examples of positive feedback in the human body

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From Wikipedia

Feedback

Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or occurrences of the same (i.e. same defined) event / phenomenon (or the continuation / development of the original phenomenon) in the present or future. When an event is part of a chain of cause-and-effect that forms a circuit or loop, then the event is said to "feed back" into itself.

Feedback is also a synonym for:

  • Feedback signal - the information about the initial event that is the basis for subsequent modification of the event
  • Feedback loop - the causal path that leads from the initial generation of the feedback signal to the subsequent modification of the event
  • Audio feedback- the special kind ofpositive feedback that occurs when a loop exists between an audio input and output.

Overview

Feedback is a mechanism, process or signal that is looped back to control a system within itself. Such a loop is called a feedback loop. In systems containing an input and output, feeding back part of the output so as to increase the input is positive feedback (regeneration); feeding back part of the output in such a way as to partially oppose the input is negative feedback (degeneration).

In more general terms, a control system has input from an external signal source and output to an external load; this defines a natural sense (or direction) or path of propagation of signal; the feedforward sense or path describes the signal propagation from input to output; feedback describes signal propagation in the reverse sense. When a sample of the output of the system is fed back, in the reverse sense, by a distinct feedback path into the interior of the system, to contribute to the input of one of its internal feedforward components, especially an active device or a substance that is consumed in an irreversible reaction, it is called the "feedback". The propagation of the signal around the feedback loop takes a finite time because it is causal.

The natural sense of feedforward is defined chemically by some irreversible reaction, or electronically by an active circuit element that has access to an auxiliary power supply, so as to be able to provide power gain to amplify the signal as it propagates from input to output. For example, an amplifier can use power from its controlled power reservoir, such as its battery, to provide power gain to amplify the signal; but the reverse is not possible: the signal cannot provide power to re-charge the battery of the amplifier.

Feedforward, feedback and regulation are self related. The feedforward carries the signal from source to load.

Negative feedback helps to maintain stability in a system in spite of external changes. It is related to homeostasis. For example, in a population of foxes (predators) and rabbits (prey), an increase in the number of foxes will cause a reduction in the number of rabbits; the smaller rabbit population will sustain fewer foxes, and the fox population will fall back. In an electronic amplifier feeding back a negative copy of the output to the input will tend to cancel distortion, making the output a more accurate replica of the input signal

Positive feedback amplifies possibilities of divergences (evolution, change of goals); it is the condition to change, evolution, growth; it gives the system the ability to access new points of equilibrium.

For example, in an organism, most positive feedback provides for fast autoexcitation of elements of endocrine and nervous systems (in particular, in stress responses conditions) and are believed to play a key role in morphogenesis, growth, and development of organs, all processes that are, in essence, a rapid escape from the initial state. Homeostasis is especially visible in the nervous and endocrine systems when considered at organism level. Chemical potential energy for irreversible reactions or electrical potential energy for irreversible cell-membrane current powers the feedforward sense of the process. However, in the case of morphogenesis, feedback may only be enough to explain the increase in momentum of the system, and may not be sufficient in itself to account for the movement or direction of its parts.

When a public-address system is used with a microphone to amplify speech, the output from a random sound at the microphone may produce sound at a loudspeaker that reaches the microphone such as to reinforce and amplify the original signal (positive feedback), building up to a howl (of frequency dependent upon the acoustics of the hall). A similar process is used deliberately to produce oscillating electrical signals.

Feedback is distinctly different from reinforcement that occurs in learning, or in conditioned reflexes. Feedback combines immediately with the immediate input signal to drive the responsive power gain element, without changing the basic responsiveness of the system to future signals. Reinforcement changes the basic responsiveness of the system to future signals, without combining with the immediate input signal. Reinforcement is a permanent change in the responsiveness of the system to all future signals. Feedback is only transient, being limited by the duration of the immediate signal.

Types of feedback

When feedback acts in response to an event/phenomenon, it can influence the input signal in one of two ways:

  1. An in-phase feedback signal, where a positive-going wave on the input leads to a positive-going change on the output, will amplify the input signal, leading to more modification. This is known as positive feedback.
  2. A feedback signal which is inverted, where a positive-going change on the input leads to a negative-going change on the output, will dampen the effect of the input signal, leading to less modification. This is known as negative feedback.
  • Note that an increase or decrease of the feedback signal here refers to themagnitude relative to the input signal's absolute value, without regard to the polarity or sign of the feedback signal. For example if the input signal changes by 100 then a change in feedback signal value from +5 to +10 is a positive feedback. If the input signal changes by -100 then a change in the feedback signal from -5 to -10 is also a positive feedback.

Positive feedback tends to increase the

360-degree feedback

In human resources or industrial/organizational psychology, 360-degree feedback, also known as multi-rater feedback,multisource feedback, or multisource assessment, is feedback that comes from all around an employee. "360" refers to the 360 degrees in a circle, with an individual figuratively in the center of the circle. Feedback is provided by subordinates, peers, and supervisors. It also includes a self-assessment and, in some cases, feedback from external sources such as customers and suppliers or other interested stakeholders. It may be contrasted with "upward feedback," where managers are given feedback by their direct reports, or a "traditional performance appraisal," where the employees are most often reviewed only by their managers.

The results from 360-degree feedback are often used by the person receiving the feedback to plan training and development. Results are also used by some organizations in making administrative decisions, such as pay or promotion. When this is the case, the 360 assessment is for evaluation purposes, and is sometimes called a "360-degree review." However, there is a great deal of controversy as to whether 360-degree feedback should be used exclusively for development purposes, or should be used for appraisal purposes as well (Waldman et al., 1998). There is also controversy regarding whether 360-degree feedback improves employee performance, and it has even been suggested that it may decrease shareholder value (Pfau & Kay, 2002).

History

The German Military first began gathering feedback from multiple sources in order to evaluate performance during World War II (Fleenor & Prince, 1997). Also during this time period, others explored the use of multi-rater feedback via the concept of T-groups.

One of the earliest recorded uses of surveys to gather information about employees occurred in the 1950s at Esso Research and Engineering Company (Bracken, Dalton, Jako, McCauley, & Pollman, 1997). From there, the idea of 360-degree feedback gained momentum, and by the 1990s most human resources and organization development professionals understood the concept. The problem was that collecting and collating the feedback demanded a paper-based effort including either complex manual calculations or lengthy delays. The first led to despair on the part of practitioners; the second to a gradual erosion of commitment by recipients.

Multi-rater feedback use steadily increased in popularity, due largely to the use of the Internet in conducting web-based surveys (Atkins & Wood, 2002). Today, studies suggest that over one-third of U.S. companies use some type of multi-source feedback (Bracken, Timmereck, & Church, 2001a). Others claim that this estimate is closer to 90% of all Fortune 500 firms (Edwards & Ewen, 1996). In recent years, Internet-based services have become the norm, with a growing menu of useful features (e.g., multi languages, comparative reporting, and aggregate reporting) (Bracken, Summers, & Fleenor, 1998).

Accuracy

A study on the patterns of rater accuracy shows that length of time that a rater has known the person being rated has the most significant effect on the accuracy of a 360-degree review. The study shows that subjects in the group “known for one to three years� are the most accurate, followed by “known for less than one year,� followed by “known for three to five years� and the least accurate being “known for more than five years.� The study concludes that the most accurate ratings come from knowing the person long enough to get past first impressions, but not so long as to begin to generalize favorably (Eichinger, 2004).

It has been suggested that multi-rater assessments often generate conflicting opinions, and that there may be no way to determine whose feedback is accurate (Vinson, 1996). Studies have also indicated that self-ratings are generally significantly higher than the ratings of others (Lublin, 1994; Yammarino & Atwater, 1993; Nowack, 1992).

Results

Several studies (Hazucha et al., 1993; London & Wohlers, 1991; Walker & Smither, 1999) indicate that the use of 360-degree feedback helps people improve performance. In a 5-year Walker and Smither (1999) study, no improvement in overall ratings was found between the 1st and 2nd year, but higher scores were noted between 2nd and 3rd and 3rd and 4th years. A study by Reilly et al. (1996) found that performance increased between the 1st and 2nd administrations, and sustained this improvement 2 years later. Additional studies show that 360 feedback may be predictive of future performance (Maylett & Riboldi, 2007).

Some authors maintain that 360 processes are much too complex to make blanket generalizations about their effectiveness (Bracken, Timmreck, Fleenor, & Summers, 2001b; Smither, London, & Reilly, 2005). Smither et al. (2005) suggest, "We therefore think that it is time for researchers and practitioners to ask, 'Under what conditions and for whom is multisource feedback likely to be beneficial?' (rather than asking 'Does multisource feedback work?') (p. 60)." Their meta-analysis of 24 longitudinal studies looks at individual and organizational moderators that point to many potential determinants of behavior change, including positive feedback orientation, positive reactions to feedback, goal setting, and taking action.

Bracken et al. (2001b) and Bracken and Timmreck (2001) focus on process features that are likely to also have major effects in creating behavior change and offer best practices in those areas. Some of these factors have been researched and been shown to have significant impact. Greguras and Robie (1998) document how the number of raters used in each rater category (direct report, peer, manager) affects the reliability of the feedback, with direct reports being the least reliable and therefore requiring more participation. Multiple pieces of research (Bracken & Paul, 1993; Kaiser & Kaplan, 2006; Caputo & Roch, 2009; English, Rose, & McClellan, 2009) have demonstrated that the response scale can have a major effect on the results, and some response scales are indeed better than others. Goldsmith and Underhill (2001) report the powerful influence of the participant behavior of following up with raters to discuss their results. Other potentially powerful moderators of behavior change include how raters are selected, manager approval, instrument quality (reliability and validity), rater training and orientation, participant training, manager (supervisor) training, coaching, integration with HR systems, and accountability (Bracken et al., 2001b).

Others indicate that the use of multi-rater assessment may not improve company performance. A 2001 Watson Wyatt study found that 360-degree feedback was associated with a 10.6 percent decrease in market value. Others claim that "there is no data showing that [360-degree feedback] actually improves productivity, increases retention, decreases grievances, or is superior to forced ranking and standard performance appraisal systems. It sounds good, but there is no proof it works." (Pfau & Kay, 2002) Similarly, Seifert, Yukl, and McDonald (2003) state that there is little evidence that the multi-rater process results in change.

Additional studies (Maylett, 2005) found no correlation between an

Humanities

The humanities are academic disciplines which study the human condition, using methods that are primarily analytical, critical, or speculative, as distinguished from the mainly empirical approaches of the natural science.

Examples of the disciplines of the humanities are ancient and modern languages, literature, law, history, philosophy, religion, and visual and performing arts (including music and theatre). Additional subjects sometimes included in the humanities are technology, anthropology, area studies, communication studies, cultural studies, and linguistics, although these are also regarded as social sciences. Scholars working in the humanities are sometimes described as "humanists". However, that term also describes the philosophical position of humanism, which some "antihumanist" scholars in the humanities reject.

Humanities fields

Classics

The classics, in the Western academic tradition, refer to cultures of classical antiquity, namely the Ancient Greek and Roman cultures. The study of the classics is considered one of the cornerstones of the humanities; however, its popularity declined during the 20th century. Nevertheless, the influence of classical ideas in many humanities disciplines, such as philosophy and literature, remains strong.

Outside of its traditional and academic meaning, the "classics" can be understood as including foundational writings from other major cultures. In other traditions, classics would refer to the Hammurabi Code and the Gilgamesh Epic from Mesopotamia, the Egyptian Book of the Dead, the Vedas and Upanishads in India and various writings attributed to Confucius, Lao-tse and Chuang-tzu in China.

History

History is systematically collected information about the past. When used as the name of a field of study, history refers to the study and interpretation of the record of humans, societies, institutions, and any topic that has changed over time. Knowledge of history is often said to encompass both knowledge of past events and historical thinking skills.

Traditionally, the study of history has been considered a part of the humanities. In modern academia, history is occasionally classified as a social science.

Languages

The study of individual modern and classical languages forms the backbone of modern study of the humanities.

While the scientific study of language is known as linguistics and is a social science, the study of languages is still central to the humanities. A good deal of twentieth-century and twenty-first-century philosophy has been devoted to the analysis of language and to the question of whether, as Wittgenstein claimed, many of our philosophical confusions derive from the vocabulary we use; literary theory has explored the rhetorical, associative, and ordering features of language; and historians have studied the development of languages across time. Literature, covering a variety of uses of language including prose forms (such as the novel), poetry and drama, also lies at the heart of the modern humanities curriculum. College-level programs in a foreign language usually include study of important works of the literature in that language, as well as the language itself.

Law

In common parlance, law means a rule which (unlike a rule of ethics) is capable of enforcement through institutions. The study of law crosses the boundaries between the social sciences and humanities, depending on one's view of research into its objectives and effects. Law is not always e

Body shape

Human body shape is a complex phenomenon with sophisticated detail and function. The general shape or figure of a person is defined mainly by skeletal structure, muscles and fat. Skeletal structure grows and changes only up to the point at which a human reaches adulthood and remains essentially the same for rest of his or her life.

During puberty, differentiation of the male and female body occurs for the purposes of reproduction. In adult humans, muscle mass may change due to exercise, and fat distribution may change due to hormone fluctuations. Inherited genes play a large part in the development of body shape.

Body shape has effects on body posture and gait, and has a major role in physical attraction. This is because a body's shape implies an individual's hormone levels during puberty, which implies fertility, and it also indicates current levels of sex hormones. A pleasing shape also implies good health and fitness of the body. The art of figure drawing defines body proportions that are considered ideal.

Skeletal structure

Skeletal structure frames the overall shape of the body and does not alter much over a lifetime. Males are generally taller, but body shape may be analyzed after normalizing with respect to height.

Broad shoulders and expanded chest (in males):
Widening of the shoulders occurs as part of the male pubertal process. Expansion of the ribcage is caused by the effects of testosterone during puberty. Hence males generally have broad shoulders and expanded chests, allowing them to inhale more air to supply their muscles with oxygen.
Wide hips (in females):
Widening of the hip bones occurs as part of the female pubertal process, and estrogen (the predominant sex hormone in females) causes a widening of the pelvis as a part of sexual differentiation. Hence females generally have wider hips, permitting childbirth. Because the female pelvis is flatter, more rounded and proportionally larger, the head of the fetus may pass during childbirth. The sacrum in females is shorter and wider, and also directed more toward the rear (see image). This affects their walking style, resulting in hip sway; also, females generally stand with hips relaxed to one side.

After puberty, female hips are generally wider than female shoulders; males exhibit the opposite configuration. But not everyone follows this stereotypical pattern of secondary sex characteristics. Both male and female hormones are present in the human body, and though only one of them is predominant in an adult, the other hormone has effects on body's shape to some extent.

Facial features

Due to the action of testosterone, males develop these facial-bone features during puberty:

  • A more prominent brow bone.
  • A heavier jaw.
  • More prominent chin.
  • Larger nose bone.

Because females have around 20 times less testosterone, these features do not develop to the same extent. Hence female faces are generally more similar to those of pre-pubertal children.

Fat distribution, muscles and tissues

Body shape is affected by body fat distribution, which is correlated to current levels of sex hormones. Muscles and fat distribution may change from time to time, unlike bone structure, depending on food habits, exercises and hormone levels.

Fat distribution

Estrogen causes fat to be stored in the buttocks, thighs, and hips in women. When women reach menopause and the oestrogen produced by ovaries declines, fat migrates from their buttocks, hips and thighs to their waists; later fat is stored in the belly. Thus females generally have relatively narrow waists and large buttocks, and this along with wide hips make for a wider hip section and a lower waist-hip ratio compared to men.

Estrogen increases fat storage in the body, which results in more fat stored in the female body. Body fat percentage recommendations are higher for females, as this may serve as an energy reserve for pregnancy. Males have less subcutaneous fat in their faces due to the effects of testosterone; testosterone also reduces fat by aiding fat metabolism. Males generally deposit fat around waists and From Yahoo Answers

Question:What is a positive and negative feedback mechanism in the human body and Describe it, please give examples also

Answers:A positive feedback mechanism in the body is relatively rare. The two best described are defecation and childbirth. It is defined as a mechanism whose output stimulates an increase in output (i.e. birth). Also, "A system's response to external stimuli leading to further changes that serve to reinforce the initial response, thereby creating and accelerating a cause and effect loop." This mechanism is potentially dangerous because it will cause the body to respond as strong as it can until there is a release of stimulation (birth or uterine rupture). A negative feedback mechanism is one where the output causes a decrease in subsequent output (a balancing loop). There are lots of negative feedback loops in the body as this is the way that most systems maintain homeostasis ("The ability or tendency of an organism or cell to maintain internal equilibrium by adjusting its physiological processes.") A negative loop could be hormone secretion. Hormone levels decrease so the body stimulates the organ to produce more. At a certain level, the body recognizes that there is too much and pulls back production (the negative feedback).

Question:

Answers:Negative Feedback will prevent something from becoming excessive, Positive feedback will encourage it. An example is oxytocin during uterine contractions for positive feedback and for negative feedback, consider blood vessels which send signals to the brain if blood pressure is getting to high. The brain sends signals back to the blood vessels and heart (the effectors) and the blood vessels vasodilate (increase in diameter) because the heart rate decreases.This causes blood pressure to decrease. So its negative feedback, it causes something to stop or decrease, it does not encourage a process but rather inhibits it (ex. it prevents blood pressure from increasing too much). I really hope that makes sense.

Question:Apply the concept of a negative feedback mechanism to a process within the human body.

Answers:Check the link below. I promise that it's easy to read, so you won't have to work much.

Question:Please help me...this is the question........... give examples of ways that the skeletal, muscular, circulatory and nervous systems work together to maintain the human body. use all 4 systems ~how do they work together?? plz give me as many examples as u can!! ~ ~tyvm :)

Answers:This is a difficult question to ask. However, i would go for a simple solution. Think about eating food (ingestion, digestion, absorbtion and elimination). You pick up food, say an apple, and your brain sends signals through neurons that connects to the muscles and the muscles then contract lifting the skeletal structure of the arm, allowing the apple to be placed between the teeth. Muscles in the jaw then chew and grind the apple piece and it is swallowed down the esophagus by the process of perestalsis which involves nervous system control. It then reaches the stomach which contracts and churns mixing food stuff with gastric juices. It reaches the small intestine eventually and absorption of nutrients - this requires a huge demand of blood (controlled delivery to the small intestine of this blood happens thanks to sphincters and the circulatory system. (bearing in mind that all the actions above required involvement of the circulatory system). This is a simplistic overview but i think the example gives a good general involvement of all systems at work Hope this helps.

From Youtube

Just the Facts: The Human Body Trailer :Just the Facts: The Human Body The Musculoskeletal System Without its skeleton, the human body would be a shapeless bag of flesh. Without muscles, it would be as immobile as a tree. Together, the skeleton, joints and muscles of the human body create an astounding array of motion, form the graceful movements of a ballerina, to the powerful strides of an athlete, to the intricate precision of a musician's fingers. This first part of The Human Body series examines the structure of our skeleton and the function of our muscles. Viewers learn how our bones provide the rigid support necessary to hold any position, while our joints give us the remarkable range of motion needed to run, dance, climb, or simply to walk, sit and bend. In addition, we discover how our muscles and associated tendons and ligaments are constructed to allow them to change shape functions, as well as how bone growth occurs. This video also takes viewers on a tour of the most wondrous part of the skeleton, the skull, seemingly a solid bone with teeth, but actually far more than that. The program also explores the amazing human hand one of the most versatile structures among all species because it performs a most versatile structures among all species because it performs a remarkable range of tasks, from wielding a hammer to playing a Mozart sonata. Our feet, ankles and knees are also constructed to perform multiple tasks and endure incredible stress over the course of a lifetime. With commentary form ...