these medications as a crutch. Such prescription medications include Ritalin, Adderall, Dexedrine, and Desoxyn. In some cases, these medications are prescribed to patients prior to undergoing an operation requiring general anesthesia. This is a prophylactic measure taken to ensure no food will back up into the esophagus and cause the patient to stop breathing during the procedure.

Results

Inability to eat in the long term may lead to involuntary weight loss, may contribute to cachexia (wasting) and to malnutrition. Category:Symptoms

Anorexia nervosa

Anorexia nervosa is an eating disorder characterized by voluntary starvation and exercise stress. Anorexia nervosa is a complex disease, involving psychological, sociological and physiological components. A person who is suffering from anorexia is referred to as 'anorexic' or (less commonly) 'anorectic'. "Anorectic" is the noun form, where "anorexic" is the adjectival form. These two are often used incorrectly when applied. Although technically incorrect, the term is frequently shortened to anorexia, which simply refers to the medical symptom of lost appetite. In this article, anorexia will be used synonymously with anorexia nervosa. Anorectic can also refer to appetite-suppressing drugs.

Characteristics

The causes of anorexia are a matter of debate in medical circles and society in general. General perspectives fit between the poles of it being physiological or psychological (with the potential for sociological and cultural influences being a cause to various degrees) in origin. Some now take the opinion that it is a mix of both, in that it is a psychological condition which is often (though not inherently) borne of certain conducive neurophysiologic conditions.

Physiological

The primary physiological characteristics of anorexia nervosa are:
- voluntary starvation
- exercise stress
- obsessive-compulsive behavior
- autism spectrum disorder In addition to intentional starvation, subjects will also take part in a high level of physical activity. Anorexia nervosa also has a negative impact on the immune system and the central nervous system (CNS). It is also thought to be linked to serotonin and dopamine abnormalities. Many individuals develop obsessive-compulsive symptoms as part of their disease. Some have an eating-disordered parent, presumably connected with shared genetic characteristics. Additionaly, some 1/3 of anorexic people meet diagnostic criteria for an autism spectrum disorder, a sub-group that is especially difficult to treat successfully [http://www.jaacap.com/pt/re/jaacap/abstract.00004583-199911000-00013.htm;jsessionid=DQzMCL1lGB5RkMKPhw1UwDkfxHDPpAQ2kX68hvsgQ2s98fH7mf0l!-2030079693!-949856145!9001!-1]. Thus, anorexia may be the result of undetected autism in women [http://news.scotsman.com/topics.cfm?tid=702&id=713402005]. Anorexic subjects will often go through a cycle of recovery and relapse, unless weight is restored long-term.

Neurochemistry abnormalities

There is increasing speculation that the onset of anorexia has a genetic component, with a certain gene linked to abnormalities with the neurotransmitter chemical serotonin being shown to be more common amongst sufferers than the general population. Such genetic characteristics might potentially equate to an easier path towards overly high serotonin levels, thus instilling heightened levels of anxiety and the like. Biologically, when a person is in a state of starvation, their levels of serotonin decrease, and thence increase again upon the consumption of food because of the tryptophan amino acids contained therein (tryptophan is used by the body to synthesise serotonin). This raises the spectre that the anorexic is conditioned into avoiding food to reduce his or her anxiety, and that there may be yet another layer of complexity with respects to the cause/effect relationship between physiological factors and the mental beliefs of the anorexic.

Blood chemistry abnormalities: dietary minerals and heavy metals

Victims of mercury, lead, beryllium and