A drug is any substance that, when inhaled, smoked, absorbed via a patch on the skin, or dissolved under the tongue causes a physiological change in the body. In pharmacology, a drug is a chemical substance of known structure, other than a nutrient of an essential dietary ingredient, when administered to a living organism, produces a biological effect. A pharmaceutical drug called a medication or medicine, is a chemical substance used to treat, prevent, or diagnose a disease or to promote well-being. Traditionally drugs were obtained through extraction from medicinal plants, but more also by organic synthesis. Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders. Pharmaceutical drugs are classified into drug classes—groups of related drugs that have similar chemical structures, the same mechanism of action, a related mode of action, that are used to treat the same disease; the Anatomical Therapeutic Chemical Classification System, the most used drug classification system, assigns drugs a unique ATC code, an alphanumeric code that assigns it to specific drug classes within the ATC system.
Another major classification system is the Biopharmaceutics Classification System. This classifies drugs according to their permeability or absorption properties. Psychoactive drugs are chemical substances that affect the function of the central nervous system, altering perception, mood or consciousness, they include alcohol, a depressant, the stimulants nicotine and caffeine. These three are the most consumed psychoactive drugs worldwide and are considered recreational drugs since they are used for pleasure rather than medicinal purposes. Other recreational drugs include hallucinogens and amphetamines and some of these are used in spiritual or religious settings; some drugs can cause addiction and all drugs can have side effects. Excessive use of stimulants can promote stimulant psychosis. Many recreational drugs are illicit and international treaties such as the Single Convention on Narcotic Drugs exist for the purpose of their prohibition. In English, the noun "drug" is thought to originate from Old French "drogue" deriving into "droge-vate" from Middle Dutch meaning "dry barrels", referring to medicinal plants preserved in them.
The transitive verb "to drug" arose and invokes the psychoactive rather than medicinal properties of a substance. A medication or medicine is a drug taken to cure or ameliorate any symptoms of an illness or medical condition; the use may be as preventive medicine that has future benefits but does not treat any existing or pre-existing diseases or symptoms. Dispensing of medication is regulated by governments into three categories—over-the-counter medications, which are available in pharmacies and supermarkets without special restrictions. In the United Kingdom, behind-the-counter medicines are called pharmacy medicines which can only be sold in registered pharmacies, by or under the supervision of a pharmacist; these medications are designated by the letter P on the label. The range of medicines available without a prescription varies from country to country. Medications are produced by pharmaceutical companies and are patented to give the developer exclusive rights to produce them; those that are not patented are called generic drugs since they can be produced by other companies without restrictions or licenses from the patent holder.
Pharmaceutical drugs are categorised into drug classes. A group of drugs will share a similar chemical structure, or have the same mechanism of action, the same related mode of action or target the same illness or related illnesses; the Anatomical Therapeutic Chemical Classification System, the most used drug classification system, assigns drugs a unique ATC code, an alphanumeric code that assigns it to specific drug classes within the ATC system. Another major classification system is the Biopharmaceutics Classification System; this groups drugs according to their permeability or absorption properties. Some religions ethnic religions are based on the use of certain drugs, known as entheogens, which are hallucinogens,—psychedelics, dissociatives, or deliriants; some drugs used as entheogens include kava which can act as a stimulant, a sedative, a euphoriant and an anesthetic. The roots of the kava plant are used to produce a drink, consumed throughout the cultures of the Pacific Ocean; some shamans from different cultures use entheogens, defined as "generating the divine within" to achieve religious ecstasy.
Amazonian shamans use ayahuasca a hallucinogenic brew for this purpose. Mazatec shamans have a long and continuous tradition of religious use of Salvia divinorum a psychoactive plant, its use is to facilitate visionary states of consciousness during spiritual healing sessions. Silene undulata is used as an entheogen, its root is traditionally used to induce vivid lucid dreams during the initiation process of shamans, classifying it a occurring oneirogen similar to the more well-known dream herb Calea ternifolia. Peyote a small spineless cactus has been a
In physiology, an action potential occurs when the membrane potential of a specific axon location rises and falls: this depolarisation causes adjacent locations to depolarise. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, endocrine cells, in some plant cells. In neurons, action potentials play a central role in cell-to-cell communication by providing for—or with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas, they provoke release of insulin. Action potentials in neurons are known as "nerve impulses" or "spikes", the temporal sequence of action potentials generated by a neuron is called its "spike train".
A neuron that emits an action potential, or nerve impulse, is said to "fire". Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane; these channels are shut when the membrane potential is near the resting potential of the cell, but they begin to open if the membrane potential increases to a defined threshold voltage, depolarising the transmembrane potential. When the channels open, they allow an inward flow of sodium ions, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential; this causes more channels to open, producing a greater electric current across the cell membrane and so on. The process proceeds explosively until all of the available ion channels are open, resulting in a large upswing in the membrane potential; the rapid influx of sodium ions causes the polarity of the plasma membrane to reverse, the ion channels rapidly inactivate. As the sodium channels close, sodium ions can no longer enter the neuron, they are actively transported back out of the plasma membrane.
Potassium channels are activated, there is an outward current of potassium ions, returning the electrochemical gradient to the resting state. After an action potential has occurred, there is a transient negative shift, called the afterhyperpolarization. In animal cells, there are two primary types of action potentials. One type is generated by the other by voltage-gated calcium channels. Sodium-based action potentials last for under one millisecond, but calcium-based action potentials may last for 100 milliseconds or longer. In some types of neurons, slow calcium spikes provide the driving force for a long burst of emitted sodium spikes. In cardiac muscle cells, on the other hand, an initial fast sodium spike provides a "primer" to provoke the rapid onset of a calcium spike, which produces muscle contraction. In the Hodgkin–Huxley membrane capacitance model, the speed of transmission of an action potential was undefined and it was assumed that adjacent areas became depolarised due to released ion interference with neighbouring channels.
Measurements of ion diffusion and radii have since shown this not to be possible. Moreover, contradictory measurements of entropy changes and timing disputed the capacitance model as acting alone. Nearly all cell membranes in animals and fungi maintain a voltage difference between the exterior and interior of the cell, called the membrane potential. A typical voltage across an animal cell membrane is −70 mV; this means that the interior of the cell has a negative voltage of one-fifteenth of a volt relative to the exterior. In most types of cells, the membrane potential stays constant; some types of cells, are electrically active in the sense that their voltages fluctuate over time. In some types of electrically active cells, including neurons and muscle cells, the voltage fluctuations take the form of a rapid upward spike followed by a rapid fall; these up-and-down cycles are known as action potentials. In some types of neurons, the entire up-and-down cycle takes place in a few thousandths of a second.
In muscle cells, a typical action potential lasts about a fifth of a second. In some other types of cells, in plants, an action potential may last three seconds or more; the electrical properties of a cell are determined by the structure of the membrane that surrounds it. A cell membrane consists of a lipid bilayer of molecules in which larger protein molecules are embedded; the lipid bilayer is resistant to movement of electrically charged ions, so it functions as an insulator. The large membrane-embedded proteins, in contrast, provide channels through which ions can pass across the membrane. Action potentials are driven by channel proteins whose configuration switches between closed and open states as a function of the voltage difference between the interior and exterior of the cell; these voltage-sensitive proteins are known as voltage-gated ion channels. All cells in animal body tissues are electrically polarized – in other words, they maintain a voltage difference across the cell's plasma membrane, known as the membrane potential.
This electrical polarization results from a complex interplay between protein structures embedded in the membrane called ion pumps and ion channels. In neurons, the types of ion channels in the membrane vary across different parts of the cell, giving the dendrites and cell body different electrical properties; as a result, some parts of the membrane of a neuron may be excitable (capable of generating action potentia
Cocaine known as coke, is a strong stimulant used as a recreational drug. It is snorted, inhaled as smoke, or dissolved and injected into a vein. Mental effects may include loss of contact with reality, an intense feeling of happiness, or agitation. Physical symptoms may include a fast heart rate and large pupils. High doses can result in high blood pressure or body temperature. Effects begin within seconds to last between five and ninety minutes. Cocaine has a small number of accepted medical uses such as numbing and decreasing bleeding during nasal surgery. Cocaine is addictive due to its effect on the reward pathway in the brain. After a short period of use, there is a high risk, its use increases the risk of stroke, myocardial infarction, lung problems in those who smoke it, blood infections, sudden cardiac death. Cocaine sold on the street is mixed with local anesthetics, quinine, or sugar, which can result in additional toxicity. Following repeated doses a person may have decreased ability to feel pleasure and be physically tired.
Cocaine acts by inhibiting the reuptake of serotonin and dopamine. This results in greater concentrations of these three neurotransmitters in the brain, it can cross the blood–brain barrier and may lead to the breakdown of the barrier. Cocaine is a occurring substance found in the coca plant, grown in South America. In 2013, 419 kilograms were produced legally, it is estimated. With further processing crack cocaine can be produced from cocaine. Cocaine is the second most used illegal drug globally, after cannabis. Between 14 and 21 million people use the drug each year. Use is highest in North America followed by South America. Between one and three percent of people in the developed world have used cocaine at some point in their life. In 2013, cocaine use directly resulted in 4,300 deaths, up from 2,400 in 1990; the leaves of the coca plant have been used by Peruvians since ancient times. Cocaine was first isolated from the leaves in 1860. Since 1961, the international Single Convention on Narcotic Drugs has required countries to make recreational use of cocaine a crime.
Topical cocaine can be used as a local numbing agent to help with painful procedures in the mouth or nose. Cocaine is now predominantly used for lacrimal duct surgery; the major disadvantages of this use are cocaine's potential for cardiovascular toxicity and pupil dilation. Medicinal use of cocaine has decreased as other synthetic local anesthetics such as benzocaine, proparacaine and tetracaine are now used more often. If vasoconstriction is desired for a procedure, the anesthetic is combined with a vasoconstrictor such as phenylephrine or epinephrine; some ENT specialists use cocaine within the practice when performing procedures such as nasal cauterization. In this scenario dissolved cocaine is soaked into a ball of cotton wool, placed in the nostril for the 10–15 minutes before the procedure, thus performing the dual role of both numbing the area to be cauterized, vasoconstriction; when used this way, some of the used cocaine may be absorbed through oral or nasal mucosa and give systemic effects.
An alternative method of administration for ENT surgery is mixed with adrenaline and sodium bicarbonate, as Moffett's solution. Cocaine is a powerful nervous system stimulant, its effects can last from 30 minutes to an hour. The duration of cocaine's effects depends on the route of administration. Cocaine can be in the form of fine white powder, bitter to the taste; when inhaled or injected, it causes a numbing effect. Crack cocaine is a smokeable form of cocaine made into small "rocks" by processing cocaine with sodium bicarbonate and water. Crack cocaine is referred to. Cocaine use leads to increases in alertness, feelings of well-being and euphoria, increased energy and motor activity, increased feelings of competence and sexuality. Coca leaves are mixed with an alkaline substance and chewed into a wad, retained in the mouth between gum and cheek and sucked of its juices; the juices are absorbed by the mucous membrane of the inner cheek and by the gastrointestinal tract when swallowed. Alternatively, coca leaves can be consumed like tea.
Ingesting coca leaves is an inefficient means of administering cocaine. Because cocaine is hydrolyzed and rendered inactive in the acidic stomach, it is not absorbed when ingested alone. Only when mixed with a alkaline substance can it be absorbed into the bloodstream through the stomach; the efficiency of absorption of orally administered cocaine is limited by two additional factors. First, the drug is catabolized by the liver. Second, capillaries in the mouth and esophagus constrict after contact with the drug, reducing the surface area over which the drug can be absorbed. Cocaine metabolites can be detected in the urine of subjects that have sipped one cup of coca leaf infusion. Orally administered cocaine takes 30 minutes to enter the bloodstream. Only a third of an oral dose is absorbed, although absorption has been shown to reach 60% in controlled settings. Given the slow rate of absorption, maximum physiological and psychotropic effects are attained 60 minutes after cocaine is administered by ingestion.
While the onset of these effects is slow, the effects are sustained for approxima
Benzocaine, sold under the brand name Orajel among others, is an ester local anesthetic used as a topical pain reliever or in cough drops. It is the active ingredient in many over-the-counter anesthetic ointments such as products for oral ulcers, it is combined with antipyrine to form A/B otic drops to relieve ear pain and remove earwax. It is not recommended in children younger than two years old, it was first described in 1895 and approved for medical use in 1902. Benzocaine is indicated to treat a variety of pain-related conditions, it may be used for: Local anesthesia of oral and pharyngeal mucous membranes Otic pain Surgical or procedural local anesthesia Benzocaine is used as a key ingredient in numerous pharmaceuticals: Some glycerol-based ear medications for use in removing excess wax as well as relieving ear conditions such as otitis media and swimmers ear. Some previous diet products such as Ayds; some condoms designed to prevent premature ejaculation. Benzocaine inhibits sensitivity on the penis, can allow for an erection to be maintained longer by delaying ejaculation.
Conversely, an erection will fade faster if stimulus is interrupted. Benzocaine mucoadhesive patches have been used in reducing orthodontic pain. In Poland it is included, together with menthol and zinc oxide, in the liquid powder used after mosquito bites. Today's ready. Benzocaine can come in a variety of preparations including: Oral preparations: Lozenges Throat Spray Topical preparations: Aerosol Gel Paste Otic preparations: Solution Benzocaine is well-tolerated and non-toxic when applied topically as recommended. However, there have been reports of serious, life-threatening adverse effects with over-application of topical products or when applying topical products that contain high concentrations of benzocaine to the skin. Overapplication of oral anesthetics such as benzocaine can increase the risk of pulmonary aspiration by relaxing the gag-reflex and allowing regurgitated stomach contents or oral secretions to enter the airway. Applying an oral anesthetic and consuming beverages before going to bed can be hazardous.
The topical use of higher concentration benzocaine spray products applied to the mouth or mucous membranes has been found to be a cause of methemoglobinemia, a disorder in which the amount of oxygen carried by the blood is reduced. This side effect is most common in children under 2 years of age; as a result, the FDA has stated that benzocaine products should not be used in children under 2 years of age, unless directed by and supervised by a healthcare professional. Symptoms of methemoglobinemia occur within minutes to hours of applying benzocaine, can occur upon the first-time use or after additional use. Benzocaine may cause allergic reactions; these include: Contact dermatitis Anaphylaxis Pain is caused by the stimulation of free nerve endings. When the nerve endings are stimulated, sodium enters the neuron, causing depolarization of the nerve and subsequent initiation of an action potential; the action potential is propagated down the nerve toward the central nervous system, which interprets this as pain.
Benzocaine acts to inhibit the voltage-dependent sodium channels on the neuron membrane, stopping the propagation of the action potential. Benzocaine is the ethyl ester of p-aminobenzoic acid, it can be prepared from PABA and ethanol by Fischer esterification or via the reduction of ethyl p-nitrobenzoate. Benzocaine is sparingly soluble in water; the melting point of benzocaine is 88–90 °C, the boiling point is about 310 °C. The density of benzocaine is 1.17 g/cm3. Benzocaine is found in Britain, as an impurity in street cocaine and as a bulking agent in "legal highs". Whilst giving a numbing effect similar to cocaine on users' mucous membranes, it does not produce the effects of cocaine. Benzocaine was used in synthesis of leteprinim. Treatment of benzocaine with hydrazine leads to aminostimil - a compound related to isoniazid. Benzocaine can be prepared by esterification using 4-aminobenzoic ethanol, it can be prepared by reduction of ethyl 4-nitrobenzoate to the amine. In industrial practice, the reducing agent is iron and water in the presence of a little acid.
Benzocaine was first synthesized in 1890 by the German chemist Eduard Ritsert, in the town of Eberbach and introduced to the market in 1902 under the name "Anästhesin". A bath solution of benzocaine has been used to anesthetize amphibians for surgery. Public Health Advisory: Benzocaine Sprays by the Food and Drug Administration
An axon, or nerve fiber, is a long, slender projection of a nerve cell, or neuron, in vertebrates, that conducts electrical impulses known as action potentials away from the nerve cell body. The function of the axon is to transmit information to different neurons and glands. In certain sensory neurons, such as those for touch and warmth, the axons are called afferent nerve fibers and the electrical impulse travels along these from the periphery to the cell body, from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction has caused many inherited and acquired neurological disorders which can affect both the peripheral and central neurons. Nerve fibers are classed into three types – group A nerve fibers, group B nerve fibers, group C nerve fibers. Groups A and B are myelinated, group C are unmyelinated; these groups include both sensory fibers and motor fibers. Another classification groups only the sensory fibers as Type I, Type II, Type III, Type IV. An axon is one of two types of cytoplasmic protrusions from the cell body of a neuron.
Axons are distinguished from dendrites by several features, including shape and function. Some types of neurons have no transmit signals from their dendrites. In some species, axons can emanate from dendrites and these are known as axon-carrying dendrites. No neuron has more than one axon. Axons are covered by a membrane known as an axolemma. Most axons branch, in some cases profusely; the end branches of an axon are called telodendria. The swollen end of a telodendron is known as the axon terminal which joins the dendron or cell body of another neuron forming a synaptic connection. Axons make contact with other cells—usually other neurons but sometimes muscle or gland cells—at junctions called synapses. In some circumstances, the axon of one neuron may form a synapse with the dendrites of the same neuron, resulting in an autapse. At a synapse, the membrane of the axon adjoins the membrane of the target cell, special molecular structures serve to transmit electrical or electrochemical signals across the gap.
Some synaptic junctions appear along the length of an axon as it extends—these are called en passant synapses and can be in the hundreds or the thousands along one axon. Other synapses appear as terminals at the ends of axonal branches. A single axon, with all its branches taken together, can innervate multiple parts of the brain and generate thousands of synaptic terminals. A bundle of axons make a nerve tract in the central nervous system, a fascicle in the peripheral nervous system. In placental mammals the largest white matter tract in the brain is the corpus callosum, formed of some 20 million axons in the human brain. Axons are the primary transmission lines of the nervous system, as bundles they form nerves; some axons can extend up to more while others extend as little as one millimeter. The longest axons in the human body are those of the sciatic nerve, which run from the base of the spinal cord to the big toe of each foot; the diameter of axons is variable. Most individual axons are microscopic in diameter.
The largest mammalian axons can reach a diameter of up to 20 µm. The squid giant axon, specialized to conduct signals rapidly, is close to 1 millimetre in diameter, the size of a small pencil lead; the numbers of axonal telodendria can differ from one nerve fiber to the next. Axons in the central nervous system show multiple telodendria, with many synaptic end points. In comparison, the cerebellar granule cell axon is characterized by a single T-shaped branch node from which two parallel fibers extend. Elaborate branching allows for the simultaneous transmission of messages to a large number of target neurons within a single region of the brain. There are two types of axons in the nervous system: unmyelinated axons. Myelin is a layer of a fatty insulating substance, formed by two types of glial cells Schwann cells and oligodendrocytes. In the peripheral nervous system Schwann cells form the myelin sheath of a myelinated axon. In the central nervous system oligodendrocytes form the insulating myelin.
Along myelinated nerve fibers, gaps in the myelin sheath known as nodes of Ranvier occur at evenly spaced intervals. The myelination enables an rapid mode of electrical impulse propagation called saltatory conduction; the myelinated axons from the cortical neurons form the bulk of the neural tissue called white matter in the brain. The myelin gives the white appearance to the tissue in contrast to the grey matter of the cerebral cortex which contains the neuronal cell bodies. A similar arrangement is seen in the cerebellum. Bundles of myelinated axons make up the nerve tracts in the CNS. Where these tracts cross the midline of the brain to connect opposite regions they are called commissures; the largest of these is the corpus callosum that connects the two cerebral hemispheres, this has around 20 million axons. The structure of a neuron is seen to consist of two separate functional regions, or compartments – the cell body together with the dendrites as one region, the axonal region as the other.
The axonal region or compart
Anesthesiology, anaesthesia or anaesthetics is the medical speciality concerned with the total perioperative care of patients before and after surgery. It encompasses anesthesia, intensive care medicine, critical emergency medicine, pain medicine. A physician specialised in this field of medicine is called an anesthesiologist, anaesthesiologist or anaesthetist, depending on the country; the core element of the specialty is the study and use of anesthesia and anesthetics, since the 19th century anesthesiology has developed from an experimental field with non-specialist practitioners using novel, untested drugs and techniques into what is now a refined and effective field of medicine. In some countries, anesthesiologists comprise the largest single cohort of doctors in hospitals, their role can now extend far beyond the traditional role of anesthesia care in the operating room, into fields such as providing pre-hospital emergency medicine, running intensive care units, transporting critically ill patients between facilities, prehabilitation programs to optimize patients for surgery.
Various names are used for the specialty, those doctors who practise it, in different parts of the world: In North America and China, the medical study and application of anesthetics is called anesthesiology, a physician in the specialty is called an anesthesiologist. In these countries, the word "anesthetist" is used to refer to advanced non-physician providers of anesthesia services such as anesthesiologist assistants and nurse anesthetists. In some countries that are current or former members of the Commonwealth of Nations–namely, United Kingdom, New Zealand and South Africa–the medical specialty is instead referred to as anaesthesia or anaesthetics, with an extra "a"; as such, in these countries the same term may be used to refer to the overall medical specialty, the medications and techniques that are used, the resulting state of loss of sensation. The term anaesthetist is used only to refer to a physician practising in the field; some countries which used "anaesthesia" and "anaesthetist", such as Ireland and Hong Kong, have transitioned to "anaesthesiology" and "anaesthesiologist", or are in the process of transition.
In most other parts of the world, the spelling anaesthesiology is most used when writing in English, a physician practising it is termed an anaesthesiologist. This is the spelling adopted by the World Federation of Societies of Anaesthesiologists and most of its most of its member societies, as well as the European Society of Anaesthesiology, it is the most used term found in the titles of medical journals; as a specialty, the core element of anesthesiology is the practice of anesthesia. This comprises the use of various injected and inhaled medications to produce a loss of sensation in patients, making it possible to carry out procedures that would otherwise cause intolerable pain or be technically unfeasible. Safe anesthesia requires in-depth knowledge of various invasive and non-invasive organ support techniques that are used to control patients' vital functions while under the effects of anaesthetic drugs. Anesthesiologists are expected to have expert knowledge of human physiology, medical physics, pharmacology, as well as a broad general knowledge of all areas of medicine and surgery in all ages of patients, with a particular focus on those aspects which may impact on a surgical procedure.
In recent decades, the role of anesthesiologists has broadened to focus not just on administering anesthetics during the surgical procedure itself, but beforehand in order to identify high-risk patients and optimize their fitness, during the procedure to maintain situational awareness of the surgery itself so as to improve safety, as well as afterwards in order to promote and enhance recovery. This has been termed "perioperative medicine"; the concept of intensive care medicine arose in the 1950s and 1960s, with anesthesiologists taking organ support techniques that had traditionally been used only for short periods during surgical procedures, applying these therapies to patients with organ failure, who might require vital function support for extended periods until the effects of the illness could be reversed. The first intensive care unit was opened by Bjørn Aage Ibsen in Copenhagen in 1953, prompted by a polio epidemic during which many patients required prolonged artificial ventilation.
In many countries, intensive care medicine is considered to be a subspecialty of anesthesiology, anesthesiologists rotate between duties in the operating room and the intensive care unit. This allows continuity of care when patients are admitted to the ICU after their surgery, it means that anesthesiologists can maintain their expertise at invasive procedures and vital function support in the controlled setting of the operating room, while applying those skills in the more dangerous setting of the critically ill patient. In other countries, intensive care medicine has evolved further to become a separate medical specialty in its own right, or has become a "supra-specialty" which may be practiced by doctors from various base specialties such as anesthesiology, emergency medicine, general medicine, surgery or neurology. Anesthesiologists have key roles in major trauma, airway management, caring other patients outside the operating theatre who have critical emergencies that pose an immediate threat to life, a
Consciousness is the state or quality of awareness or of being aware of an external object or something within oneself. It has been defined variously in terms of sentience, qualia, the ability to experience or to feel, having a sense of selfhood or soul, the fact that there is something "that it is like" to "have" or "be" it, the executive control system of the mind. Despite the difficulty in definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is; as Max Velmans and Susan Schneider wrote in The Blackwell Companion to Consciousness: "Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives."Western philosophers, since the time of Descartes and Locke, have struggled to comprehend the nature of consciousness and identify its essential properties. Issues of concern in the philosophy of consciousness include whether the concept is fundamentally coherent.
Thanks to developments in technology over the past few decades, consciousness has become a significant topic of interdisciplinary research in cognitive science, with significant contributions from fields such as psychology, anthropology and neuroscience. The primary focus is on understanding what it means biologically and psychologically for information to be present in consciousness—that is, on determining the neural and psychological correlates of consciousness; the majority of experimental studies assess consciousness in humans by asking subjects for a verbal report of their experiences. Issues of interest include phenomena such as subliminal perception, denial of impairment, altered states of consciousness produced by alcohol and other drugs, or spiritual or meditative techniques. In medicine, consciousness is assessed by observing a patient's arousal and responsiveness, can be seen as a continuum of states ranging from full alertness and comprehension, through disorientation, loss of meaningful communication, loss of movement in response to painful stimuli.
Issues of practical concern include how the presence of consciousness can be assessed in ill, comatose, or anesthetized people, how to treat conditions in which consciousness is impaired or disrupted. The degree of consciousness is measured by standardized behavior observation scales such as the Glasgow Coma Scale; the origin of the modern concept of consciousness is attributed to John Locke's Essay Concerning Human Understanding, published in 1690. Locke defined consciousness as "the perception of what passes in a man's own mind", his essay influenced the 18th-century view of consciousness, his definition appeared in Samuel Johnson's celebrated Dictionary. "Consciousness" is defined in the 1753 volume of Diderot and d'Alembert's Encyclopédie, as "the opinion or internal feeling that we ourselves have from what we do." The earliest English language uses of "conscious" and "consciousness" date back, however, to the 1500s. The English word "conscious" derived from the Latin conscius, but the Latin word did not have the same meaning as our word—it meant "knowing with", in other words "having joint or common knowledge with another".
There were, many occurrences in Latin writings of the phrase conscius sibi, which translates as "knowing with oneself", or in other words "sharing knowledge with oneself about something". This phrase had the figurative meaning of "knowing that one knows", as the modern English word "conscious" does. In its earliest uses in the 1500s, the English word "conscious" retained the meaning of the Latin conscius. For example, Thomas Hobbes in Leviathan wrote: "Where two, or more men, know of one and the same fact, they are said to be Conscious of it one to another." The Latin phrase conscius sibi, whose meaning was more related to the current concept of consciousness, was rendered in English as "conscious to oneself" or "conscious unto oneself". For example, Archbishop Ussher wrote in 1613 of "being so conscious unto myself of my great weakness". Locke's definition from 1690 illustrates. A related word was conscientia, which means moral conscience. In the literal sense, "conscientia" means knowledge-with, that is, shared knowledge.
The word first appears in Latin juridical texts by writers such as Cicero. Here, conscientia is the knowledge. René Descartes is taken to be the first philosopher to use conscientia in a way that does not fit this traditional meaning. Descartes used conscientia the way modern speakers would use "conscience". In Search after Truth he says "conscience or internal testimony"; the dictionary meanings of the word consciousness extend through several centuries and several associated related meanings. These have ranged from formal definitions to definitions attempting to capture the less captured and more debated meanings and usage of the wor