165-407: Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with the surrounding environment. While sleep differs from wakefulness in terms of the ability to react to stimuli , it still involves active brain patterns, making it more reactive than
330-405: A coma or disorders of consciousness . Sleep occurs in repeating periods , during which the body alternates between two distinct modes: REM and non-REM sleep . Although REM stands for "rapid eye movement", this mode of sleep has many other aspects, including virtual paralysis of the body. Dreams are a succession of images, ideas, emotions, and sensations that usually occur involuntarily in
495-404: A 24-hour cycle, whereas in monophasic sleep this occurs all at once. Under experimental conditions, humans tend to alternate more frequently between sleep and wakefulness (i.e., exhibit more polyphasic sleep) if they have nothing better to do. Given a 14-hour period of darkness in experimental conditions, humans tended towards bimodal sleep, with two sleep periods concentrated at the beginning and at
660-407: A brain area directly above the optic chiasm , is presently considered the most important nexus for this process; however, secondary clock systems have been found throughout the body. An organism whose circadian clock exhibits a regular rhythm corresponding to outside signals is said to be entrained ; an entrained rhythm persists even if the outside signals suddenly disappear. If an entrained human
825-417: A complex interface region known as the musculotendinous junction also known as the myotendinous junction , an area specialised for the primary transmission of force. At the muscle-tendon interface, force is transmitted from the sarcomeres in the muscle cells to the tendon. Muscles and tendons develop in close association, and after their joining at the myotendinous junction they constitute a dynamic unit for
990-454: A concept of consciousness. He does not use any single word or terminology that is clearly similar to the phenomenon or concept defined by John Locke . Victor Caston contends that Aristotle did have a concept more clearly similar to perception . Modern dictionary definitions of the word consciousness evolved over several centuries and reflect a range of seemingly related meanings, with some differences that have been controversial, such as
1155-400: A distinct type of substance not governed by the laws of physics), and property dualism (which holds that the laws of physics are universally valid but cannot be used to explain the mind). The three main types of monism are physicalism (which holds that the mind consists of matter organized in a particular way), idealism (which holds that only thought or experience truly exists, and matter
1320-410: A factor which may exacerbate disruption of the circadian cycle. Scientific studies on sleep have shown that sleep stage at awakening is an important factor in amplifying sleep inertia . Determinants of alertness after waking up include quantity/quality of the sleep, physical activity the day prior, a carbohydrate-rich breakfast, and a low blood glucose response to it. Sleep timing is controlled by
1485-605: A full eight hours. Researchers have found that sleeping 6–7 hours each night correlates with longevity and cardiac health in humans, though many underlying factors may be involved in the causality behind this relationship. Sleep difficulties are furthermore associated with psychiatric disorders such as depression , alcoholism , and bipolar disorder . Up to 90 percent of adults with depression are found to have sleep difficulties. Dysregulation detected by EEG includes disturbances in sleep continuity, decreased delta sleep and altered REM patterns with regard to latency, distribution across
1650-403: A function of the amount of time elapsed since the last adequate sleep episode) must be balanced against the circadian element for satisfactory sleep. Along with corresponding messages from the circadian clock, this tells the body it needs to sleep. The timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening: maximum concentration of
1815-409: A good night's sleep. The American Academy of Sleep Medicine (AASM) divides NREM into three stages: N1, N2, and N3, the last of which is also called delta sleep or slow-wave sleep . The whole period normally proceeds in the order: N1 → N2 → N3 → N2 → REM. REM sleep occurs as a person returns to stage 2 or 1 from a deep sleep. There is a greater amount of deep sleep (stage N3) earlier in the night, while
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#17328511431831980-436: A grasp of what consciousness means. Many fall into the trap of equating consciousness with self-consciousness —to be conscious it is only necessary to be aware of the external world. Consciousness is a fascinating but elusive phenomenon: it is impossible to specify what it is, what it does, or why it has evolved. Nothing worth reading has been written on it. Using 'awareness', however, as a definition or synonym of consciousness
2145-558: A higher capability for electrochemical transmission of action potentials and a rapid level of calcium release and uptake by the sarcoplasmic reticulum. The fast twitch fibers rely on a well-developed, anaerobic , short term, glycolytic system for energy transfer and can contract and develop tension at 2–3 times the rate of slow twitch fibers. Fast twitch muscles are much better at generating short bursts of strength or speed than slow muscles, and so fatigue more quickly. The slow twitch fibers generate energy for ATP re-synthesis by means of
2310-757: A higher density of capillaries . However, muscle cells cannot divide to produce new cells, and as a result there are fewer muscle cells in an adult than in a newborn. There are a number of terms used in the naming of muscles including those relating to size, shape, action, location, their orientation, and their number of heads. Broadly there are two types of muscle fiber: Type I , which is slow, and Type II which are fast. Type II has two divisions of type IIA (oxidative), and type IIX (glycolytic), giving three main fiber types. These fibers have relatively distinct metabolic, contractile, and motor unit properties. The table below differentiates these types of properties. These types of properties—while they are partly dependent on
2475-458: A long term system of aerobic energy transfer. These mainly include the ATPase type I and MHC type I fibers. They tend to have a low activity level of ATPase, a slower speed of contraction with a less well developed glycolytic capacity. Fibers that become slow-twitch develop greater numbers of mitochondria and capillaries making them better for prolonged work. Individual muscles tend to be
2640-417: A mixture of various fiber types, but their proportions vary depending on the actions of that muscle. For instance, in humans, the quadriceps muscles contain ~52% type I fibers, while the soleus is ~80% type I. The orbicularis oculi muscle of the eye is only ~15% type I. Motor units within the muscle, however, have minimal variation between the fibers of that unit. It is this fact that makes
2805-452: A more specialized question is how to square the subjective notion that we are in control of our decisions (at least in some small measure) with the customary view of causality that subsequent events are caused by prior events. The topic of free will is the philosophical and scientific examination of this conundrum. Many philosophers consider experience to be the essence of consciousness, and believe that experience can only fully be known from
2970-468: A muscle, and are often termed as muscle fibers . A single muscle such as the biceps in a young adult male contains around 253,000 muscle fibers. Skeletal muscle fibers are multinucleated with the nuclei often referred to as myonuclei . This occurs during myogenesis with the fusion of myoblasts each contributing a nucleus. Fusion depends on muscle-specific proteins known as fusogens called myomaker and myomerger . Many nuclei are needed by
3135-456: A number of different environmental factors. This plasticity can, arguably, be the strongest evolutionary advantage among organisms with muscle. In fish, different fiber types are expressed at different water temperatures. Cold temperatures require more efficient metabolism within muscle and fatigue resistance is important. While in more tropical environments, fast powerful movements (from higher fast-twitch proportions) may prove more beneficial in
3300-417: A particular frequency corresponds to various points in the sleep-wake cycle, such as being asleep, being awake, or falling asleep. Alpha, beta, theta, gamma, and delta waves are all seen in the different stages of sleep. Each waveform maintains a different frequency and amplitude. Alpha waves are seen when a person is in a resting state, but is still fully conscious. Their eyes may be closed and all of their body
3465-463: A reliance on glycolytic enzymes. Fibers can also be classified on their twitch capabilities, into fast and slow twitch. These traits largely, but not completely, overlap the classifications based on color, ATPase, or MHC ( myosin heavy chain ). Some authors define a fast twitch fiber as one in which the myosin can split ATP very quickly. These mainly include the ATPase type II and MHC type II fibers. However, fast twitch fibers also demonstrate
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#17328511431833630-443: A screen before bed may interfere with sleep. Modern humans often find themselves desynchronized from their internal circadian clock, due to the requirements of work (especially night shifts ), long-distance travel, and the influence of universal indoor lighting. Even if they have sleep debt, or feel sleepy, people can have difficulty staying asleep at the peak of their circadian cycle. Conversely, they can have difficulty waking up in
3795-438: A set of rituals such as reading a bedtime story, a bath, brushing teeth, and can also include a show of affection from the parent to the child such a hug or kiss before bed. A bedtime routine will also include a consistent time that the child is expected to be in bed ready for sleep. Having a reliable bedtime routine can help improve a child's quality of sleep as well as prepare them to make and keep healthy sleep hygiene habits in
3960-493: A strong intuition for the existence of what they refer to as consciousness, skeptics argue that this intuition is too narrow, either because the concept of consciousness is embedded in our intuitions, or because we all are illusions. Gilbert Ryle , for example, argued that traditional understanding of consciousness depends on a Cartesian dualist outlook that improperly distinguishes between mind and body, or between mind and world. He proposed that we speak not of minds, bodies, and
4125-609: A subjective point of view. Objective sleep quality refers to how difficult it is for a person to fall asleep and remain in a sleeping state, and how many times they wake up during a single night. Poor sleep quality disrupts the cycle of transition between the different stages of sleep. Subjective sleep quality in turn refers to a sense of being rested and regenerated after awaking from sleep. A study by A. Harvey et al. (2002) found that insomniacs were more demanding in their evaluations of sleep quality than individuals who had no sleep problems. Homeostatic sleep propensity (the need for sleep as
4290-483: A tendon. Multipennate muscles have fibers that are oriented at multiple angles along the force-generating axis, and this is the most general and most common architecture. Muscle fibers grow when exercised and shrink when not in use. This is due to the fact that exercise stimulates the increase in myofibrils which increase the overall size of muscle cells. Well exercised muscles can not only add more size but can also develop more mitochondria , myoglobin , glycogen and
4455-537: A transitional period is called slow-wave sleep or deep sleep. During this phase, body temperature and heart rate fall, and the brain uses less energy. REM sleep, also known as paradoxical sleep, represents a smaller portion of total sleep time. It is the main occasion for dreams (or nightmares ), and is associated with desynchronized and fast brain waves, eye movements, loss of muscle tone, and suspension of homeostasis . The sleep cycle of alternate NREM and REM sleep takes an average of 90 minutes, occurring 4–6 times in
4620-519: Is adenosine , a neurotransmitter that inhibits many of the bodily processes associated with wakefulness. Adenosine levels increase in the cortex and basal forebrain during prolonged wakefulness, and decrease during the sleep-recovery period, potentially acting as a homeostatic regulator of sleep. Coffee , tea, and other sources of caffeine temporarily block the effect of adenosine, prolong sleep latency, and reduce total sleep time and quality. Humans are also influenced by aspects of social time , such as
4785-406: Is awareness of internal and external existence . However, its nature has led to millennia of analyses, explanations, and debate by philosophers , scientists , and theologians . Opinions differ about what exactly needs to be studied or even considered consciousness. In some explanations, it is synonymous with the mind , and at other times, an aspect of it. In the past, it was one's "inner life",
4950-421: Is a common synonym for all forms of awareness, or simply ' experience ', without differentiating between inner and outer, or between higher and lower types. With advances in brain research, "the presence or absence of experienced phenomena " of any kind underlies the work of those neuroscientists who seek "to analyze the precise relation of conscious phenomenology to its associated information processing" in
5115-400: Is a predominance of type II fibers utilizing glycolytic metabolism. Because of the discrepancy in fast twitch fibers compared to humans, chimpanzees outperform humans in power related tests. Humans, however, will do better at exercise in aerobic range requiring large metabolic costs such as walking (bipedalism). Across species, certain gene sequences have been preserved, but do not always have
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5280-405: Is a slow twitch-fiber that can sustain longer contractions ( tonic ). In lobsters, muscles in different body parts vary in the muscle fiber type proportions based on the purpose of the muscle group. In the early development of vertebrate embryos, growth and formation of muscle happens in successive waves or phases of myogenesis . The myosin heavy chain isotype is a major determinant of
5445-450: Is access conscious; when we introspect , information about our thoughts is access conscious; when we remember , information about the past is access conscious, and so on. Although some philosophers, such as Daniel Dennett , have disputed the validity of this distinction, others have broadly accepted it. David Chalmers has argued that A-consciousness can in principle be understood in mechanistic terms, but that understanding P-consciousness
5610-550: Is accumulated against an individual's average sleep or some other benchmark. It is also unclear whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. Sleep debt does show some evidence of being cumulative. Subjectively, however, humans seem to reach maximum sleepiness 30 hours after waking. It is likely that in Western societies , children are sleeping less than they previously have. One neurochemical indicator of sleep debt
5775-616: Is also debate over whether or not A-consciousness and P-consciousness always coexist or if they can exist separately. Although P-consciousness without A-consciousness is more widely accepted, there have been some hypothetical examples of A without P. Block, for instance, suggests the case of a " zombie " that is computationally identical to a person but without any subjectivity. However, he remains somewhat skeptical concluding "I don't know whether there are any actual cases of A-consciousness without P-consciousness, but I hope I have illustrated their conceptual possibility". Sam Harris observes: "At
5940-499: Is attached to other organelles such as the mitochondria by intermediate filaments in the cytoskeleton. The costamere attaches the sarcomere to the sarcolemma. Every single organelle and macromolecule of a muscle fiber is arranged to ensure that it meets desired functions. The cell membrane is called the sarcolemma with the cytoplasm known as the sarcoplasm . In the sarcoplasm are the myofibrils. The myofibrils are long protein bundles about one micrometer in diameter. Pressed against
6105-681: Is central to the animal rights movement , because it includes the ability to experience pain and suffering. For many decades, consciousness as a research topic was avoided by the majority of mainstream scientists, because of a general feeling that a phenomenon defined in subjective terms could not properly be studied using objective experimental methods. In 1975 George Mandler published an influential psychological study which distinguished between slow, serial, and limited conscious processes and fast, parallel and extensive unconscious ones. The Science and Religion Forum 1984 annual conference, ' From Artificial Intelligence to Human Consciousness ' identified
6270-649: Is dark. The diverse purposes and mechanisms of sleep are the subject of substantial ongoing research. Sleep is a highly conserved behavior across animal evolution, likely going back hundreds of millions of years. Humans may suffer from various sleep disorders , including dyssomnias , such as insomnia , hypersomnia , narcolepsy , and sleep apnea ; parasomnias , such as sleepwalking and rapid eye movement sleep behavior disorder ; bruxism ; and circadian rhythm sleep disorders . The use of artificial light has substantially altered humanity's sleep patterns. Common sources of artificial light include outdoor lighting and
6435-496: Is defined roughly like English "consciousness" 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". About forty meanings attributed to the term consciousness can be identified and categorized based on functions and experiences . The prospects for reaching any single, agreed-upon, theory-independent definition of consciousness appear remote. Scholars are divided as to whether Aristotle had
6600-505: Is expressed in other mammals, so is still accurately seen (along with IIB) in the literature. Non human fiber types include true IIb fibers, IIc, IId, etc. Further fiber typing methods are less formally delineated, and exist on more of a spectrum. They tend to be focused more on metabolic and functional capacities (i.e., oxidative vs. glycolytic , fast vs. slow contraction time). As noted above, fiber typing by ATPase or MHC does not directly measure or dictate these parameters. However, many of
6765-481: Is generally taken to be the first philosopher to use conscientia in a way less like the traditional meaning and more like the way modern English speakers would use "conscience", his meaning is nowhere defined. In Search after Truth ( Regulæ ad directionem ingenii ut et inquisitio veritatis per lumen naturale , Amsterdam 1701) he wrote the word with a gloss : conscientiâ, vel interno testimonio (translatable as "conscience, or internal testimony"). It might mean
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6930-613: Is intrinsically incapable of explaining the holistic aspects of consciousness, but that quantum theory may provide the missing ingredients. Several theorists have therefore proposed quantum mind (QM) theories of consciousness. Notable theories falling into this category include the holonomic brain theory of Karl Pribram and David Bohm , and the Orch-OR theory formulated by Stuart Hameroff and Roger Penrose . Some of these QM theories offer descriptions of phenomenal consciousness, as well as QM interpretations of access consciousness. None of
7095-399: Is isolated in a bunker with constant light or darkness, he or she will continue to experience rhythmic increases and decreases of body temperature and melatonin, on a period that slightly exceeds 24 hours. Scientists refer to such conditions as free-running of the circadian rhythm. Under natural conditions, light signals regularly adjust this period downward, so that it corresponds better with
7260-445: Is known as a "natural short sleeper". This condition is not to be confused with intentional sleep deprivation, which leaves symptoms such as irritability or temporarily impaired cognitive abilities in people who are predisposed to sleep a normal amount of time but not in people with FNSS. The genes DEC2 , ADRB1 , NPSR1 and GRM1 are implicated in enabling short sleep. The quality of sleep may be evaluated from an objective and
7425-470: Is linked to some kind of "selfhood", for example to certain pragmatic issues such as the feeling of agency and the effects of regret and action on experience of one's own body or social identity. Similarly Daniel Kahneman , who focused on systematic errors in perception, memory and decision-making, has differentiated between two kinds of mental processes, or cognitive "systems": the "fast" activities that are primary, automatic and "cannot be turned off", and
7590-454: Is merely an illusion), and neutral monism (which holds that both mind and matter are aspects of a distinct essence that is itself identical to neither of them). There are also, however, a large number of idiosyncratic theories that cannot cleanly be assigned to any of these schools of thought. Since the dawn of Newtonian science with its vision of simple mechanical principles governing the entire universe, some philosophers have been tempted by
7755-585: Is much more challenging: he calls this the hard problem of consciousness . Some philosophers believe that Block's two types of consciousness are not the end of the story. William Lycan , for example, argued in his book Consciousness and Experience that at least eight clearly distinct types of consciousness can be identified (organism consciousness; control consciousness; consciousness of ; state/event consciousness; reportability; introspective consciousness; subjective consciousness; self-consciousness)—and that even this list omits several more obscure forms. There
7920-457: Is not a simple matter: If awareness of the environment . . . is the criterion of consciousness, then even the protozoans are conscious. If awareness of awareness is required, then it is doubtful whether the great apes and human infants are conscious. Many philosophers have argued that consciousness is a unitary concept that is understood by the majority of people despite the difficulty philosophers have had defining it. Max Velmans proposed that
8085-454: Is not necessary to explain what we observe. Some philosophers, such as Daniel Dennett in a research paper titled "The Unimagined Preposterousness of Zombies", argue that people who give this explanation do not really understand what they are saying. More broadly, philosophers who do not accept the possibility of zombies generally believe that consciousness is reflected in behavior (including verbal behavior), and that we attribute consciousness on
8250-399: Is not the same as ATPase fiber typing. Almost all multicellular animals depend on muscles to move. Generally, muscular systems of most multicellular animals comprise both slow-twitch and fast-twitch muscle fibers, though the proportions of each fiber type can vary across organisms and environments. The ability to shift their phenotypic fiber type proportions through training and responding to
8415-444: Is now the dominant position among contemporary philosophers of mind. For an overview of the field, approaches often include both historical perspectives (e.g., Descartes, Locke, Kant ) and organization by key issues in contemporary debates. An alternative is to focus primarily on current philosophical stances and empirical Philosophers differ from non-philosophers in their intuitions about what consciousness is. While most people have
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#17328511431838580-420: Is observed to be a necessary behavior across most of the animal kingdom, including some of the least cognitively advanced animals which have no need for other functions of sleep, such as memory consolidation or dreaming. It has been widely accepted that sleep must support the formation of long-term memory, and generally increasing previous learning and experiences recalls. However, its benefit seems to depend on
8745-518: Is physically indistinguishable from a human being and behaves like a human being in every way but nevertheless lacks consciousness. Related issues have also been studied extensively by Greg Littmann of the University of Illinois, and by Colin Allen (a professor at the University of Pittsburgh) regarding the literature and research studying artificial intelligence in androids. The most commonly given answer
8910-404: Is preceded by the formation of connective tissue frameworks, usually formed from the somatic lateral plate mesoderm . Myoblasts follow chemical signals to the appropriate locations, where they fuse into elongated multinucleated skeletal muscle cells. Between the tenth and the eighteenth weeks of gestation, all muscle cells have fast myosin heavy chains; two myotube types become distinguished in
9075-441: Is profoundly influenced by changes in light, since these are its main clues about what time it is. Exposure to even small amounts of light during the night can suppress melatonin secretion, and increase body temperature and wakefulness. Short pulses of light, at the right moment in the circadian cycle, can significantly 'reset' the internal clock. Blue light, in particular, exerts the strongest effect, leading to concerns that use of
9240-445: Is raw experience: it is moving, colored forms, sounds, sensations, emotions and feelings with our bodies and responses at the center. These experiences, considered independently of any impact on behavior, are called qualia . A-consciousness, on the other hand, is the phenomenon whereby information in our minds is accessible for verbal report, reasoning, and the control of behavior. So, when we perceive , information about what we perceive
9405-399: Is regulated by a process called homeostasis . Induced or perceived lack of sleep is called sleep deprivation . Process S is driven by the depletion of glycogen and accumulation of adenosine in the forebrain that disinhibits the ventrolateral preoptic nucleus , allowing for inhibition of the ascending reticular activating system . Sleep deprivation tends to cause slower brain waves in
9570-443: Is resting and relatively still, where the body is starting to slow down. Beta waves take over alpha waves when a person is at attention, as they might be completing a task or concentrating on something. Beta waves consist of the highest of frequencies and the lowest of amplitude, and occur when a person is fully alert. Gamma waves are seen when a person is highly focused on a task or using all their concentration. Theta waves occur during
9735-572: Is surrounded by a type of connective tissue layer of fascia . Muscle fibers are formed from the fusion of developmental myoblasts in a process known as myogenesis resulting in long multinucleated cells. In these cells the nuclei , termed myonuclei , are located along the inside of the cell membrane . Muscle fibers also have multiple mitochondria to meet energy needs. Muscle fibers are in turn composed of myofibrils . The myofibrils are composed of actin and myosin filaments called myofilaments , repeated in units called sarcomeres, which are
9900-428: Is that we attribute consciousness to other people because we see that they resemble us in appearance and behavior; we reason that if they look like us and act like us, they must be like us in other ways, including having experiences of the sort that we do. There are, however, a variety of problems with that explanation. For one thing, it seems to violate the principle of parsimony , by postulating an invisible entity that
10065-409: Is the fact that consciousness of some sort goes on. 'States of mind' succeed each other in him . [...] But everyone knows what the terms mean [only] in a rough way; [...] When I say every 'state' or 'thought' is part of a personal consciousness , 'personal consciousness' is one of the terms in question. Its meaning we know so long as no one asks us to define it, but to give an accurate account of it
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#173285114318310230-438: Is the most difficult of philosophic tasks. [...] The only states of consciousness that we naturally deal with are found in personal consciousnesses, minds, selves, concrete particular I's and you's. Prior to the 20th century, philosophers treated the phenomenon of consciousness as the "inner world [of] one's own mind", and introspection was the mind "attending to" itself, an activity seemingly distinct from that of perceiving
10395-454: Is used in fiber typing vs. MHC typing, and some ATPase types actually contain multiple MHC types. Also, a subtype B or b is not expressed in humans by either method . Early researchers believed humans to express a MHC IIb, which led to the ATPase classification of IIB. However, later research showed that the human MHC IIb was in fact IIx, indicating that the IIB is better named IIX. IIb
10560-486: The unconscious processes of cognition such as perception , reactive awareness and attention , and automatic forms of learning , problem-solving , and decision-making . The cognitive science point of view—with an inter-disciplinary perspective involving fields such as psychology , linguistics and anthropology —requires no agreed definition of "consciousness" but studies the interaction of many processes besides perception. For some researchers, consciousness
10725-625: The Journal of Consciousness Studies , along with regular conferences organized by groups such as the Association for the Scientific Study of Consciousness and the Society for Consciousness Studies . Skeletal muscle Skeletal muscle (commonly referred to as muscle ) is one of the three types of vertebrate muscle tissue , the other being cardiac muscle and smooth muscle . They are part of
10890-575: The Zhuangzi. This bird's name is Of a Flock ( peng 鵬 ), yet its back is countless thousands of miles across and its wings are like clouds arcing across the heavens. "Like Of a Flock, whose wings arc across the heavens, the wings of your consciousness span to the horizon. At the same time, the wings of every other being's consciousness span to the horizon. You are of a flock, one bird among kin." Mental processes (such as consciousness) and physical processes (such as brain events) seem to be correlated, however
11055-486: The circadian clock (Process C), sleep-wake homeostasis (Process S), and to some extent by the individual will. Sleep timing depends greatly on hormonal signals from the circadian clock, or Process C, a complex neurochemical system which uses signals from an organism's environment to recreate an internal day–night rhythm. Process C counteracts the homeostatic drive for sleep during the day (in diurnal animals) and augments it at night. The suprachiasmatic nucleus (SCN),
11220-449: The erector spinae and small vertebral muscles, and are innervated by the dorsal rami of the spinal nerves . All other muscles, including those of the limbs are hypaxial, and innervated by the ventral rami of the spinal nerves. During development, myoblasts (muscle progenitor cells) either remain in the somite to form muscles associated with the vertebral column or migrate out into the body to form all other muscles. Myoblast migration
11385-435: The frontal cortex , shortened attention span, higher anxiety, impaired memory, and a grouchy mood. Conversely, a well-rested organism tends to have improved memory and mood. Neurophysiological and functional imaging studies have demonstrated that frontal regions of the brain are particularly responsive to homeostatic sleep pressure. There is disagreement on how much sleep debt is possible to accumulate, and whether sleep debt
11550-430: The mind during certain stages of sleep. During sleep, most of the body's systems are in an anabolic state, helping to restore the immune , nervous , skeletal , and muscular systems; these are vital processes that maintain mood , memory , and cognitive function , and play a large role in the function of the endocrine and immune systems . The internal circadian clock promotes sleep daily at night , when it
11715-458: The pectoral , and abdominal muscles ; intrinsic and extrinsic muscles are subdivisions of muscle groups in the hand , foot , tongue , and extraocular muscles of the eye . Muscles are also grouped into compartments including four groups in the arm , and the four groups in the leg . Apart from the contractile part of a muscle consisting of its fibers, a muscle contains a non-contractile part of dense fibrous connective tissue that makes up
11880-580: The sarcolemma . The myonuclei are quite uniformly arranged along the fiber with each nucleus having its own myonuclear domain where it is responsible for supporting the volume of cytoplasm in that particular section of the myofiber. A group of muscle stem cells known as myosatellite cells , also satellite cells are found between the basement membrane and the sarcolemma of muscle fibers. These cells are normally quiescent but can be activated by exercise or pathology to provide additional myonuclei for muscle growth or repair. Muscles attach to tendons in
12045-436: The tendon at each end. The tendons attach the muscles to bones to give skeletal movement. The length of a muscle includes the tendons. Connective tissue is present in all muscles as deep fascia . Deep fascia specialises within muscles to enclose each muscle fiber as endomysium ; each muscle fascicle as perimysium , and each individual muscle as epimysium . Together these layers are called mysia . Deep fascia also separates
12210-465: The voluntary muscular system and typically are attached by tendons to bones of a skeleton . The skeletal muscle cells are much longer than in the other types of muscle tissue, and are also known as muscle fibers . The tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres . A skeletal muscle contains multiple fascicles – bundles of muscle fibers. Each individual fiber, and each muscle
12375-619: The "contents of conscious experience by introspection and experiment ". Another popular metaphor was James's doctrine of the stream of consciousness , with continuity, fringes, and transitions. James discussed the difficulties of describing and studying psychological phenomena, recognizing that commonly-used terminology was a necessary and acceptable starting point towards more precise, scientifically justified language. Prime examples were phrases like inner experience and personal consciousness : The first and foremost concrete fact which every one will affirm to belong to his inner experience
12540-439: The "everyday understanding of consciousness" uncontroversially "refers to experience itself rather than any particular thing that we observe or experience" and he added that consciousness "is [therefore] exemplified by all the things that we observe or experience", whether thoughts, feelings, or perceptions. Velmans noted however, as of 2009, that there was a deep level of "confusion and internal division" among experts about
12705-485: The "slow", deliberate, effortful activities of a secondary system "often associated with the subjective experience of agency, choice, and concentration". Kahneman's two systems have been described as "roughly corresponding to unconscious and conscious processes". The two systems can interact, for example in sharing the control of attention. While System 1 can be impulsive, "System 2 is in charge of self-control", and "When we think of ourselves, we identify with System 2,
12870-464: The "structure" of the mind by analyzing its "elements". The abstract idea of states of consciousness mirrored the concept of states of matter . In 1892, William James noted that the "ambiguous word 'content' has been recently invented instead of 'object'" and that the metaphor of mind as a container seemed to minimize the dualistic problem of how "states of consciousness can know " things, or objects; by 1899 psychologists were busily studying
13035-456: The 'outer world' and its physical phenomena. In 1892 William James noted the distinction along with doubts about the inward character of the mind: 'Things' have been doubted, but thoughts and feelings have never been doubted. The outer world, but never the inner world, has been denied. Everyone assumes that we have direct introspective acquaintance with our thinking activity as such, with our consciousness as something inward and contrasted with
13200-547: The 17th century, and the first recorded use of "conscious" as a simple adjective was applied figuratively to inanimate objects ( "the conscious Groves" , 1643). It derived from the Latin conscius ( con- "together" and scio "to know") which meant "knowing with" or "having joint or common knowledge with another", especially as in sharing a secret. Thomas Hobbes in Leviathan (1651) wrote: "Where two, or more men, know of one and
13365-438: The associated related changes, not a change in fiber type. There are numerous methods employed for fiber-typing, and confusion between the methods is common among non-experts. Two commonly confused methods are histochemical staining for myosin ATPase activity and immunohistochemical staining for myosin heavy chain (MHC) type. Myosin ATPase activity is commonly—and correctly—referred to as simply "fiber type", and results from
13530-443: The basic functional, contractile units of the muscle fiber necessary for muscle contraction . Muscles are predominantly powered by the oxidation of fats and carbohydrates , but anaerobic chemical reactions are also used, particularly by fast twitch fibers . These chemical reactions produce adenosine triphosphate (ATP) molecules that are used to power the movement of the myosin heads . Skeletal muscle comprises about 35% of
13695-448: The basis of behavior. A more straightforward way of saying this is that we attribute experiences to people because of what they can do , including the fact that they can tell us about their experiences. The term " qualia " was introduced in philosophical literature by C. I. Lewis . The word is derived from Latin and means "of what sort". It is basically a quantity or property of something as perceived or experienced by an individual, like
13860-668: The body of humans by weight. The functions of skeletal muscle include producing movement, maintaining body posture, controlling body temperature, and stabilizing joints. Skeletal muscle is also an endocrine organ . Under different physiological conditions, subsets of 654 different proteins as well as lipids, amino acids, metabolites and small RNAs are found in the secretome of skeletal muscles. Skeletal muscles are substantially composed of multinucleated contractile muscle fibers (myocytes). However, considerable numbers of resident and infiltrating mononuclear cells are also present in skeletal muscles. In terms of volume, myocytes make up
14025-591: The body surface" invites another criticism, that most consciousness research since the 1990s, perhaps because of bias, has focused on processes of external perception . From a history of psychology perspective, Julian Jaynes rejected popular but "superficial views of consciousness" especially those which equate it with "that vaguest of terms, experience ". In 1976 he insisted that if not for introspection , which for decades had been ignored or taken for granted rather than explained, there could be no "conception of what consciousness is" and in 1990, he reaffirmed
14190-412: The brain and body, the reduced rate of metabolism enables countervailing restorative processes. The brain requires sleep for restoration, whereas these processes can take place during quiescent waking in the rest of the body. The essential function of sleep may be its restorative effect on the brain: "Sleep is of the brain, by the brain and for the brain." This theory is strengthened by the fact that sleep
14355-463: The brain from metabolic end products generated during waking. Anabolic hormones, such as growth hormones , are secreted preferentially during sleep. The brain concentration of glycogen increases during sleep, and is depleted through metabolism during wakefulness. The human organism physically restores itself during sleep, occurring mostly during slow-wave sleep during which body temperature, heart rate, and brain oxygen consumption decrease. In both
14520-556: The brain restores its supply of adenosine triphosphate (ATP), the molecule used for short-term storage and transport of energy. In quiet waking, the brain is responsible for 20% of the body's energy use, thus this reduction has a noticeable effect on overall energy consumption. Sleep increases the sensory threshold . In other words, sleeping persons perceive fewer stimuli, but can generally still respond to loud noises and other salient sensory events. During slow-wave sleep , humans secrete bursts of growth hormone . All sleep, even during
14685-408: The brain. This neuroscientific goal is to find the "neural correlates of consciousness" (NCC). One criticism of this goal is that it begins with a theoretical commitment to the neurological origin of all "experienced phenomena" whether inner or outer. Also, the fact that the easiest 'content of consciousness' to be so analyzed is "the experienced three-dimensional world (the phenomenal world) beyond
14850-436: The brain. Many other neuroscientists, such as Christof Koch , have explored the neural basis of consciousness without attempting to frame all-encompassing global theories. At the same time, computer scientists working in the field of artificial intelligence have pursued the goal of creating digital computer programs that can simulate or embody consciousness . A few theoretical physicists have argued that classical physics
15015-637: The conscious, reasoning self that has beliefs, makes choices, and decides what to think about and what to do". Some have argued that we should eliminate the concept from our understanding of the mind, a position known as consciousness semanticism. In medicine , a "level of consciousness" terminology is used to describe a patient's arousal and responsiveness, which can be seen as a continuum of states ranging from full alertness and comprehension , through disorientation, delirium , loss of meaningful communication, and finally loss of movement in response to painful stimuli . Issues of practical concern include how
15180-650: The day, is associated with the secretion of prolactin . Key physiological methods for monitoring and measuring changes during sleep include electroencephalography (EEG) of brain waves , electrooculography (EOG) of eye movements, and electromyography (EMG) of skeletal muscle activity. Simultaneous collection of these measurements is called polysomnography , and can be performed in a specialized sleep laboratory . Sleep researchers also use simplified electrocardiography (EKG) for cardiac activity and actigraphy for motor movements. The electrical activity seen on an EEG represents brain waves. The amplitude of EEG waves at
15345-920: The deepest period of sleep. Napping too long and entering the slow wave cycles can make it difficult to awake from the nap and leave one feeling unrested. This period of drowsiness is called sleep inertia . The siesta habit has recently been associated with a 37% lower coronary mortality, possibly due to reduced cardiovascular stress mediated by daytime sleep. Short naps at mid-day and mild evening exercise were found to be effective for improved sleep, cognitive tasks, and mental health in elderly people. Monozygotic (identical) but not dizygotic (fraternal) twins tend to have similar sleep habits. Neurotransmitters, molecules whose production can be traced to specific genes, are one genetic influence on sleep that can be analyzed. The circadian clock has its own set of genes. Genes which may influence sleep include ABCC9 , DEC2 , Dopamine receptor D2 and variants near PAX 8 and VRK2 . While
15510-422: The difficulty of producing a definition that does not involve circularity or fuzziness. In The Macmillan Dictionary of Psychology (1989 edition), Stuart Sutherland emphasized external awareness, and expressed a skeptical attitude more than a definition: Consciousness —The having of perceptions, thoughts, and feelings ; awareness. The term is impossible to define except in terms that are unintelligible without
15675-542: The direct assaying of ATPase activity under various conditions (e.g. pH ). Myosin heavy chain staining is most accurately referred to as "MHC fiber type", e.g. "MHC IIa fibers", and results from determination of different MHC isoforms . These methods are closely related physiologically, as the MHC type is the primary determinant of ATPase activity. However, neither of these typing methods is directly metabolic in nature; they do not directly address oxidative or glycolytic capacity of
15840-724: The distinction between inward awareness and perception of the physical world, or the distinction between conscious and unconscious , or the notion of a mental entity or mental activity that is not physical. The common-usage definitions of consciousness in Webster's Third New International Dictionary (1966) are as follows: The Cambridge English Dictionary defines consciousness as "the state of understanding and realizing something". The Oxford Living Dictionary defines consciousness as "[t]he state of being aware of and responsive to one's surroundings", "[a] person's awareness or perception of something", and "[t]he fact of awareness by
16005-504: The end of the dark time. Bimodal sleep in humans was more common before the Industrial Revolution . Different characteristic sleep patterns, such as the familiarly so-called " early bird " and " night owl ", are called chronotypes . Genetics and sex have some influence on chronotype, but so do habits. Chronotype is also liable to change over the course of a person's lifetime. Seven-year-olds are better disposed to wake up early in
16170-556: The end of the sleep cycle. Awakening involves heightened electrical activation in the brain, beginning with the thalamus and spreading throughout the cortex . On a typical night of sleep, there is not much time that is spent in the waking state. In various sleep studies that have been conducted using the electroencephalography, it has been found that females are awake for 0-1% during their nightly sleep while males are awake for 0-2% during that time. In adults, wakefulness increases, especially in later cycles. One study found 3% awake time in
16335-531: The environment has served organisms well when placed in changing environments either requiring short explosive movements (higher fast twitch proportion) or long duration of movement (higher slow twitch proportion) to survive. Bodybuilding has shown that changes in muscle mass and force production can change in a matter of months. Some examples of this variation are described below. American lobster , Homarus americanus , has three fiber types including fast twitch fibers, slow-twitch and slow-tonic fibers. Slow-tonic
16500-480: The exact 24 hours of an Earth day. The circadian clock exerts constant influence on the body, affecting sinusoidal oscillation of body temperature between roughly 36.2 °C and 37.2 °C. The suprachiasmatic nucleus itself shows conspicuous oscillation activity, which intensifies during subjective day (i.e., the part of the rhythm corresponding with daytime, whether accurately or not) and drops to almost nothing during subjective night. The circadian pacemaker in
16665-399: The fascicles can vary in their relationship to one another, and to their tendons. These variations are seen in fusiform , strap , and convergent muscles . A convergent muscle has a triangular or fan-shape as the fibers converge at its insertion and are fanned out broadly at the origin. A less common example of a parallel muscle is a circular muscle such as the orbicularis oculi , in which
16830-438: The fiber. When "type I" or "type II" fibers are referred to generically, this most accurately refers to the sum of numerical fiber types (I vs. II) as assessed by myosin ATPase activity staining (e.g. "type II" fibers refers to type IIA + type IIAX + type IIXA ... etc.). Below is a table showing the relationship between these two methods, limited to fiber types found in humans. Subtype capitalization
16995-461: The fibers are longitudinally arranged, but create a circle from origin to insertion. These different architectures, can cause variations in the tension that a muscle can create between its tendons. The fibers in pennate muscles run at an angle to the axis of force generation. This pennation angle reduces the effective force of any individual fiber, as it is effectively pulling off-axis. However, because of this angle, more fibers can be packed into
17160-593: The fibers of a skeletal muscle. It is thought that by performing endurance type events for a sustained period of time, some of the type IIX fibers transform into type IIA fibers. However, there is no consensus on the subject. It may well be that the type IIX fibers show enhancements of the oxidative capacity after high intensity endurance training which brings them to a level at which they are able to perform oxidative metabolism as effectively as slow twitch fibers of untrained subjects. This would be brought about by an increase in mitochondrial size and number and
17325-528: The first ninety-minute sleep cycle, 8% in the second, 10% in the third, 12% in the fourth, and 13–14% in the fifth. Most of this awake time occurred shortly after REM sleep. Today, many humans wake up with an alarm clock ; however, people can also reliably wake themselves up at a specific time with no need for an alarm. Many sleep quite differently on workdays versus days off, a pattern which can lead to chronic circadian desynchronization. Many people regularly look at television and other screens before going to bed,
17490-467: The following example: It is difficult for modern Western man to grasp that the Greeks really had no concept of consciousness in that they did not class together phenomena as varied as problem solving, remembering, imagining, perceiving, feeling pain, dreaming, and acting on the grounds that all these are manifestations of being aware or being conscious. Many philosophers and scientists have been unhappy about
17655-515: The future. Children need many hours of sleep per day in order to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages. Early in 2015, after a two-year study, the National Sleep Foundation in the US announced newly revised recommendations as shown in the table below. Sleep may facilitate the synthesis of molecules that help repair and protect
17820-510: The great majority of skeletal muscle. Skeletal muscle myocytes are usually very large, being about 2–3 cm long and 100 μm in diameter. By comparison, the mononuclear cells in muscles are much smaller. Some of the mononuclear cells in muscles are endothelial cells (which are about 50–70 μm long, 10–30 μm wide and 0.1–10 μm thick), macrophages (21 μm in diameter) and neutrophils (12-15 μm in diameter). However, in terms of nuclei present in skeletal muscle, myocyte nuclei may be only half of
17985-403: The groups of muscles into muscle compartments. Two types of sensory receptors found in muscles are muscle spindles , and Golgi tendon organs . Muscle spindles are stretch receptors located in the muscle belly. Golgi tendon organs are proprioceptors located at the myotendinous junction that inform of a muscle's tension . Skeletal muscle cells are the individual contractile cells within
18150-467: The higher end of any sport tend to demonstrate patterns of fiber distribution e.g. endurance athletes show a higher level of type I fibers. Sprint athletes, on the other hand, require large numbers of type IIX fibers. Middle-distance event athletes show approximately equal distribution of the two types. This is also often the case for power athletes such as throwers and jumpers. It has been suggested that various types of exercise can induce changes in
18315-407: The highest rate of sleep. The hours that children spend asleep influence their ability to perform on cognitive tasks. Children who sleep through the night and have few night waking episodes have higher cognitive attainments and easier temperaments than other children. Sleep also influences language development. To test this, researchers taught infants a faux language and observed their recollection of
18480-445: The hormone melatonin, and minimum core body temperature. Human sleep-needs vary by age and amongst individuals; sleep is considered to be adequate when there is no daytime sleepiness or dysfunction. Moreover, self-reported sleep duration is only moderately correlated with actual sleep time as measured by actigraphy , and those affected with sleep state misperception may typically report having slept only four hours despite having slept
18645-474: The hours when other people are awake, the hours when work is required, the time on clocks, etc. Time zones , standard times used to unify the timing for people in the same area, correspond only approximately to the natural rising and setting of the sun. An extreme example of the approximate nature of time zones is China, a country which used to span five time zones and now officially uses only one (UTC+8). In polyphasic sleep , an organism sleeps several times in
18810-405: The human body, making up around 40% of body weight in healthy young adults. In Western populations, men have on average around 61% more skeletal muscle than women. Most muscles occur in bilaterally-placed pairs to serve both sides of the body. Muscles are often classed as groups of muscles that work together to carry out an action. In the torso there are several major muscle groups including
18975-581: The idea that consciousness could be explained in purely physical terms. The first influential writer to propose such an idea explicitly was Julien Offray de La Mettrie , in his book Man a Machine ( L'homme machine ). His arguments, however, were very abstract. The most influential modern physical theories of consciousness are based on psychology and neuroscience . Theories proposed by neuroscientists such as Gerald Edelman and Antonio Damasio , and by philosophers such as Daniel Dennett, seek to explain consciousness in terms of neural events occurring within
19140-432: The inside of the sarcolemma are the unusual flattened myonuclei. Between the myofibrils are the mitochondria . While the muscle fiber does not have smooth endoplasmic cisternae, it contains sarcoplasmic reticulum . The sarcoplasmic reticulum surrounds the myofibrils and holds a reserve of the calcium ions needed to cause a muscle contraction. Periodically, it has dilated end sacs known as terminal cisternae . These cross
19305-437: The inside, subjectively. The problem of other minds is a philosophical problem traditionally stated as the following epistemological question: Given that I can only observe the behavior of others, how can I know that others have minds? The problem of other minds is particularly acute for people who believe in the possibility of philosophical zombies , that is, people who think it is possible in principle to have an entity that
19470-590: The interaction between these two domains occurs inside the brain, perhaps in a small midline structure called the pineal gland . Although it is widely accepted that Descartes explained the problem cogently, few later philosophers have been happy with his solution, and his ideas about the pineal gland have especially been ridiculed. However, no alternative solution has gained general acceptance. Proposed solutions can be divided broadly into two categories: dualist solutions that maintain Descartes's rigid distinction between
19635-525: The knowledge of the value of one's own thoughts. The origin of the modern concept of consciousness is often attributed to John Locke who defined the word in his Essay Concerning Human Understanding , published in 1690, as "the perception of what passes in a man's own mind". The essay strongly influenced 18th-century British philosophy , and Locke's definition appeared in Samuel Johnson 's celebrated Dictionary (1755). The French term conscience
19800-489: The latter have been found in a GWAS study that primarily detects correlations (but not necessarily causation), other genes have been shown to have a more direct effect. For instance, mice lacking dihydropyrimidine dehydrogenase (Dpyd) had 78.4 min less sleep during the lights-off period than wild-type mice. Dpyd encodes the rate-limiting enzyme in the metabolic pathway that catabolizes uracil and thymidine to β- alanine , an inhibitory neurotransmitter . This also supports
19965-472: The level of consciousness can be assessed in severely ill, comatose, or anesthetized people, and how to treat conditions in which consciousness is impaired or disrupted. The degree or level of consciousness is measured by standardized behavior observation scales such as the Glasgow Coma Scale . While historically philosophers have defended various views on consciousness, surveys indicate that physicalism
20130-456: The level of your experience, you are not a body of cells, organelles, and atoms; you are consciousness and its ever-changing contents". Seen in this way, consciousness is a subjectively experienced, ever-present field in which things (the contents of consciousness) come and go. Christopher Tricker argues that this field of consciousness is symbolized by the mythical bird that opens the Daoist classic
20295-549: The long run. In rodents such as rats, the transitory nature of their muscle is highly prevalent. They have high percentage of hybrid muscle fibers and have up to 60% in fast-to-slow transforming muscle. Environmental influences such as diet, exercise and lifestyle types have a pivotal role in proportions of fiber type in humans. Aerobic exercise will shift the proportions towards slow twitch fibers, while explosive powerlifting and sprinting will transition fibers towards fast twitch. In animals, "exercise training" will look more like
20460-522: The mind of itself and the world". Philosophers have attempted to clarify technical distinctions by using a jargon of their own. The corresponding entry in the Routledge Encyclopedia of Philosophy (1998) reads: During the early 19th century, the emerging field of geology inspired a popular metaphor that the mind likewise had hidden layers "which recorded the past of the individual". By 1875, most psychologists believed that "consciousness
20625-493: The morning than are fifteen-year-olds. Chronotypes far outside the normal range are called circadian rhythm sleep disorders. Naps are short periods of sleep that one might take during the daytime, often in order to get the necessary amount of rest. Napping is often associated with childhood, but around one-third of American adults partake in it daily. The optimal nap duration is around 10–20 minutes, as researchers have proven that it takes at least 30 minutes to enter slow-wave sleep,
20790-438: The muscle fiber from one side to the other. In between two terminal cisternae is a tubular infolding called a transverse tubule (T tubule). T tubules are the pathways for action potentials to signal the sarcoplasmic reticulum to release calcium, causing a muscle contraction. Together, two terminal cisternae and a transverse tubule form a triad . All muscles are derived from paraxial mesoderm . During embryonic development in
20955-488: The nature of consciousness as a matter for investigation; Donald Michie was a keynote speaker. Starting in the 1980s, an expanding community of neuroscientists and psychologists have associated themselves with a field called Consciousness Studies , giving rise to a stream of experimental work published in books, journals such as Consciousness and Cognition , Frontiers in Consciousness Research , Psyche , and
21120-468: The neck that show a potential inverse trend of fiber type percentages (one muscle has high percentage of fast twitch, while the complementary muscle will have a higher percentage of slow twitch fibers). The complementary muscles of turtles had similar percentages of fiber types. Chimpanzee muscles are composed of 67% fast-twitch fibers and have a maximum dynamic force and power output 1.35 times higher than human muscles of similar size. Among mammals, there
21285-536: The need for long durations of movement or short explosive movements to escape predators or catch prey. Skeletal muscle exhibits a distinctive banding pattern when viewed under the microscope due to the arrangement of two contractile proteins myosin , and actin – that are two of the myofilaments in the myofibrils . The myosin forms the thick filaments, and actin forms the thin filaments, and are arranged in repeating units called sarcomeres . The interaction of both proteins results in muscle contraction. The sarcomere
21450-401: The night and density of eye movements. Sleep duration can also vary according to season. Up to 90% of people report longer sleep duration in winter, which may lead to more pronounced seasonal affective disorder . By the time infants reach the age of two, their brain size has reached 90 percent of an adult-sized brain; a majority of this brain growth has occurred during the period of life with
21615-404: The night. Circadian rhythm exerts some influence on the nighttime secretion of growth hormone. The circadian rhythm influences the ideal timing of a restorative sleep episode. Sleepiness increases during the night. REM sleep occurs more during body temperature minimum within the circadian cycle, whereas slow-wave sleep can occur more independently of circadian time. The internal circadian clock
21780-409: The notion of quantum consciousness, an experiment about wave function collapse led by Catalina Curceanu in 2022 suggests that quantum consciousness, as suggested by Roger Penrose and Stuart Hameroff , is highly implausible. Apart from the general question of the "hard problem" of consciousness (which is, roughly speaking, the question of how mental experience can arise from a physical basis ),
21945-491: The nuclei present, while nuclei from resident and infiltrating mononuclear cells make up the other half. Considerable research on skeletal muscle is focused on the muscle fiber cells, the myocytes, as discussed in detail in the first sections, below. However, recently, interest has also focused on the different types of mononuclear cells of skeletal muscle, as well as on the endocrine functions of muscle, described subsequently, below. There are more than 600 skeletal muscles in
22110-612: The others. Most skeletal muscles in a human contain(s) all three types, although in varying proportions. Traditionally, fibers were categorized depending on their varying color, which is a reflection of myoglobin content. Type I fibers appear red due to the high levels of myoglobin. Red muscle fibers tend to have more mitochondria and greater local capillary density. These fibers are more suited for endurance and are slow to fatigue because they use oxidative metabolism to generate ATP ( adenosine triphosphate ). Less oxidative Type II fibers are white due to relatively low myoglobin and
22275-414: The outer objects which it knows. Yet I must confess that for my part I cannot feel sure of this conclusion. [...] It seems as if consciousness as an inner activity were rather a postulate than a sensibly given fact... By the 1960s, for many philosophers and psychologists who talked about consciousness, the word no longer meant the 'inner world' but an indefinite, large category called awareness , as in
22440-465: The period of a person being awake, and they continue to transition into Stage 1 of sleep and in stage 2. Delta waves are seen in stages 3 and 4 of sleep when a person is in their deepest of sleep. Sleep is divided into two broad types: non-rapid eye movement (non-REM or NREM) sleep and rapid eye movement (REM) sleep. Non-REM and REM sleep are so different that physiologists identify them as distinct behavioral states. Non-REM sleep occurs first and after
22605-421: The phase of sleep and the type of memory. For example, declarative and procedural memory-recall tasks applied over early and late nocturnal sleep, as well as wakefulness controlled conditions, have been shown that declarative memory improves more during early sleep (dominated by SWS) while procedural memory during late sleep (dominated by REM sleep) does so. Consciousness Consciousness , at its simplest,
22770-403: The phenomenon of consciousness, because researchers lacked "a sufficiently well-specified use of the term...to agree that they are investigating the same thing". He argued additionally that "pre-existing theoretical commitments" to competing explanations of consciousness might be a source of bias. Within the "modern consciousness studies" community the technical phrase 'phenomenal consciousness'
22935-511: The process of somitogenesis the paraxial mesoderm is divided along the embryo 's length to form somites , corresponding to the segmentation of the body most obviously seen in the vertebral column . Each somite has three divisions, sclerotome (which forms vertebrae ), dermatome (which forms skin), and myotome (which forms muscle). The myotome is divided into two sections, the epimere and hypomere, which form epaxial and hypaxial muscles , respectively. The only epaxial muscles in humans are
23100-587: The properties of individual fibers—tend to be relevant and measured at the level of the motor unit, rather than individual fiber. Slow oxidative (type I) fibers contract relatively slowly and use aerobic respiration to produce ATP. Fast oxidative (type IIA) fibers have fast contractions and primarily use aerobic respiration, but because they may switch to anaerobic respiration (glycolysis), can fatigue more quickly than slow oxidative fibers. Fast glycolytic (type IIX) fibers have fast contractions and primarily use anaerobic glycolysis. The FG fibers fatigue more quickly than
23265-450: The proportion of REM sleep increases in the two cycles just before natural awakening. Awakening can mean the end of sleep, or simply a moment to survey the environment and readjust body position before falling back asleep. Sleepers typically awaken soon after the end of a REM phase or sometimes in the middle of REM. Internal circadian indicators , along with a successful reduction of homeostatic sleep need, typically bring about awakening and
23430-409: The quantum mechanical theories have been confirmed by experiment. Recent publications by G. Guerreshi, J. Cia, S. Popescu, and H. Briegel could falsify proposals such as those of Hameroff, which rely on quantum entanglement in protein. At the present time many scientists and philosophers consider the arguments for an important role of quantum phenomena to be unconvincing. Empirical evidence is against
23595-448: The range of descriptions, definitions or explanations are: ordered distinction between self and environment, simple wakefulness , one's sense of selfhood or soul explored by " looking within "; being a metaphorical " stream " of contents, or being a mental state , mental event , or mental process of the brain. The words "conscious" and "consciousness" in the English language date to
23760-411: The realm of consciousness and the realm of matter but give different answers for how the two realms relate to each other; and monist solutions that maintain that there is really only one realm of being, of which consciousness and matter are both aspects. Each of these categories itself contains numerous variants. The two main types of dualism are substance dualism (which holds that the mind is formed of
23925-430: The role of β-alanine as a neurotransmitter that promotes sleep in mice. Familial natural short sleep is a rare, genetic, typically inherited trait where an individual sleeps for fewer hours than average without suffering from daytime sleepiness or other consequences of sleep deprivation . This process is entirely natural in this kind of individual, and it is caused by certain genetic mutations. A person with this trait
24090-500: The rules for that language. Infants who slept within four hours of learning the language could remember the language rules better, while infants who stayed awake longer did not recall those rules as well. There is also a relationship between infants' vocabulary and sleeping: infants who sleep longer at night at 12 months have better vocabularies at 26 months. Children can greatly benefit from a structured bedtime routine. This can look differently among families, but will generally consist of
24255-454: The same fact, they are said to be Conscious of it one to another". There were also many occurrences in Latin writings of the phrase conscius sibi , which translates literally as "knowing with oneself", or in other words "sharing knowledge with oneself about something". This phrase has the figurative sense of "knowing that one knows", which is something like the modern English word "conscious", but it
24420-459: The same functional purpose. Within the zebrafish embryo, the Prdm1 gene down-regulates the formation of new slow twitch fibers through direct and indirect mechanisms such as Sox6 (indirect). In mice, the Prdm1 gene is present but does not control slow muscle genes in mice through Sox6 . In addition to having a genetic basis, the composition of muscle fiber types is flexible and can vary with
24585-399: The same muscle volume, increasing the physiological cross-sectional area (PCSA). This effect is known as fiber packing, and in terms of force generation, it more than overcomes the efficiency-loss of the off-axis orientation. The trade-off comes in overall speed of muscle shortening and in the total excursion. Overall muscle shortening speed is reduced compared to fiber shortening speed, as is
24750-663: The scent of rose, the taste of wine, or the pain of a headache. They are difficult to articulate or describe. The philosopher and scientist Daniel Dennett describes them as "the way things seem to us", while philosopher and cognitive scientist David Chalmers expanded on qualia as the " hard problem of consciousness " in the 1990s. When qualia is experienced, activity is simulated in the brain, and these processes are called neural correlates of consciousness (NCCs). Many scientific studies have been done to attempt to link particular brain regions with emotions or experiences. Species which experience qualia are said to have sentience , which
24915-469: The screens of electronic devices such as smartphones and televisions, which emit large amounts of blue light, a form of light typically associated with daytime. This disrupts the release of the hormone melatonin needed to regulate the sleep cycle . The most pronounced physiological changes in sleep occur in the brain. The brain uses significantly less energy during sleep than it does when awake, especially during non-REM sleep. In areas with reduced activity,
25080-524: The size principal of motor unit recruitment viable. The total number of skeletal muscle fibers has traditionally been thought not to change. It is believed there are no sex or age differences in fiber distribution; however, proportions of fiber types vary considerably from muscle to muscle and person to person. Among different species there is much variation in the proportions of muscle fiber types. Sedentary men and women (as well as young children) have 45% type II and 55% type I fibers. People at
25245-432: The skeletal muscle cell for the large amounts of proteins and enzymes needed to be produced for the cell's normal functioning. A single muscle fiber can contain from hundreds to thousands of nuclei. A muscle fiber for example in the human biceps with a length of 10 cm can have as many as 3,000 nuclei. Unlike in a non-muscle cell where the nucleus is centrally positioned, the myonucleus is elongated and located close to
25410-526: The specific fiber type. In zebrafish embryos, the first muscle fibers to form are the slow twitch fibers. These cells will undergo migration from their original location to form a monolayer of slow twitch muscle fibers. These muscle fibers undergo further differentiation as the embryo matures. In larger animals, different muscle groups will increasingly require different fiber type proportions within muscle for different purposes. Turtles , such as Trachemys scripta elegans , have complementary muscles within
25575-444: The specific nature of the connection is unknown. The first influential philosopher to discuss this question specifically was Descartes , and the answer he gave is known as mind–body dualism . Descartes proposed that consciousness resides within an immaterial domain he called res cogitans (the realm of thought), in contrast to the domain of material things, which he called res extensa (the realm of extension). He suggested that
25740-411: The suprachiasmatic nucleus has a direct neural connection to the pineal gland , which releases the hormone melatonin at night. Cortisol levels typically rise throughout the night, peak in the awakening hours , and diminish during the day. Circadian prolactin secretion begins in the late afternoon, especially in women, and is subsequently augmented by sleep-induced secretion, to peak in the middle of
25905-423: The total distance of shortening. All of these effects scale with pennation angle; greater angles lead to greater force due to increased fiber packing and PCSA, but with greater losses in shortening speed and excursion. Types of pennate muscle are unipennate , bipennate , and multipennate . A unipennate muscle has similarly angled fibers that are on one side of a tendon. A bipennate muscle has fibers on two sides of
26070-407: The traditional idea of the phenomenon called 'consciousness', writing that "its denotative definition is, as it was for Descartes , Locke , and Hume , what is introspectable". Jaynes saw consciousness as an important but small part of human mentality, and he asserted: "there can be no progress in the science of consciousness until ... what is introspectable [is] sharply distinguished" from
26235-406: The transmission of force from muscle contraction to the skeletal system. Muscle architecture refers to the arrangement of muscle fibers relative to the axis of force generation , which runs from a muscle's origin to its insertion . The usual arrangements are types of parallel , and types of pennate muscle . In parallel muscles, the fascicles run parallel to the axis of force generation, but
26400-419: The trough of the cycle. A healthy young adult entrained to the sun will (during most of the year) fall asleep a few hours after sunset, experience body temperature minimum at 6 a.m., and wake up a few hours after sunrise. Generally speaking, the longer an organism is awake, the more it feels a need to sleep ("sleep debt"). This driver of sleep is referred to as Process S . The balance between sleeping and waking
26565-449: The various methods are mechanistically linked, while others are correlated in vivo . For instance, ATPase fiber type is related to contraction speed, because high ATPase activity allows faster crossbridge cycling . While ATPase activity is only one component of contraction speed, Type I fibers are "slow", in part, because they have low speeds of ATPase activity in comparison to Type II fibers. However, measuring contraction speed
26730-440: The world of introspection , of private thought , imagination , and volition . Today, it often includes any kind of cognition , experience , feeling , or perception . It may be awareness, awareness of awareness, metacognition , or self-awareness , either continuously changing or not. The disparate range of research, notions and speculations raises a curiosity about whether the right questions are being asked. Examples of
26895-488: The world, but of entities, or identities, acting in the world. Thus, by speaking of "consciousness" we end up leading ourselves by thinking that there is any sort of thing as consciousness separated from behavioral and linguistic understandings. Ned Block argued that discussions on consciousness often failed to properly distinguish phenomenal (P-consciousness) from access (A-consciousness), though these terms had been used before Block. P-consciousness, according to Block,
27060-440: Was but a small part of mental life", and this idea underlies the goal of Freudian therapy , to expose the unconscious layer of the mind. Other metaphors from various sciences inspired other analyses of the mind, for example: Johann Friedrich Herbart described ideas as being attracted and repulsed like magnets; John Stuart Mill developed the idea of "mental chemistry" and "mental compounds", and Edward B. Titchener sought
27225-533: Was rendered into 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". The Latin conscientia , literally 'knowledge-with', first appears in Roman juridical texts by writers such as Cicero . It means a kind of shared knowledge with moral value, specifically what a witness knows of someone else's deeds. Although René Descartes (1596–1650), writing in Latin,
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