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In biology, homeostasis is the state of steady internal, physical, chemical, and social conditions maintained by living systems. This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits. Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life.
Physiology is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical and physical functions in a living system. According to the classes of organisms, the field can be divided into medical physiology, animal physiology, plant physiology, cell physiology, and comparative physiology.
Stress, either physiological, biological or psychological, is an organism's response to a stressor such as an environmental condition. Stress is the body's method of reacting to a condition such as a threat, challenge or physical and psychological barrier. There are two hormones that an individual produces during a stressful situation, these are well known as adrenaline and cortisol. There are two kinds of stress hormone levels. Resting (basal) cortisol levels are normal everyday quantities that are essential for standard functioning. Reactive cortisol levels are increases in cortisol in response to stressors. Stimuli that alter an organism's environment are responded to by multiple systems in the body. In humans and most mammals, the autonomic nervous system and hypothalamic-pituitary-adrenal (HPA) axis are the two major systems that respond to stress.
Senescence or biological aging is the gradual deterioration of functional characteristics in living organisms. The word senescence can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence involves an increase in death rates and/or a decrease in fecundity with increasing age, at least in the latter part of an organism's life cycle.
Life extension is the concept of extending the human lifespan, either modestly through improvements in medicine or dramatically by increasing the maximum lifespan beyond its generally-settled limit of 125 years. Several researchers in the area, along with "life extensionists", "immortalists" or "longevists", postulate that future breakthroughs in tissue rejuvenation, stem cells, regenerative medicine, molecular repair, gene therapy, pharmaceuticals, and organ replacement will eventually enable humans to have indefinite lifespans (agerasia) through complete rejuvenation to a healthy youthful condition. The ethical ramifications, if life extension becomes a possibility, are debated by bioethicists.
Longevity may refer to especially long-lived members of a population, whereas life expectancy is defined statistically as the average number of years remaining at a given age. For example, a population's life expectancy at birth is the same as the average age at death for all people born in the same year.
Maximum life span is a measure of the maximum amount of time one or more members of a population have been observed to survive between birth and death. The term can also denote an estimate of the maximum amount of time that a member of a given species could survive between birth and death, provided circumstances that are optimal to that member's longevity.
The Gaia hypothesis, also known as the Gaia theory, Gaia paradigm, or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating, complex system that helps to maintain and perpetuate the conditions for life on the planet.
Hormesis is a characteristic of many biological processes, namely a biphasic or triphasic response to exposure to increasing amounts of a substance or condition. Within the hormetic zone, the biological response to low exposures to toxins and other stressors is generally favorable. The term "hormesis" comes from Greek hórmēsis "rapid motion, eagerness", itself from ancient Greek hormáein "to set in motion, impel, urge on", the same Greek root as the word hormone. The term 'hormetics' has been proposed for the study and science of hormesis.
Biogerontology is the sub-field of gerontology concerned with the biological aging process, its evolutionary origins, and potential means to intervene in the process. The term "biogerontology" was coined by S. Rattan, and came in regular use with the start of the journal BIOGERONTOLOGY in 2000. It involves interdisciplinary research on the causes, effects, and mechanisms of biological aging. Biogerontologist Leonard Hayflick has said that the natural average lifespan for a human is around 92 years and, if humans do not invent new approaches to treat aging, they will be stuck with this lifespan. James Vaupel has predicted that life expectancy in industrialized countries will reach 100 for children born after the year 2000. Many surveyed biogerontologists have predicted life expectancies of more than three centuries for people born after the year 2100. Other scientists, more controversially, suggest the possibility of unlimited lifespans for those currently living. For example, Aubrey de Grey offers the "tentative timeframe" that with adequate funding of research to develop interventions in aging such as strategies for engineered negligible senescence, "we have a 50/50 chance of developing technology within about 25 to 30 years from now that will, under reasonable assumptions about the rate of subsequent improvements in that technology, allow us to stop people from dying of aging at any age". The idea of this approach is to use presently available technology to extend lifespans of currently living humans long enough for future technological progress to resolve any remaining aging-related issues. This concept has been referred to as longevity escape velocity.
Allostasis is the efficient regulation required to prepare the body to satisfy its needs before they arise by budgeting those needed resources such as oxygen, insulin etc., as opposed to homeostasis, in which the goal is a steady state. Allostasis, stability through variation, was proposed by Peter Sterling and Joseph Eyer in 1988 as a new model of physiological regulation. The goal of every living being is to “find and maintain a steady state for survival” which is achieved through allostasis and homeostasis. The term allostasis is used more frequently now since it is more inclusive of the idea that not everything in the body is in a single steady state meaning that there are varying levels of energy.
Enantiostasis is the ability of an open system, especially a living organism, to maintain and conserve its metabolic and physiological functions in response to variations in an unstable environment. Estuarine organisms typically undergo enantiostasis in order to survive with constantly changing salt concentrations. The Australian NSW Board of Studies defines the term in its Biology syllabus as "the maintenance of metabolic and physiological functions in response to variations in the environment".
Enquiry into the evolution of ageing, or aging, aims to explain why a detrimental process such as ageing would evolve, and why there is so much variability in the lifespans of organisms. The classical theories of evolution suggest that environmental factors, such as predation, accidents, disease, and/or starvation, ensure that most organisms living in natural settings will not live until old age, and so there will be very little pressure to conserve genetic changes that increase longevity. Natural selection will instead strongly favor genes which ensure early maturation and rapid reproduction, and the selection for genetic traits which promote molecular and cellular self-maintenance will decline with age for most organisms.
In neuroscience, homeostatic plasticity refers to the capacity of neurons to regulate their own excitability relative to network activity. The term homeostatic plasticity derives from two opposing concepts: 'homeostatic' and plasticity, thus homeostatic plasticity means "staying the same through change".
Ovotransferrin (conalbumin) is a glycoprotein of egg white albumen. Egg white albumen is composed of multiple proteins, of which ovotransferrin is the most heat reliable. It has a molecular weight of 76,000 daltons and contains about 700 amino acids. Ovotransferrin makes up approximately 13% of egg albumen. As a member of the transferrin and metalloproteinase family, ovotransferrin has been found to possess antibacterial and antioxydant and immunomodulatory properties, arising primarily through its iron (Fe3+) binding capacity by locking away a key biochemical component necessary for micro-organismal survival. Bacteria starved of iron are rendered incapable of moving, making ovotransferrin a potent bacteriostatic.
Ageing is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In a broader sense, ageing can refer to single cells within an organism which has ceased dividing, or to the population of a species.
The antagonistic pleiotropy hypothesis was first proposed by George C. Williams in 1957 as an evolutionary explanation for senescence. Pleiotropy is the phenomenon where one gene controls for more than one phenotypic trait in an organism. A gene is considered to possess antagonistic pleiotropy if it controls more than one trait, where at least one of these traits is beneficial to the organism's fitness early on in life and at least one is detrimental to the organism's fitness later on due to a decline in the force of natural selection. The theme of G.C. William's idea about antagonistic pleiotropy was that if a gene caused both increased reproduction in early life and aging in later life, then senescence would be adaptive in evolution. For example, one study suggests that since follicular depletion in human females causes both more regular cycles in early life and loss of fertility later in life through menopause, it can be selected for by having its early benefits outweigh its late costs.
In biology, energy homeostasis, or the homeostatic control of energy balance, is a biological process that involves the coordinated homeostatic regulation of food intake and energy expenditure. The human brain, particularly the hypothalamus, plays a central role in regulating energy homeostasis and generating the sense of hunger by integrating a number of biochemical signals that transmit information about energy balance. Fifty percent of the energy from glucose metabolism is immediately converted to heat.
Anthony Joonkyoo "Joon" Yun is a Korean-American physician, hedge-fund manager and investor.
Thomas A. Rando is an American stem cell biologist and neurologist, best known for his research on basic mechanisms of stem cell biology and the biology of aging. He is the Director of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research and a professor of Neurology and Molecular, Cell and Developmental Biology at the University of California, Los Angeles. Prior to joining the UCLA faculty, he served as Professor of Neurology and Neurological Sciences at Stanford University School of Medicine, where he was also founding director of the Glenn Center for the Biology of Aging. His additional roles while at Stanford included co-founder and deputy director of the Stanford Center on Longevity, founding director of Stanford's Muscular Dystrophy Association Clinic, and Chief of Neurology at the VA Palo Alto Health Care System.
References
- ↑ Anthony Joonkyoo Yun, MD (2014). Hiding in Plain Sight: Essays by Joon Yun, MD, Second Edition. p. 130. ISBN 9781312492028.
- ↑ "After the last death: Doctors, academics debate the possibility, value of a 150-year lifespan". Palo Alto Online. January 9, 2015. Retrieved January 13, 2015.
- ↑ Novoseltsev VN, Novoseltseva J, Yashin AI (2001). "A homeostatic model of oxidative damage explains paradoxes observed in earlier aging experiments: a fusion and extension of older theories of aging". Biogerontology. 2 (2): 127–38. doi:10.1023/a:1011511100472. PMID 11708379. S2CID 6542650.
- ↑ Rolls BJ, Phillips PA (March 1990). "Aging and disturbances of thirst and fluid balance". Nutr Rev. 48 (3): 137–44. doi:10.1111/j.1753-4887.1990.tb02915.x. PMID 2406645.
- ↑ Phillips, Paddy A.; Hodsman, G. Peter; Johnston, Colin I. (January 1991). "Neuroendocrine mechanisms and cardiovascular homeostasis in the elderly". Cardiovascular Drugs and Therapy. 4 (S6): 1209–1213. doi:10.1007/BF00114221. PMID 2009244. S2CID 32343396.
- ↑ "FAQ – Palo Alto Longevity Prize". Palo Alto Longevity Prize. Retrieved October 1, 2014.
- ↑ Ashlee Vance (September 9, 2014). "Silicon Valley Investor Backs $1 Million Prize to End Death". Bloomberg Businessweek . Retrieved October 1, 2014.
- ↑ "$1 Million Longevity Prize Seeks To "Hack The Aging Code"" (Press release). Yahoo! Finance. September 9, 2014. Retrieved October 1, 2014.
- ↑ Aaron Kinney (September 14, 2014). "Silicon Valley launches another bid to 'hack' aging, cheat death". San Jose Mercury News . Retrieved October 1, 2014.
- ↑ Victoria Thorp (November 23, 2014). "The Palo Alto Prize: A 'Moonshot' at Increasing Longevity". Palo Alto Pulse. Retrieved December 8, 2014.