Physiology Of Sleep

Physiology Of Sleep Physiology Of Sleep Introduction Sleep is a state of reversible unconsciousness in which the brain is low responsive to external stimuli. We are functionally blind during sleep with no response to visual stimuli and a decreased threshold of response to auditory stimuli. Babies have been exposed to sound of up to 100 dB, which is above the legal limit for ear protection for employees, without waking up. In adults, the action is selective demonstrating continuing cortical function. For example, a sleeping mother is woken by her crying baby but not by other louder noises. Definition of sleep and sleeping Phases with specific EEG patterns and physiological changes. Natural sleep is separated into two distinctive states: non rapid eye movement (N.R.E.M) and rapid eye movement (REM) sleep. NREM sleep is then further seperated into 4 stages where stage 1 is the lightest and stage 4 the deepest level of sleep. REM sleep is divided into phasic and tonic phases. The two distinctive states follow a regular pattern called a sleep cycle which, in an adult, lasts about 1 and half hours and comprises a period of N.R.E.M sleep followed by REM sleep. The cycles may be separated by a period of wakefulness and are repeated 3–6 times each night and are typically displayed as an hypnogram (Fig. 1). The majority of deep (stage 4) NREM sleep occurs in the first and second cycles. As the night progresses, the proportion of REM sleep in a cycle increases and the NREM element is of lighter stage 2 sleep. Age has a major effect on the duration of sleep and the ratio of NREM/REM sleep. Neonates sleep 16–18 h. It is widely distributed throughout the day with REM sleep accounting for 50% of total sleep time (TST). This may be even greater in premature babies. By the age of 24 months, children should sleep 10 h per day, mainly at night with one or two naps during the daytime and REM sleep has declined to 20–25% of TST. Adults normally sleep 6–8 h per day with 15–20% REM sleep. With increasing age, TST changes little although sleep is more fragmented with more frequent and longer awakenings (decreased sleep efficiency) with less REM sleep and more light NREM sleep. Night-time sleep may be decreased if naps are taken during the day. Functions of sleep The functions of sleep are still poorly understood. However, the observation that sleep (or, at  least, an activity–inactivity cycle) is present in all species and has been preserved throughout evolution and that sleep deprivation leads to a drastic deterioration in cognitive  function and eventually to mental and physical morbidity proves its importance. It has been suggested that sleep might conserve energy by reducing core temperature slightly and lowering metabolic rate by 10% compared with quiet wakefulness. Sleep would prevent perpetual activity as a response to environmental stimuli leading to excessive energy consumption. However, sleep is a state of starvation and there is no evidence that sleep is important for tissue repair. Sleep has been implicated as an important factor in storage of long-term memory. Facts learned during the day are usually better remembered the next morning whereas facts learned shortly before going to sleep are often poorly recalled. Electrophysiological features of sleep The stages of sleep are characterised by typical patterns of electroencephalogram (EEG), electro-myogram (EMG) and electro oculogram (EOG) activity Wakefulness with open eyes is characterised by an EEG with dominant low amplitude, high frequency beta activity of  16–25 Hz. Muscle tone is normally high with high to moderate EMG activity. Stage 1 Sleep is usually initiated by a transition from wakefulness to a state of drowsiness with closed eyes and a shift from EEG beta activity to alpha activity of 8–12 Hz passing to Stage 1  NREM sleep with a mixed frequency EEG-pattern with low amplitude theta waves of 3–7 Hz accompanied by slow rolling eye movements. Involuntary muscle clonus occurs frequently,  resulting in jerky movement of the whole body (hypnic jerks) and EMG activity is moderate-to-low. This stage lasts typically only 5–10 min, during which time minor auditory stimuli will cause arousal. Stage 2 Stage 2 is characterised by short bursts of high frequency activity (12–15 Hz – sleep spindles) and K-complexes (large amplitude biphasic waves). Bodily movements continue and  the EMG activity is low-to-moderate. This stage is generally short (10–20 min) in the first 1–2 cycles but predominates in later cycles. It is the most abundant sleep stage in adults  accounting for up to 50% of TST. Stages 3 and 4 Deep NREM sleep stages 3 and 4, sometimes combined as slow wave sleep (SWS) are characterized by high amplitude low frequency delta waves (> 75 µV and 0.5–2 Hz) with stage  3 having between 20–50% and stage 4 more than 50% delta activity. EMG activity is low and eye movements are rare. Arousal through auditory stimuli from this stage of sleep is  difficult and, if awakened, the individual is often disorientated and slow to react. Return to sleep is easy and short arousals (< 30 sec) are rarely remembered. REM sleep NREM sleep is followed by REM sleep, the proportion increasing with each cycle. REM sleep is characterised by a fast mixed frequency low voltage EEG with saw-tooth waves and  rapid eye movements on the EOG. During the tonic phases of REM sleep, there is marked reduction of muscle tone and EMGactivity in skeletal muscles. The tonic phases of REM sleep are interrupted by short episodes of phasic REM sleep with increased EMG activity and limb twitches. The atonia of REM sleep affects all skeletal muscles, except the diaphragm and the upper airway muscles, and is associated with hyperpolarisation of the ÃŽ ±-motor neurones. The purpose of this may be to prevent the acting out of dreams. About 10% of the population have experienced sleep paralysis (i.e. wakening from sleep and finding that the atonia has  persisted into wakefulness). It can be frightening but is entirely harmless. Natural wakening usually occurs from REM sleep. Subjects woken from REM sleep are much more likely to rec all dream content than those awakened from NREM sleep. NREM dreams are generally vague and formless in contrast to REM dreams. Physiological changes during sleep Respiratory system During NREM sleep, there is a decrease in respiratory drive and a reduction in the muscle tone of the upper airway leading to a 25% decrease in minute volume and alveolar ventilation and a doubling of airway resistance accompanied by a small (0.5 kPa) increase in  PaCO2 and decrease in PaO2. Hypercarbic and hypoxic ventilator drives are reduced compared with wakefulness. The breathing pattern is regular except at the transition from wakefulness into sleep when brief central apnoeas are common. During REM sleep there is a further decrease in hypercarbic and, particularly, hypoxic ventilatory drives. The breathing pattern is irregular especially during phasic REM sleep. The loss of skeletal muscle tone in REM sleep affects the intercostal and other muscles which stabilise the chest wall during inspiration. In infants, this may be seen as paradoxical movement of the rib cage and abdomen. In adults, there may be maldistribution of ventilation and impaired ventilation–perfusion matching with consequent arterial hypoxaemia. In normal subjects, this is unimportant but it may be very important in patients with chronic lung disease or abnormalities of the thoracic (e.g. kyphoscoliosis). The great majority of patients with impaired respiratory function will be at their worst during REM sleep. Cardiovascular system Blood pressure decreases during NREM and tonic REM sleep but may increase above waking values during phasic REM sleep. Cardiac output is generally decreased during all sleep  phases. Systemic vascular resistance (SVR) and the heart rate are both reduced during NREM and tonic REM sleep and increased during phasic REM sleep. Central nervous system Cerebral blood flow (CBF) increases by 50–100% above the level of resting wakefulness during tonic REM sleep and is even greater during phasic REM sleep. Cerebral metabolic rate, oxygen consumption and neuronal discharge rate are reduced during NREM sleep but increased above resting values during REM sleep. The autonomic nervous system shows a general decrease in sympathetic tone and an increase in parasympathetic tone,  except in phasic REM sleep. Renal system The glomerular filtration speed and filtration fraction are reduced and ADH secretion is increased resulting in a less volume concentrated urine. Endocrine system The secretion of several hormones is directly linked to the sleep/wake cycle. Melatonin is released from the pineal gland under the control of the supra-chiasmatic nuclei (SCN) in a 4–5h pulse, usually beginning at the onset of darkness (~9 pm). The pulse is inhibited or delayed by exposure to bright light in the evening. It is best regarded as being permissive of sleep (‘opening the gate to sleep’) rather than as an hypnotic, as it is possible to maintain wakefulness during this period. Growth hormone is mostly secreted during the first episode of SWS, particularly  during puberty. Prolactin concentrations also increase shortly after sleep onset and decrease with wakefulness. Sleep phase delay delays secretion of both of these hormones. The secretion of cortisol decreases with the onset of sleep and reaches a trough in the early hours of the morning and a peak just after waking. Temperature control In contrast to anaesthesia, thermoregulation is maintained during sleep. However, the shivering threshold is decreased and body core temperature decreases by about 0.5 °C in humans and 2 °C  in hibernating mammals. Body temperature is linked to the circadian rhythm and reaches its nadir at about 3 am. Thermoregulation is quite good in human infants compared with  other species. Control of sleep Sleep follows a circadian (~1 day) cycle, the periodicity of which is regulated by an independent genetically determined ‘intrinsic clock’ which is entrained to a 24 h cycle by external cues (Zeitgebers) such as light, darkness, clock time, working patterns and meal times. When a human being is deprived of all external time clues and is exposed to constant levels of illumination (‘free running’), the wake/sleep cycle typically lengthens to about 24.5 h. Subjects who are born blind without any appreciation of light generally free run while those blinded in later lifeor who retain some perception of light remain entrained. All living organisms, including plants and fungi, have been found to have clock genes and to show an inactivity/activity cycle. In mammals, control of the intrinsic clock is located in the SCN on either side of the third ventricle, just above the optical chiasm. In animal experiments, its destruction leads to a change from the normal sleep cycle into several shorter sleep/activity periods during the day. As noted above, melatonin secretion is  prompted by the SCN just before the usual time of sleep onset. A mismatch of this pattern with sleeping time, as occurs in shift workers and after trans-meridian flights, leads to sleep disturbance (‘jet lag’) as the subject is trying to sleep during their circadian day. Light therapy can be helpful in re-setting the circadian clock and the interested reader is referred to the bibliography. The propensity to fall asleep varies throughout the day and depends upon both circadian factors (process C) and time since the last sleep period (process S). The longer the time since the  last sleep period, the greater will be process S. However, its propensity will be modulated by process C. The circadian pressure to sleep is greatest at ~2 am with a secondary peak at ~2 pm. It is least at ~6 am and ~6 pm. If a subject elects to stay awake throughout the night, they will feel most sleepy in the small hours of the morning but will get a ‘second wind’ as morning approaches and the circadian pressure to sleep declines. If wakefulness is maintained, a second period of sleepiness and relative alertness will follow in early afternoon and early evening, respectively. Some of the 8-h sleep debt will be recovered that night but process C will ensure that awakening will occur at or shortly after the normal waking time. Sleep is normally an actively initiated and not a passive process. Unless a subject is sleep deprived, successful initiation of sleep depends both upon the phase of the circadian clock and  external factors (recumbent position, darkness, reducing sensory input). Over the years, considerable effort has been focused on a search for: (i) a ‘sleep centre’, a nucleus or region in the brain where stimulation or ablation would lead to sleep; and (ii) a hormone or transmitter which would reliably induce sleep. Neither have been found because the mechanisms resulting in sleep are complex and diffuse. During wakefulness, the CNS is dominated by activity of the ascending reticular activating system (RAS) in the brain stem. This formation receives sensory input from all peripheral sensors and projects to the thalamus and the cortex. Its main neurotransmitters are acetylcholine, noradrenaline, dopamine and histamine which explains the sedative effect of antagonists to these  substances. A decrease in its activity permits sleep to be initiated by suppressing incoming external stimuli. The induction of SWS is associated with the secretion of ÃŽ ³-aminobutyric acid (GABA) from basal forebrain neurones. Therefore, it is not surprising that benzodiazepines and barbiturates, which act through stimulation of GABA receptors in the CNS, induce sleep or anaesthesia. Cholinergic mechanisms initiate REM sleep through stimulation of pontine neurones in the  lateral portion of the pontine tegmentum and the nucleus reticularis pontis oralis. In animal experiments, injection of carbachol (acetylcholine agonist) induces instantaneous REM sleep. Recently, orexins (hypocretin) have been isolated in the hypothalamus and appear to be important in the control of REM sleep and appetite. CSF concentrations of orexins have been found to be very low in patients with narcolepsy. Influence of surgery and anaesthesia on sleep Anaesthesia and surgery can have a profound effect upon sleep. On the first night after surgery, sleep architecture is severely disrupted with little or no SWS and REM sleep. The  light Stage 2 sleep is fragmented with frequent awakenings. The degree of disruption appears to be related to the severity of the surgical insult. The mechanism is unclear but it is probably due to a combination of the surgical stress and the effects of opioid analgesics. Recovery of lost SWS and REM sleep occurs on postoperative nights 2–5, being later after major surgery. This coincides with the nadir of postoperative pulmonary function and several  studies have demonstrated marked hypoxaemia associated with the rebound of REM sleep. It was a logical step to attribute postoperative myocardial ischaemia, myocardial infarction, pulmonary embolism and cerebral disorder (delirium and cognitive impairment) to nocturnal hypoxaemia. However, a number of studies have failed to confirm these presumed associations,  although this does not exclude the possibility that the hypoxaemia may be important in some individuals. Key references Ambrosini MV, Giuditta B. Learning and sleep: the sequential hypothesis. Sleep Med Rev2001;5: 477–90 Dijk DJ, Lockley SW. Functional genomics of sleep and circadian rhythm: integration of human sleep-wake regulation and circadian rhythmicity.J Appl Physiol 2002;92: 852–62 Douglas N.Clinician’s Guide to Sleep Medicine. Edinburgh:Arnold, 2002   Ebrahim IO et al. The hypocretin/orexin system. J R Soc Med 2002;95: 227–30 Kryger MH, Roth T, Dement WC. (eds) Principles and Practice of Sleep Medicine, 3rd edn. Philadelphia: 2000. Nicolau MC et al.Why we sleep: the evolutionary pathway to the mammalian sleep pattern.Prog Neurobiol2000;62: 379–406 Saper CB, Chou TC, Scammell TE.The sleep switch: hypothalamic control of sleep and wakefulness.Trends Neurosci2001;24: 726–31 Shneerson JM.Handbook of Sleep Medicine. Oxford: Blackwell, 2000 Williams JM, Hanning CD. Obstructive sleep apnoea,BJA CEPD Rev2003; 3: 75–78

Looking for a hotel where kids are welcome? :: Essays Papers

Looking for a hotel where kids are welcome? GRAPH The well-known comic The Family Circus by Bil Keane, which is run in over 1500 newspapers, shows the hectic life of an American family, giving meaning to the saying, "Kids will be kids." It is based on the actual life of Bil Keane’s family and his experiences as a child. The most commonly noted features of his comic are the circular shape he often encloses the pictures in, and the dotted line that follows the children around, giving away their every move. Many other cartoonists try to capture the Family Circus mood by incorporating these features into their own works. GRAPH The Wyndham Hotels & Resorts advertisement uses this technique to show the path your child may take around the room of a hotel, where there is nothing else for them to do. It describes the creative and active characteristics of children, who require near constant entertainment that keeps them busy and uses their developing mind. At Wyndham hotels, they understand that keeping your children entertained is a challenging task for you, the parent, which is why they provide an activity package for your kids. The disapproving glare from behind the desk that is sometimes given to parents as they walk into a nice hotel with their three young children is often mirrored to pet-owners, which I can relate to. This gives you a feeling of insecurity and makes you feel unwelcome. I know I appreciate when the hotel at which I am planning to stay has a special feature for pets because then I know not only am I welcome, but that they also welcome my dog. The feeling is similar with parents wanting their children to be welcome. You know from watching Nickelodeon and Nick Jr. with your kids, how much they love Spongebob Squarepants. Moreover, you know that sleepovers are fun. Wyndham Hotels & Resorts also know this, which is why they are advertising this Spongebob Squarepants sleepover party package.

Benifits of Academic Globalization Essay

2. Introduction: Globalization is one of the most discussed issues nowadays. It has several branches which vary from economic, cultural, academic, and industrial and many more. However, the one that is increasing at a very high rate is academic globalization. Since academic globalization includes the act of studying abroad, it can be defined as is the act of traveling of students to study in a country other than the mother one. Nowadays, students are getting many Academic Globalization l 3 opportunities to study abroad, in addition to other reasons, which is why they are studying outside their home countries. â€Å"He [Wiladavsky] stated that 3 million students are now studying outside their home countries, a 57% increase from 2000† (Apurvadesai, 2010, p. 1). These numbers show the tremendous increase in movement of students around the world. Academic globalization has become one of the most debatable issues. People who are against it believe that once the students graduate and see many opportunities to work abroad they would not come back. On the other hand, people who are with it believe that it provides the students with better education and higher experience. In fact, academic globalization can be beneficial in several ways. 3. Literature review: Apurvadesia (2010), comments on the discussion of the World Affairs council which focuses on the rise of academic globalization. According to Wiladavsky, who was among the speakers, there is an increase in the movement of students around the world. Moreover, he discussed the concept of global ranking that motivates students to work and study harder to reach their goals and become part of the top class. In addition to that, Apurvadesia states that the idea of brain drain is actually brain circulation. Wiladavsky (2010), argues that countries should not be afraid from globalization. On the contrary, Wiladavsky tries to shed the light on the benefits of academic globalization. He believes that it helps in expanding knowledge and in trading of minds. Moreover, Wiladavsky tries to shed the light on the opposing point of view and give reasons behind the fear of globalization. Academic Globalization l 4 Wiladavsky (2010), focuses on why colleges should support globalization. Wiladavsky argues by believing that globalization of higher education helps in identifying talents. Moreover, he believes that successful competition is achieved by higher education. Goodman(2013), argues that Americans should study abroad in order to get  international experience. Moreover, he believes that student would appreciate difference and diversity through meeting new people. In addition to that, he considers that by interacting with people from different countries, students would be trained to all sectors of leaders. 4. Better education: One of the main reasons why academic globalization is beneficial is by offering a better education for the students. This is due to the fact that more opportunities and better experience are provided. 4. 1 More opportunities: Students get better education by having a wide variety of majors to choose where they fit. Some countries lack majors which are  available in others and thus, instead of doing a major that they are not interested in, they have the opportunity to study abroad the major they always dreamt of. For example, in Lebanon, petroleum engineering is not available; however, some students are interested in such a major. So instead of looking for another major to study, they can simply apply in another country which includes such majors. Moreover, a master degree is another opportunity provided in some countries and deprived in others. In developed countries such as USA or Europe, the master degree offered provides the students with better credentials. Students  Academic Globalization l 5 would be more knowledgeable and updated to recent discoveries. A student having a BS degree has less opportunity than a student having a master degree when applying a certain job especially, if the master degree was from a country offering a higher education. 4. 2 More experience: Another reason why students are provided with a better education is the high experience they get. The concept of brain circulation applies here, where students get different degrees from different countries. † A student may leave China, go to Singapore for an undergraduate degree, then to US for a Master’s degree, then  Australia to work for a couple of years, then back to China for a job with a multi-national company†(Apurvadesai, 2010,p. 2). In this example, Apurvadesai describes how having the opportunity to study in different countries provides the student with the higher experience and characteristics required for a job in a multi-national company. Moreover, living in a different country, having different culture, language, habits and lifestyle, increase experience. When students travel, they try to accommodate with the changes around them. This process provides them with higher experience when it comes to dealing with other countries. In addition to that, students will be provided with better communication skills. They would learn to speak new languages fluently due to practice and would be familiar with the demand of other countries. In this way, if there was a foreign customer, Academic Globalization l 6 the student will directly provide him/her with the service he/she is more likely to be interested in. 5. Expands global knowledge: Another reason why academic globalization is beneficial is that it helps in expanding knowledge across the world. This is achieved by discovering new talents. Some countries are deprived from a variety of domains. On the contrary,  when students travel to encounter their education, they would be exposed to a wide selection of domains. In this way, students would be able to discover new talents in them and introduce it to their local country. Moreover, academic globalization promotes the sharing of information between countries. When students get their education in a foreign country, they would be introduced to new concepts, studies and researches. People against academic globalization argue that the country offering the higher education takes away from the learning of the native country. However, introducing new concepts is not bad to other countries. In fact, as RAND economist James Hosek told the Cronicle of Higher Education that â€Å"When new knowledge is created, it is a public good and can be used by many†(Wiladavsky, 2010, p. 3). When students return back to their countries, they would share the knowledge they acquired and help in developing their nations. 6. Conclusion: In conclusion, academic globalization is a trend that is increasing at a very high rate. It is a one of the most debatable issues in the society. Some people are with it and think it is beneficial, while others are against it and think it is harmful. However, it can be beneficial in several ways. It provides better education for Academic Globalization l 7 students through having more experiences and opportunities. Moreover, academic globalization promotes global knowledge between different countries leading to the free trade of mind. In fact, people should support academic globalization to develop the whole world. 7. References: Apurvadesai. (May 15, 2010). Academic Globalization- The Emergence of International Universities. In Reading, Writing and Reflecting. Retrieved from http://apurvadesai. com/2010/05/15/academic-globalization-the-emergence -of-international-universities/ Goodman, A. E. , Berdan, S. N. (October 17, 2013). A Year Abroad vs. a Year Wasted. In The New York Times. Retrieved from, http://www. nytimes. com/roomfordebate/2013/10/17/should-more-american s-study-abroad/every-student-should-study-abroad Wildavsky, B. (January 5, 2010). Academic Globalization Should Be Welcomed. Not Feared. In Brookings. Retrieved from, http://brookings. edu/research/articles/2010/01/15- globalization-wildavsky. Wildavsky, B. (April 4, 2010). Why Colleges Shouldn’t Fear Global Competition. In The Chronicle of Higher Education. Retrieved from, http://chronicle. com/article/The-Global-Benefits-of/64932/. Academic Globalization l 8

Queen Of Katwe A Reflection And Comparison - 1003 Words

Queen of Katwe: A Reflection and Comparison Poverty. Sickness. Poor education. The people in the movie Queen of Katwe live a hard life, yet they are still happy and hard working. This movie has many important morals in it, but the one most important to the story line would be about overcoming obstacles. â€Å"In chess, the small one can become the big one. That’s why I like it.† This quote is about chess, but it applies to our lives too. Growing up is all about overcoming obstacles, and the characters in the movie faced many difficulties. Phiona, for example, overcomes the obstacle of the children s taunts when she first goes to a chess meeting. She goes back again and again and perseveres to get the practice she needs, and eventually becomes†¦show more content†¦Another similarity would be that the children really value the opportunities available to them. I really appreciate the christian school and the sports that are an option for me, because those things aren’t accessible to everyone, just l ike how Phiona and the other kids all value the game of chess and any education they can get. Even in vastly different situations there are always ways people can relate to one another and show their worldviews. The elements of worldview all bring up differences between the worldviews and ways of life in Uganda compared to here in Canada. Geography, time, knowledge, economy, society, and beliefs and values; Each of them are important in shaping our perspectives. The danger at night, hair cut short to avoid disease, and terrible floods are examples of geographical things that could make Phiona’s worldview different from mine. An important display of time throughout the movie is Phiona’s happiness. Near the beginning of the movie, a neighbor asks how her life is going, and she replies that it is fine. But after losing one of her tournaments she comes home and lays in bed, depressed. She does not respond when asked again how she is. After introducing the game of chess to her worldview, Phiona finds she is unhappy when she does not play it anymore. Eventually she plays again, and when she wins the championship, she is overjoyed. â€Å"Losses happen to everyone. But then we reset the pieces and