Michigan State University researcher Kevin Haudek is the lead investigator of a three-year, $485,000 National Science Foundation that develops learning progressions and evaluates principle-based reasoning in undergraduate physiology students.

Principle-based reasoning is a practice of mind used by scientists to approach problems and constrain the boundaries of problems.

We believe that using such principles will help students think more like a scientist, said Haudek, an assistant professor in the MSU Department of Biochemistry and Molecular Biology in the College of Natural Science.

When students are able to demonstrate principle-based reasoning, they are capable of accurately predicting outcomes to disturbances of a system. Too often, the reliance on rote memorization rather than principle-based reasoning to solve problems, leads to context-bound thinking that fails to build robust understandings, which limits students ability to excel in the sciences.

The project is a cross-disciplinary collaboration between MSU researchers Joyce Parker in the Department of Earth and Environmental Sciences, John Merrill in the Department of Microbiology and Molecular Genetics, Mark Urban-Lurain in the CREATE for STEM Institute at MSU and researchers at the University of Washington.

The grant proposes to create the first learning progression in undergraduate physiology focusing on flux and mass balances core concepts.

Our learning progression will guide the creation of assessments instructors can use to determine where their students are along the spectrum of understanding, Haudek said.

When designing assessments, researchers and instructors must choose between constructed response and multiple-choice formats. Haudek noted the project will focus on the development of CR assessments and the evaluation of these assessments using computerized scoring methods.

We believe CR assessments have certain advantages, which is why wed like to develop these types of assessment items and framed in a whole new content area, he said.

Another aim of the grant is to begin to gather information about national trends in student learning of physiology during two and four-year programs.

The results of this aim may indicate that some gaps or plateaus of improvement might exist over the course of a curricular program, Haudek said.

Haudek and his colleagues are hopeful the project will positively impact a variety of science-based programs since physiology intersects with so many other degrees and career paths.

Although the project is not structured for the purpose of specifically addressing issues related to curricular gaps, Haudek said, one outcome of the study may be that some departments and programs become more self-reflective in the way students understanding of course content is evaluated, thus prompting changes in instruction, courses and or programs."

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NSF grant supports project to improve undergraduate physiology curriculum - MSUToday

The white supremacist and neo-Nazi protesters in Charlottesville, Virginia, hold vile and abhorrent views, and they should be condemned in the strongest terms by all political, business, and civic leaders. That these poisonous views spilled over into the killing of Heather Heyer shows how odious ideas can metastasize through a crowd. But before hatred manifests into violence, it must first be conceived, processed and perceived in the brain. Understanding the physiological and evolutionary underpinnings of hate within this organ might offer clues as to what drove the protesters in Charlottesville to act in such a repulsive manner.

The brain has a circuit that activates when it processes hatred. In neuroscience parlance, this circuit is composed of the right putamen, medial frontal gyrus, premotor cortex and medial insula, according to a University College London study, in which researchers scanned the brains of participants as they looked at images of those they professed to hate. The researchers discovered that these brain regions show significant activity. Parts of this hate circuit are also known to activate during acts of aggression. It isnt remarkable that hatred and hostility share similar neural correlates. But its physiological evidence that the distance between scorn and savagery can be measured not just in the size of crowds but the pathways of neurons. When David Duke explicitly and Donald Trump tacitly stoke hatred, they may be triggering the brains hate circuit which can readily crackle into violent behavior.

The hate circuit may even override empathy. In a study by Stanford neuroscientist David Eagleman, the brains of participants were scanned while they watched as six hands on a screen were randomly swabbed with cotton or stabbed with a needle. When people witnessed the hands that were punctured by the syringe, the regions of their brains associated with pain activated. They felt empathy. The study was then replicated and each hand was displayed with a one-word religious label such as atheist, Christian, Jew or Muslim. When participants saw the hands being stabbed of those who shared their religious affiliations, their brains on average showed more activity in the regions known for empathy. Even atheists were more empathetic towards fellow atheists. As concludes Eagleman in his book The Brain: The Story of You: Its about which team youre on.

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Related: My life as a white supremacist

White supremacists clash with counterprotesters at a rally in Charlottesville, Virginia, on August 12. Joshua Roberts/Reuters

While people have historically formed teams to survive, such tribalism can dull empathy and fuel hatred towards others. The white supremacists and other right wing extremists who mobilized in Charlottesville were demonstrating hate. But they are hateful and angry because theyre afraid. They fear that their team is losing significance in our country. A majority of children in the United States will be non-white by 2020. The overall non-white minority is projected to increase from 38 percent of the total population to 56 percent in 2060. The white supremacists are troubled by the rise of the other teams such as minorities and immigrants and may resort to violence in order to spread fear.

When President Donald Trump doesnt outright reject the white nationalist worldview, he implicitly condones those who have brains full of hate. When he retweets the opinions of white supremacists, he further stokes intolerance. When he castigates immigrants and implements religious-based travel bans, he provokes xenophobia and an us against them mentality. And because we increasingly see ourselves on different teams, its ever more difficult for our brains to register empathy towards each other.

As our leader, President Trump has a moral responsibility to do more to call out and condemn bigotrybefore it creates greater barriers between Americans. Throughout history, hatred has resulted in internecine battles that have splintered countries, the United States included. With a hateful brain, its almost impossible to obtain what we most needan open mind.

Deepak Chopra and Kabir Sehgal created Home: Where Everyone Is Welcome, a book of poems and album of songs inspired by American immigrants.

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Your Brain on Hate: Charlottesville, Trump and the Physiology of Loathing - Newsweek

A lecturer at the Ambrose Alli University has given students and fellow lecturers a night to remember after he proposed to his girlfriend at a school dinner.

The lecturer identified as Ernest Nwoke is the Head of Department (HOD) of Physiology in the prestigious school.

NAIJ.com gathered that the lecturer was once married but he lost his wife years ago.

AAU's Physiology HOD proposes to his girlfriend during his students' dinner

He found love again in the young lady who he proposed to on the night of a school dinner for his students.

It was gathered that Nwoke surprised his girlfriends by getting down on one the knee to propose in the midst of other lecturers and students in attendance.

The couple embraced each other after the lady accepted Nwokes romantic proposal.

Meanwhile, NAIJ.com TV went to the street to ask people what men want from women:

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AAU's Physiology HOD proposes to his girlfriend during students ... - NAIJ.COM

The head of Department of the Physiology Department, Ambrose Alli Unversity, Dr Ernest Nwoke, proposes to his girlfriend at the student dinner night.

It was a night to be remembered as the student and lecturers present were amazed with the expression of love be from the Pragmatic HOD, Dr Ernest Nwoke.

According to reports, Nwoke lost his wife and has found love again in the pretty young lady.

Congratulations to the couple.

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AAU Physiology HOD Proposes To Girlfriend At Student Dinner Night - Information Nigeria

Stanford University professor Maryam Mirzakhami, who recently came to my attention through her obituary, is the first and only woman to date to win the Fields Medal in Mathematics. She brings to my mind other women who were the first to win prestigious prizes and awards. Some of these firsts have occurred only recently. Match the woman with her accomplishment:

_____ 1. The first African-American to receive the Pulitzer Prize in Poetry.

_____ 2. The first black woman of any nationality to receive the Nobel Prize in Literature.

_____ 3. In 2010, 80 years after the first Oscars were awarded, she became the first woman to win the Academy Award for Best Director.

_____ 4. The first woman to receive the Nobel Prize in Economics.

_____ 5. The first American woman to receive a Nobel Prize in the sciences.

In 1947, when biochemist Gerty Cori received the Nobel Prize in Physiology or Medicine, she became the first American woman to win a Nobel Prize in the sciences and the first woman to receive the Nobel Prize in Physiology or Medicine. Today, what is known as the Cori cycle (named after Gerty and her husband Carl) describes the metabolism of carbohydrates and is important to the understanding of diabetes. Her research on enzymes led to her being the first to demonstrate that a defect in an enzyme could be the cause of a human genetic disease. Cori experienced much discrimination during her career but achieved in spite of that discrimination and received many honors. In addition to being inducted into the National Womens Hall of Fame, features on the Moon and Venus have been named for her.

Author, poet and teacher Gwendolyn Brooks began writing at an early age, encouraged to do so by her mother. Her first poem was published when she was 13 and by 16, she had already published 75 poems. Much of her work reflected her life experiences in the inner city of Chicago. Her first book of poetry was published in 1945. In 1950, when she won the Pulitzer Prize for Poetry, she became the first African-American to receive that honor. Appointed to a position that is now called the Poet Laureate Consultant in Poetry to the Library of Congress, Brooks has also been inducted into the National Womens Hall of Fame.

The first black woman of any nationality to win the Nobel Prize in Literature, Toni Morrisons citation reads who in novels characterized by visionary force and poetic import, gives life to an essential aspect of American reality. Morrison has written novels, plays and operas, many dealing with the black experience in America. Earlier in her career, Morrison worked in the publishing business and ensured that works by black authors were published. Her 1977 book Song of Solomon brought her national attention. Beloved, her most celebrated novel and a bestseller, was published in 1987, received the Pulitzer Prize for fiction and was made into a film starring Oprah Winfrey and Danny Glover. Morrison spent many years on the faculty at Princeton University and has received multiple honorary degrees.

The first woman to receive the Nobel Prize in Economics, Elinor Ostroms citation reads for her analysis of economic governance, especially the commons. She received her Ph.D. in political science, unable to pursue economics as she had been denied admission to trigonometry. During her years at Indiana University and Arizona State University, Ostrom focused on issues related to collective action, trust and cooperative use in the management of common pool resources which include forests, parks, fisheries, grazing land and irrigation systems. Her later work involved human interaction with ecosystems. There is even a law named for her; Ostroms law reads A resource arrangement that works in practice can work in theory. Ostroms many honors in addition to the Nobel Prize include election to the National Academy of Sciences.

In 2010, eighty years after the first Oscars were awarded, Kathryn Bigelow became the first woman to win the Academy Award for Best Director. A director, producer and writer, Bigelow won the award for The Hurt Locker. Originally educated as a painter, Bigelow received her Bachelors in Fine Arts from the San Francisco Art Institute in 1972. Her masters degree in film was earned at Columbia University. Her first full-length feature was released in 1982. Bieglows mainstream films are generally characterized as action films. Her latest film for which she directed and produced, Detroit, is currently playing in theatres. She said There should be more women directing; I think theres just not the awareness that its really possible. It is.

Learn about more she-roes and celebrate amazing women. These women who achieved firsts are among the more than 850 women profiled in the book Her Story: A Timeline of the Women Who Changed America. I am proud to tell womens stories and write women back into history. I stand on their shoulders.

(Answers: 1-B, 2-C, 3-E, 4-D, 5-A)

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Physiology, study of the functioning of living organisms, animal or plant, and of the functioning of their constituent tissues or cells.

The word physiology was first used by the Greeks around 600 bce to describe a philosophical inquiry into the nature of things. The use of the term with specific reference to vital activities of healthy humans, which began in the 16th century, also is applicable to many current aspects of physiology. In the 19th century, curiosity, medical necessity, and economic interest stimulated research concerning the physiology of all living organisms. Discoveries of unity of structure and functions common to all living things resulted in the development of the concept of general physiology, in which general principles and concepts applicable to all living things are sought. Since the mid-19th century, therefore, the word physiology has implied the utilization of experimental methods, as well as techniques and concepts of the physical sciences, to investigate causes and mechanisms of the activities of all living things.

The philosophical natural history that comprised the physiology of the Greeks has little in common with modern physiology. Many ideas important in the development of physiology, however, were formulated in the books of the Hippocratic school of medicine (before 350 bce), especially the humoral theory of diseasepresented by a philosopher, Nemesius, in the treatise De natura hominis (4th century ce; On the Nature of Man). Other contributions were made by Aristotle and Galen of Pergamum. Significant in the history of physiology was the teleology of Aristotle, who assumed that every part of the body is formed for a purpose and that function, therefore, can be deduced from structure. The work of Aristotle was the basis for Galens De usu partium corporis humani (On the Usefulness of the Parts of the Body) and a source for many early misconceptions in physiology. The tidal concept of blood flow, the humoral theory of disease, and Aristotles teleology, for example, led Galen into a basic misunderstanding of the movements of blood that was not corrected until English physician William Harveys work on blood circulation in the 17th century.

The publication in 1628 of Harveys Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (An Anatomical Dissertation upon the Movement of the Heart and Blood in Animals) usually is identified as the beginning of modern experimental physiology. Harveys study was based only on anatomical experiments; despite increased knowledge in physics and chemistry during the 17th century, physiology remained closely tied to anatomy and medicine. In 1747 in Berne, Switzerland, Albrecht von Haller, eminent as anatomist, physiologist, and botanist, published the first manual for physiology. Between 1757 and 1766 he published eight volumes entitled Elementa Physiologiae Corporis Humani (Elements of Human Physiology); all were in Latin and characterized his definition of physiology as anatomy in motion. At the end of the 18th century, Antoine Lavoisier wrote about the physiological problems of respiration and the production of heat by animals in a series of memoirs that still serve as a foundation for understanding these subjects.

Physiology as a distinct discipline utilizing chemical, physical, and anatomical methods began to develop in the 19th century. Claude Bernard in France; Johannes Mller, Justus von Liebig, and Carl Ludwig in Germany; and Sir Michael Foster in England may be numbered among the founders of physiology as it now is known. At the beginning of the 19th century, German physiology was under the influence of the romantic school of Naturphilosophie. In France, on the other hand, romantic elements were opposed by rational and skeptical viewpoints. Bernards teacher, Franois Magendie, the pioneer of experimental physiology, was one of the first men to perform experiments on living animals. Both Mller and Bernard, however, recognized that the results of observations and experiments must be incorporated into a body of scientific knowledge, and that the theories of natural philosophers must be tested by experimentation. Many important ideas in physiology were investigated experimentally by Bernard, who also wrote books on the subject. He recognized cells as functional units of life and developed the concept of blood and body fluids as the internal environment (milieu intrieur) in which cells carry out their activities. This concept of physiological regulation of the internal environment occupies an important position in physiology and medicine; Bernards work had a profound influence on succeeding generations of physiologists in France, Russia, Italy, England, and the United States.

Mllers interests were anatomical and zoological, whereas Bernards were chemical and medical, but both men sought a broad biological viewpoint in physiology rather than one limited to human functions. Although Mller did not perform many experiments, his textbook Handbuch der Physiologie des Menschen fr Vorlesungen (1837) and his personal influence determined the course of animal biology in Germany during the 19th century.

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It has been said that, if Mller provided the enthusiasm and Bernard the ideas for modern physiology, Carl Ludwig provided the methods. During his medical studies at the University of Marburg in Germany, Ludwig applied new ideas and methods of the physical sciences to physiology. In 1847 he invented the kymograph, a cylindrical drum used to record muscular motion, changes in blood pressure, and other physiological phenomena. He also made significant contributions to the physiology of circulation and urine secretion. His textbook of physiology, published in two volumes in 1852 and 1856, was the first to stress physical instead of anatomical orientation in physiology. In 1869 at Leipzig, Ludwig founded the Physiological Institute (neue physiologische Anstalt), which served as a model for research institutes in medical schools worldwide. The chemical approach to physiological problems, developed first in France by Lavoisier, was expanded in Germany by Justus von Liebig, whose books on Organic Chemistry and its Applications to Agriculture and Physiology (1840) and Animal Chemistry (1842) created new areas of study both in medical physiology and agriculture. German schools devoted to the study of physiological chemistry evolved from Liebigs laboratory at Giessen.

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The British tradition of physiology is distinct from that of the continental schools. In 1869 Sir Michael Foster became Professor of Practical Physiology at University College in London, where he taught the first laboratory course ever offered as a regular part of instruction in medicine. The pattern Foster established still is followed in medical schools in Great Britain and the United States. In 1870 Foster transferred his activities to Trinity College at Cambridge, England, and a postgraduate medical school emerged from his physiology laboratory there. Although Foster did not distinguish himself in research, his laboratory produced many of the leading physiologists of the late 19th century in Great Britain and the United States. In 1877 Foster wrote a major book (Textbook of Physiology), which passed through seven editions and was translated into German, Italian, and Russian. He also published Lectures on the History of Physiology (1901). In 1876, partly in response to increased opposition in England to experimentation with animals, Foster was instrumental in founding the Physiological Society, the first organization of professional physiologists. In 1878, again due largely to Fosters activities, the Journal of Physiology, which was the first journal devoted exclusively to the publication of research results in physiology, was initiated.

Fosters teaching methods in physiology and a new evolutionary approach to zoology were transferred to the United States in 1876 by Henry Newell Martin, a professor of biology at Johns Hopkins University in Baltimore, Maryland. The American tradition drew also on the continental schools. S. Weir Mitchell, who studied under Claude Bernard, and Henry P. Bowditch, who worked with Carl Ludwig, joined Martin to organize the American Physiological Society in 1887, and in 1898 the society sponsored publication of the American Journal of Physiology. In 1868 Eduard Pflger, professor at the Institute of Physiology at Bonn, founded the Archiv fr die gesammte Physiologie, which became the most important journal of physiology in Germany.

Physiological chemistry followed a course partly independent of physiology. Mller and Liebig provided a stronger relationship between physical and chemical approaches to physiology in Germany than prevailed elsewhere. Felix Hoppe-Seyler, who founded his Zeitschrift fr physiologische Chemie in 1877, gave identity to the chemical approach to physiology. The American tradition in physiological chemistry initially followed that in Germany; in England, however, it developed from a Cambridge laboratory founded in 1898 to complement the physical approach started earlier by Foster.

Physiology in the 20th century was a mature science; during a century of growth, physiology became the parent of a number of related disciplines, of which biochemistry, biophysics, general physiology, and molecular biology are the most vigorous examples. Physiology, however, retains an important position among the functional sciences that are closely related to the field of medicine. Although many research areas, especially in mammalian physiology, have been fully exploited from a classical-organ and organ-system point of view, comparative studies in physiology may be expected to continue. The solution of the major unsolved problems of physiology will require technical and expensive research by teams of specialized investigators. Unsolved problems include the unravelling of the ultimate bases of the phenomena of life. Research in physiology also is aimed at the integration of the varied activities of cells, tissues, and organs at the level of the intact organism. Both analytical and integrative approaches uncover new problems that also must be solved. In many instances, the solution is of practical value in medicine or helps to improve the understanding of both human beings and other animals.

The anatomical and medical origins of physiology still are reflected in university courses and textbooks that concentrate on functional organ systems of animals (e.g., frog, dog, cat, and rat). The trend in physiology, however, is to emphasize function rather than structure. Hence, comprehensive functional specializations such as nutrition, transport, metabolism, and information have replaced earlier structural studies of organ systems. This trend can be explained in part by the fact that the analysis of an organ system typically involves studies at the levels of cells and molecules, and functional emphasis accommodates such studies better than the organ-system approach.

Early in the 20th century the emphasis on cells as units of function resulted in a view that all physiology is essentially cell physiology and that all teaching therefore should pivot around the properties of cells. In later years successful analyses of cellular mechanisms involving synthesis, control, and inheritance led to similar emphasis at a new and more fundamental level, the molecules that constitute cells. The study of physiology now encompasses molecules, cells, organs, and many types of animals, including humans. The comparisons resulting from such studies not only strengthen human physiology but also generate new problems that extend into evolution and ecology. Much of the impetus for comparative physiology resulted from the economic or medical importance to humans of parasites, insects, and fishes.

Most of the physiology of microorganisms and plants developed independently of animal physiology. The concept of comparative biochemistry provided the foundations for a physiology of microorganisms that extended beyond the parasitic forms that are of medical importance and resulted in recognition of the fundamental roles of microorganisms in the biosphere. Botanists and agriculturists explore the physiology of higher plants, but fundamental differences in the modes of life of animals and plants leave little common ground above the molecular and cellular levels. In a little-known textbook, Claude Bernard stated that there is only one way to live, only one physiology of all living things. The goal of general physiology is to abstract this single physiology from the physiologies of all types of organisms. Although common or general features usually are found at the cellular and molecular levels of organization, multicellular structures also are studied. Processes that underlie cell function are emphasized in an approach based on analyses in terms of physical and chemical principles.

In the late 19th century the principle of conservation of energy was derived in part from observations that fermentation and muscle contraction are essentially problems in energetics. Biological energetics began with studies that established the basic equation of respiration as:Fuel + oxygen carbon dioxide + water + heat. It was realized that the heat produced in fermentation and the work performed during muscle contraction must originate in similar processes and that fuel in the equation above is a source of potential energy. Early in the 20th century, studies of animal calorimetry verified these concepts in humans and other animals. Calorimetry studies showed that the energy produced by the metabolism of foodstuffs in an animal equals that produced by the combustion of these foodstuffs outside the body. After these studies, measurement of the basal metabolic rate (BMR) was used in the diagnosis of certain diseases, and data relating the composition of foodstuffs to their value as sources of metabolic energy were obtained.

Early in the 20th century it was established that measurable amounts of the carbohydrate glycogen are converted to lactic acid in frog muscles contracting in the absence of oxygen. This observation and studies of alcoholic fermentation confirmed that the energy for fermentation or muscle contraction depends on a series of reactions now known as glycolysis. In order to show that the conversion of glycogen to lactic acid could provide the necessary energy for muscular contraction, extremely delicate measurements of the heat produced by contracting muscles were required. As a result of glycolysis studies, adenosine triphosphate (ATP) was recognized as an important molecule in cellular energy transfer and utilizatione.g., movement, generation of electricity, transport of materials across cell membranes, and production of light by cells. Soon it was discovered that a muscle protein called myosin acts as an enzyme (organic catalyst) by liberating the energy stored in ATP and that ATP in turn can modify the physical properties of myosin molecules. It was also shown that a muscle fibre has an elaborate and ordered structure, which is based on a precise arrangement of myosin and another muscle protein called actin.

Glycolysis is an anaerobic process (i.e., it does not require oxygen) and may represent one of the oldest mechanisms for cellular energy transfer, since the process could have evolved before there was free oxygen in Earths atmosphere. Most cells, however, derive their energy from a series of reactions involving oxygen and called the tricarboxylic acid cycle (Krebs cycle, or citric acid cycle). The enzymes for the cycle are part of the structure of a mitochondrion, which is an elaborate cellular component filled with membranes, generally shaped like a bean. In the course of the oxidation, three molecules of energy-rich ATP are generated for each oxygen atom used to form a molecule of water. The mitochondrion, therefore, is the cellular site of respiratory combustion first clearly demonstrated in whole animals by Lavoisier.

The ultimate source of foodstuffs used by animals is plants. Early 19th-century studies of photosynthesis were closely related to those of respiration and began with Joseph Priestleys demonstration that plants could restore the air used during respiration or combustion. The most important equations for living things therefore, are mutually inverse. In respiration:(CH2O)n + nO2 nCO2 + nH2O + heat. carbo-oxygen carbon water hydrate dioxide In photosynthesis:nCO2 + nH2O + light (CH2O)n + nO2.

In the 1930s, it was shown that photosynthesis involves splitting hydrogen from water and that the oxygen liberated in photosynthesis comes from water. During the light reactions, light energy is captured by a green pigment called chlorophyll and used to generate reactive hydrogen and ATP that are used during dark reactions in which carbohydrates and other cell constituents are synthesized.

The classical fields of organ-system physiology have a role subsidiary to that of cellular metabolism. Feeding and digestion, for example, become a means for the enzyme-catalyzed breakdown of organic compounds into relatively small molecules that can be transported readily; nutrition, therefore, is a way to supply animals with sufficient sources of energy and specific substances that they cannot synthesize. Comparative animal studies, which were of practical importance in the discovery of some vitamins, led also to the general observation that the specific nutrient requirements of animals are consequences of a slow evolutionary deterioration in which synthetic abilities are lost through changes or mutations in hereditary material.

Nutrition and digestion, however, also have been important in obtaining information at the cellular and molecular levels. It was through studies of digestion, for example, that the existence and nature of enzymes were first disclosed clearly. In addition, early recognition of similarities between digestion and fermentation foreshadowed knowledge of the important role of fermentation in cellular metabolism. Finally, the study of vitamin nutrition was closely integrated with that of cellular oxidation, in which certain vitamins play an essential catalytic role.

In intact organisms, the chemical activities of individual cells do not interfere with the functions of the organism. Much of the study of physiology is concerned with the ways by which cells obtain their nutrients and dispose of their waste products. Knowledge of the mechanism of protein synthesis and its connections with inheritance and cellular control mechanisms have initiated new inquiries into functions at all levels (i.e., cells, organs, and organisms).

Many important advances in surgery and medicine have been based on the physiology of circulation, which was first studied in 1628. The measurement of blood pressure, for example, was introduced on a practicable basis late in the 19th century and has become an important part of medical diagnosis. The physiology of circulation is concerned with the origin of blood pressure in the force of the heartbeat and the regulation of heart rate, blood pressure, and the flow of blood.

Variations in heart rate that led Aristotle to consider the heart as the seat of the emotions (an idea later proven incorrect) were among the phenomena whose explanation revealed the existence of the autonomic nervous system. More important to the circulatory system than variation in heart rate, however, is the ability of the heart to adjust the strength of its beat to meet certain demands of the body.

The peripheral control of blood pressure and blood flow depends upon a maze of interacting control mechanisms, the most significant of which are in direct control of the diameter of small arterial branches that enlarge or dilate in response to chemical products formed during metabolism. Increased metabolic activity of tissues such as muscles or the intestine, therefore, automatically induces increased blood flow through the dilated vessels. This action, which could result in a fall in blood pressure, is offset by central-reflex controls that constrict arterial branches not dilated as a result of local chemical effects. Certain regions of the skin and the intestines serve as reservoirs for blood that may be diverted to muscles or the brain if necessary. Peripheral control may break down if excessive demands are made upon it in hot weather (heatstroke), during vigorous exercise after meals (muscle cramp), and after extensive loss of blood or tissue damage (shock) or extreme emotion with consequent activation of the autonomic nervous system (emotional shock). A remarkable adaptation occurs in air-breathing vertebratesreptiles, birds, and mammalswhich dive for food or protection. During a dive, the flow of blood to all parts of the body except the brain and the heart is reduced substantially. The energy for muscle contraction is provided by the anaerobic process of glycolysis because the oxygen in the blood goes to the brain and heart, which cannot function without a constant supply of oxygen.

Comparative studies have disclosed two major patterns in circulatory systems. Among vertebrates and a few invertebratesnotably annelid worms and cephalopod mollusksthe blood flows entirely in closed channels or vessels, never coming into direct contact with cells and tissues; blood pressure and the velocity of flow are high and relatively constant, and the volume of blood is small. In many invertebratesespecially arthropods and mollusks other than cephalopodsthe blood flows for part of its course in large sinuses or lacunae and comes directly into contact with the tissues. Blood pressure and the velocity of flow are low and variable in these invertebrates, and the large volume of blood is comparable to the total volume of all body fluids in vertebrates.

Consideration of the blood as a transport system has centred especially on the transport of oxygen and carbon dioxide. The colour of blood changes as it passes through the lungs: venous blood is dark purple and arterial blood is bright red because of the properties of a blood pigment called hemoglobin. Knowledge of the complete structure of hemoglobin has enabled scientists to study fundamental questions of heredity at the molecular level. The development of blood banks and the techniques involved in blood transfusion depend on knowledge of the physical, chemical, and biological properties of blood. These properties include a remarkable diversity of hemoglobin, both among individuals and species and also within an individual during development. In many instances variations in protein composition better adapt a species to its circumstances.

Studies of membrane transport at the cellular level are an important part of general physiology. Although quantitative theories of diffusion and osmosis that developed around 1900 were applied to cell physiology, a number of phenomena (e.g., movement through membranes of certain ions and other compounds of biological importance) did not behave according to established physical principles. As a result of studies of osmotic and ionic regulation in freshwater animals, the concept of active transport was formulated. Crucial to the acceptance of this concept were studies with frog skin, which can transport sodium ions against chemical and electrical forces; the transport, specific for sodium ions, is dependent on a continuing input of metabolic energy. Efforts have been directed toward establishing a molecular mechanism that may involve an enzyme found in surface membranes of cells. This enzyme breaks down ATP and releases the energy in the molecule only if sodium and potassium ions are present.

The physiology of animals differs from that of plants in the rapid response of animals to stimuli. French mathematician and philosopher Ren Descartes, responsible for the concept of the reflex that dominated neurophysiology for most of its history, thought a sensory impulse was reflected from the brain to produce a reaction in muscles. Later studies of the effects of ions on nerves suggested that a nerve must be surrounded by a membrane and that a nerve impulse results from a change in the ability of the membrane to allow passage of potassium ions. When it was shown that nerves are made up of thousands of tiny fibres, which are processes that extend from cells located in the brain or spinal cord, the nerve impulse hypothesis was applied to individual nerve fibres rather than to whole nerves. Electronic technology provided the techniques and giant nerve fibres of squids provided the experimental material that enabled two Nobel prize winners for physiology, Alan Lloyd Hodgkin and Andrew Fielding Huxley, to extend this hypothesis into a theory of the excitation of nerve cells in which sodium ions and potassium ions play principal roles.

The reflex concept, however, was not dependent on understanding the molecular basis of excitation, conduction, and transmission. Early in the 20th century the role of interaction of nervous centres in controlling muscle contractions was established. The reflex now is conceived as a unit in which nerve impulses initiated in sensory neurons or nerve cells are conducted to a centre in the brain or spinal cord. In the centre, impulses initiated in motor neurons are conducted to muscles and induce a reflex response. Two processes can occur in the centre; one is associated with central excitatory states, the other with central inhibitory states. The net effect of any stimulus or group of stimuli, therefore, can be interpreted as an interaction of these opposing states in the centre.

After the demonstration that the effects of the vagus nerve in slowing the heart are mediated by a chemical substance, subsequently identified as acetylcholine, the concept of chemical transmission of nervous impulses was extended to the central nervous system. Typically, transmission of excitation from cell to cell is accomplished by the liberation of a chemical transmitter from a nerve ending.

The reflex concept gave rise to premature attempts to develop a psychology based on reflexes. These attempts (behaviourism) were advanced by Russian scientist Ivan Pavlovs discovery of conditioned responses. Originally known as conditioned reflexes, these responses have been found in most animals with central nervous systems. More complex than simple reflexes, their mechanism has not yet been established with certainty.

The analysis of sensory functions also extends to the cellular level. Sense organs are diverse in structure and sensitivity to specific stimuli. It may be that the common molecular basis for the differences in sensitivity is a change in permeability of a special region of the membrane surrounding a sensory cell. This change in permeability could allow a nerve fibre to become excited and initiate a nerve impulse. Neurophysiology has borrowed from, and contributed to, the information theory used in communications engineering. The function of sense organs is to gather information both from the environment and the organism. The central nervous system integrates this information and translates it into a program of response involving the entire organism. In addition, the brain can store information previously received (memory) and has the ability to initiate actions without obvious external stimulation (spontaneity). Some aspects of memory and integrative function have been modelled in electronic computers; in fact the development of computers was closely connected with the development of ideas about the functions of the central nervous system.

The analytical interpretation of central nervous function remains, however, a complex and difficult field, even though recent progress has brought closer together the study of behaviour in terms of nerve function and behavioral models. Considerable effort has been directed to the localization of brain function. Although specific centres for reception of sensory information and integration of motor programs are known, the integrative functions that tie them together, as well as the functions of memory, are not so well established.

The concept of internal regulations is attributed to Claude Bernard, who thought of blood as an internal environment in which cells function; according to Bernard, maintenance of the internal environment at a constant level was a major responsibility of all body functions. Bernard showed in studies of the formation and breakdown of glycogen in the liver that internal organs can secrete materials into the blood. Other investigators demonstrated such a secretion and used the word hormone to describe the substance. One classical study concerned control of the secretion of digestive fluids by the pancreas; an active substance secretin was purified, as have been a number of similar materials from the digestive tract. The field of endocrinology now is a major part of physiology.

The endocrine system complements the nervous system in control and coordination. Hormones, liberated into blood and other body fluids by endocrine glands and transported throughout the body, usually act either on specific target organs or on certain activities of many organs. Nervous coordination most often is concerned with rapid responses of short duration; endocrine coordination, however, usually is involved in slower responses of longer duration. Stationary-state regulation, or homeostasis, depends on the action of hormones at many points. The hormones insulin and glucagon, both formed in specialized endocrine tissue in the pancreas, control the level of sugar in blood. Vasopressin from the pituitary gland at the base of the brain and aldosterone from the adrenal glands near the kidneys control salt and water balance of the blood. Hormonal regulation, however, is not confined to homeostasis. The cyclic events of the female reproductive cycles in mammals, for example, are determined by a complex sequence of endocrine interactions involving hormones of the pituitary gland and the ovary.

The pervasive regulatory action of hormones is part of a large system of interactions to which the term feedback generally is applied. Hormones involved in homeostatic regulation, for example, influence their own secretion. The secretion of certain steroid hormones, which have a significant action on the conversion of amino acids to glycogen, is controlled by another hormone called the adrenocorticotropic hormone (ACTH), which is formed in the anterior pituitary gland. In turn the secretion of ACTH is controlled by a releasing factor formed in the midbrain and liberated from the stalk of the pituitary gland. ACTH liberation normally is controlled by the concentration of steroids in the blood, so that an increase in steroid concentration inhibits ACTH secretion; this negative feedback, however, may be overcome in certain conditions of intense nervous stimulation.

A similar pattern of releasing factors, by which the nervous system interacts with the endocrine system, also is known for other anterior pituitary hormonese.g., those involved in the reproductive cycle and in responses of the thyroid gland to temperature changes. In addition, neurosecretory cellsnerve cells specialized for endocrine functionliberate hormones (e.g., vasopressin) that act directly on a specific target. Comparative studies show that neurosecretory cells are important in developmental and regulatory functions of most animals. Discrete endocrine glands, however, occur less frequently; in insects and crustaceans, cycles of growth, molting (shedding of the cuticle), and development are controlled by hormones. The identification of insect hormones may be useful in controlling pests through specific interference with processes of growth and development.

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physiology | Definition & Bodily Function | Britannica.com

Credit: ESA/NASA

The newest crewmember on the International Space Station, ESA astronaut Paolo Nespoli, has hit the ground running. After arriving in the early hours of 29 July and taking the rest of the day off, Paolo and the crew were back to work by 30 July.

First up on Paolo's schedule is a human physiology experiment using the Mares machine. The Muscle Atrophy Research and Exercise System, housed in Europe's Columbus laboratory module, is a three-in-one muscle-measuring machine that monitors astronauts' muscles as they work out.

Muscle strength decreases during spaceflight and researchers need to know why in order to prepare for long missions and safe space tourism.

The measurements are part of the Sarcolab-3 experiment that is assessing how weightlessness affects the calf and ankle muscles, the parts of the leg that carry the load of the rest of the body.

"This is important, as establishing the mechanisms involved in space-related muscle deterioration will help us to devise optimised countermeasures," says Thu Jennifer Ngo-Anh, head of ESA's Human Research Office.

Sarcolab-3 is a unique experiment, involving scientists from NASA, ESA and the Russian Institute of Biomedical Problems an example of international cooperation benefitting scientific research.

Watch a timelapse video of Mares being assembled, an all-day task in itself.

Explore further: Video: Vita docking

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Image: Astronaut Paolo Nespoli and the Mares human physiology ... - Phys.Org

Healthy juvenile plants of the endangered Cycas micronesica thrive in a deep understory habitat where they effectively utilize infrequent sunflecks. Credit: Thomas Marler

The living cycad species are among the world's most threatened plant groups, but are also among the world's least studied plant groups. The need for a greater understanding of basic physiology of cycads has been discussed for decades, yet to date the needed research is lacking.

Recent reports of how gymnosperms are more sluggish than angiosperms in the photosynthetic use of sunflecks in forest understory settings prompted an article from the University of Guam that appears in the current issue of the journal Plant Signaling & Behavior.

"The list of species used to represent gymnosperms in the conclusions on sunfleck use were restricted to conifers," said author Thomas Marler. "But the world's gymnosperms are also represented by three other groups of plants, and these were not included in the database that was used to formulate conclusions."

The Cycadidae, Ginkgoidae, and Gnetidae groups of plants are also gymnosperms, and collectively they contain close to 400 described species. Guiding principles are needed to improve the representation and relevance of these plants in contemporary research agendas.

According to Marler, the addition of more descriptive research targeting cycad species is welcomed regardless of the approach. But the adherence to protocols that ensure species relevance would improve the outcomes. Since forest canopy traits define sunfleck qualities, the experimental protocols for studying sunfleck use by newly studied species should be defined from the natural habitats of each species. Moreover, the behavior of cultivated plants often differs from that of plants in natural settings, and moving from the current level of minimal knowledge to a level of adequate knowledge may be reached most rapidly by studying these plants within their native range rather than in botanic gardens. A phenomenon called context dependency is also pertinent to the needed expansion of cycad research. Do environmental factors such as drought influence how a cycad plant capitalizes on the ephemeral access to sunflecks?

Attempts to link phylogenetic subsets of plants more closely to the broader global research agenda need to be accurate. Adding more physiology research to cycads would greatly improve our understanding of how the world's plants effectively utilize the pulses of sunlight that punctuate the forest sub-canopy.

Explore further: And one root said to the other root, 'Don't I know you from somewhere?'

More information: Thomas E. Marler, Increasing relevance of sunfleck research, Plant Signaling & Behavior (2017). DOI: 10.1080/15592324.2017.1334030

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Cycad leaf physiology research needed - Phys.org - Phys.Org

July 31, 2017

SCIENTISTS in the UK and India have discovered more evidence that positive stimuli in early childhood can benefit the infant brain.

A comparative study of genetic variations between two parts of the brain found evidence for progressive variations in the brain's genome benefiting physiological development.

And they believe such variations may be linked to the level of brain activity determined by so-called 'nurture' factors, which are environmental rather than hereditary.

"The implication is that early life positive experiences can stimulate cognitive activities and will favor such 'beneficial' variations, whereas, negative experiences or lack of cognitive stimulation can reduce the genomic diversity resulting in limiting brain capacity," said Dr Arijit Mukhopadhyay, a researcher in human genetics and genomics at the University of Salford.

It is one of the first studies to show the effect of brain activity on genomic changes, and is published in F1000 Research, Dr. Mukhopadhyay and colleagues from CSIR-Institute of Genomics & Integrative Biology, Delhi.

Dr. Mukhopadhyay explains: "It is generally assumed that as we inherit our genetic blueprint (DNA) from our parents, we also inherit the genetic variations alongside. While this is largely true, this research along with other reports in the recent literature shows that some variations - termed de novo somatic variations - occur as a normal process and are added to diversify our genetic repertoire.

The team collected two different parts of the human brain, frontal cortex and corpus callosum from multiple individuals, postmortem, from the Brain Bank, (the individuals died due to road accidents without any known disease.)

The researchers extracted DNA from the tissue and performed state-of-the-art genomic sequencing to identify genetic variations between the two. The study found a higher number of possibly 'beneficial' variations in the cortex compared to the corpus callosum of the same individuals.

Dr. Mukhopadhyay said: "This finding is an important step in our understanding of early brain development and of how local genetic variations can occur and shape our physiology.

"It is likely that genetic variations beyond those we inherit are important for our ability to adapt and evolve locally for specific organs and tissues.

"We believe our results indicate that such physiology driven genetic changes have a positive influence on the development of the neuronal connectivity early in life."

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Physiology-driven genetic changes have positive influence on brain development - News-Medical.net

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John Knight is senior lecturer in biomedical science; Yamni Nigam is associate professor in biomedical science; both at the College of Human Healthand Science, Swansea University.

Glands in the endocrine system produce a range of hormones that regulate our bodys activities by keeping substances such as blood glucose and electrolytes within their normal ranges. Like all other body systems, the endocrine system undergoes age-related changes that negatively affect its functioning. As a result of these changes, older people are more prone to disturbed sleep patterns, have a reduced metabolic rate, lose bone density, accumulate body fat, and show increases in blood glucose. As a consequence, they are at higher risk of health issues such as insomnia, fractures, type 2 diabetes and cognitive decline. This seventh article in our series about the effects of age on the body describes what happens, with advancing age, to endocrine glands and hormone production.

Knight J, Nigam Y (2017) Anatomy and physiology of ageing 7:the endocrine system. Nursing Times [online]; 113: 8, 48-51

The endocrine system works in conjunction with the nervous system to regulate, and coordinate the activities of, the bodys tissues and organs. It consists of a collection of glands located in different parts of the body the main ones being the pituitary, pineal, thyroid, parathyroids, adrenals, pancreas, ovaries and testes (Fig 1). These glands produce a variety of blood-borne chemical signals called hormones, which play an essential role in maintaining balance (homoeostasis) in the body, helping to ensure that variables such as blood glucose and electrolytes are kept within normal ranges.

fig 1 the effects of ageing on endocrine function

The pituitary gland, often referred to as the master gland, produces several major hormones and regulates the activity of many other endocrine glands. It is split into a posterior portion, which is formed from neural tissue extending from the hypothalamus, and an anterior portion, which is formed from epithelial cells derived from the roof of the oral cavity.

The anterior pituitary secretes growth hormone (somatotropin), which promotes the growth of bone, muscle and most of the major internal organs. In early childhood, somatotropin is secreted in relatively small amounts, but during the teenage years there is a marked increase in serum somatotropin levels corresponding to the growth spurts of puberty. Around the age of 25-30, somatotropin secretion begins to decline in both men and women. In men it is estimated to halve every seven years although there appears to be much variation between individuals (Gentili, 2015).

The decline in somatotropin secretion in later years is often referred to as the somatopause and is associated with a variety of physiological changes (Jonas et al, 2015; Veldhuis et al, 2005), including:

The somatopause can be hastened in people who lead a sedentary lifestyle and in those who already carry a high percentage of body fat. Conversely, in premeno-pausal women, oestrogen appears to slow its onset and progression (Gentili, 2015).

The exact causes of somatopause are yet to be fully established, however, the age-related decrease in somatotropin secretion mirrors the decrease of growth-hormone releasing hormone (GHRH) secretion by the hypothalamus. Recent research indicates that some of the negative physiological changes that come with declining levels of somatotropin can be reversed by growth hormone replacement therapy. In clinical trials, recombinant human growth hormone has been shown to improve lean muscle mass retention and quality of life scores in older people (Jonas et al, 2015).

The pineal gland is slightly smaller than a pea and resembles a small pine cone hence its name. Found in the diencephalon, towards the centre of the brain, it synthesises the hormone melatonin from the neurotransmitter serotonin. The pineal gland functions like an internal body clock: during the day, when there is a lot of light, melatonin secretion is inhibited, but as the day draws to a close and light diminishes, melatonin secretion increases, preparing the body for sleep.

As we age, the pineal gland undergoes a process of calcification, detectable even in young children. Melatonin levels progressively decrease: 60-year-olds have 80% less melatonin in their blood than teenagers. Some drugs commonly prescribed to older people, such as beta blockers and non-steroidal anti-inflammatory drugs, can reduce melatonin levels even further.

Decreased melatonin levels are linked to an increased prevalence of sleep disturbances and, in some people, may ultimately lead to geriatric insomnia (Bubenik and Konturek, 2011). Since sleep is essential for cognitive function, sleep disturbances can exacerbate age-related changes in the brain.

There is some evidence that exposure to bright light either sunlight or artificial light in the morning increases the speed of sleep onset by triggering an earlier release of melatonin in the evening. Similarly, the therapeutic use of prolonged-release melatonin has been shown to improve sleep onset time, sleep quality, morning alertness and quality of life in people aged 55 and over who have insomnia (Wade et al, 2007)

The thyroid gland plays a major role in controlling metabolism and adjusting blood calcium levels. The hormones it secretes regulate a number of physiological processes, including:

The thyroid secretes the iodine-containing hormones T4 (tetraiodothyronine, which is also known as thyroxine) and T3 (triiodothyronine), which largely control cellular metabolism. T4 is released in greater quantities than T3, the typical ratio being 15:1. T4 is then rapidly converted into the more biologically active T3, which is around three times more potent in terms of increasing the metabolic rate.

The clearance of T4 by the liver decreases with age, but this is offset by a gradual decline in T4 secretion, so T4 serum levels tend to remain constant. However, there is a clear age-related decrease in the levels of serum T3, as well as of thyroid-stimulating hormone (TSH) produced by the pituitary gland (Peeters, 2008; Chahal and Drake, 2007). This may contribute to the gradual reduction in basal metabolism that is apparent in many people in middle and old age (in which the decline in lean muscle mass described above also plays a role).

With advancing age, autoimmune reactions against ones own thyroid gland are commonly seen. Indeed, the presence, in older people, of antibodies specific to thyroid tissue is so common that it is often considered a normal age-related change. A high concentration of such antibodies may herald the onset of autoimmune hypothyroidism, a disease affecting up to 5% of the over-60s and associated with low metabolic rates, a tendency to put on weight and low core temperature. Since this condition is autoimmune in nature, women are at greater risk of developing it (this is true for most autoimmune diseases): up to eight times more women than men experience autoimmune hypothyroidism.

The results of thyroid function tests should be assessed carefully in older people, as common long-term conditions (such as chronic obstructive pulmonary disease, hypertension, diabetes and arthritis) and dieting can lead to reductions in circulating thyroid hormones, particularly the more active T3. This phenomenon of reduced thyroid function in the absence of thyroid disease is referred to as non-thyroidal illness. Similarly, many drugs used to treat long-term conditions in older people (for example, lithium and glucocorticoids) can supress thyroid function or reduce the activity of circulating thyroid hormones, leading to a reduction in metabolic rate (Peeters, 2008).

The thyroid gland also plays a role in calcium homoeostasis. When we consume foods rich in calcium, it releases calcitonin, which inhibits the activity of osteoclasts bone cells that break down bone tissue (bone is a dynamic tissue continually being built and broken down). By inhibiting osteoclast activity, calcitonin indirectly increases bone density.

Few studies have examined the effects of ageing on calcitonin production in humans. The most comprehensive study, dating back to 1980, demonstrated an age-related decline in calcitonin production in 50 healthy women aged between 20 and 69 years (Shamonki et al, 1980). This decline may partially explain the reduction in bone mass seen in most women as they grow older. However, a later study has contradicted these findings, showing that although women appear to have lower levels of calcitonin secretion than men, there is no clear age-related decrease in serum calcitonin concentration (Tiegs et al, 1986).

The posterior portion of the thyroid is the location of four tiny parathyroid glands, which secrete parathyroid hormone (PTH) whenever blood calcium levels fall. Since a normal concentration of calcium is essential to many physiological processes (including muscle contraction, nerve conduction and blood clotting), the reserves of calcium stored in the skeleton need to be mobilised. PTH triggersthe release of calcium from the bonesinto the blood by indirectly stimulating osteoclasts.

Several studies have shown that most people, as they grow older, have significantly increased levels of circulating PTH (Portale et al, 1997). This hyperparathyroidism may well be one of the main causes of the reduction in bone density commonly seen in middle and old age. Recent studies have also shown a potential link with other pathologies, particularly age-related cognitive decline and dementia (Braverman et al, 2009).

The endocrine regions of the pancreas (islets of Langerhans) regulate bloodglucose levels. Beta cells in the islets secrete insulin in response to increased blood glucose for example, after a carbohydrate-rich meal. Insulin binds to receptors present on most cells, triggering the uptake of glucose from the blood. Once inside the cells, glucose is either metabolised immediately to release energy, or stored and converted into glycogen.

Alongside race, genetic predisposition and a high body mass index, ageing is one of the many risk factors linked to the development of type 2 diabetes (Knight and Nigam, 2017). Ageing human cells become less sensitive to the effects of insulin. The most likely cause appears to be a reduction in the number of insulin receptors at the surface of cells. This gradual insulin resistance goes hand in hand with an increase in blood glucose concentrations.

As shown in a study of 6,901 non-diabetic people (Ko et al, 2006), fasting blood glucose levels rise by around 0.15mmol/L for each decade of life after the age of 20. Whether this rise is a normal age-related change or a sign of diabetes in its early stages is not always clear, but it is certainly seen in many older people with no other symptoms of diabetes.

With advancing age, the insulin-producing beta cells become less sensitive to the level of glucose in the blood, so higher blood glucose levels are needed to trigger insulin release. Since older peoples cells are less receptive to insulin, the pancreas often responds by producing more, leading to increased insulin levels in the blood (hyperinsulinaemia). This can put excessive stress on the beta cells, leading to their exhaustion.

Age-related depletion of the beta cell population in the pancreas also occurs as a result of increased programmed cell death (apoptosis) and a diminished ability of the pancreas to produce new cells. Beta cell exhaustion and depletion result in a drop of insulin secretion of up to 0.5% per year of life. Additionally, the clearance of insulin by the liver increases with age, so there is less insulin available to interact with cells and promote glucose uptake.

These age-related changes to insulin production, clearance and response contribute to the creation of a diabetogenic environment. This may partially explain why the risk of developing type 2 diabetes increases with age (Brown, 2012).

The accumulation of abdominal fat is a common feature of ageing, particularly in people who have a poor diet and/or a sedentary lifestyle. Many age-related changes to the endocrine system contribute to this accumulation of adipose tissue, including the somatopause, autoimmune hypothyroidism, insulin resistance, and reduced circulating sex hormones.

This abdominal fat accumulation is linked to heart disease, high blood pressure and type 2 diabetes. These conditions may occur in isolation or together in the form of metabolic syndrome (Gong and Muzumdar, 2012).

The two adrenal glands are located above the kidneys and each consists of two main regions: the adrenal medulla (inner region) and the adrenal cortex (outermost layer).

The adrenal medulla is the location of chomaffin cells, which secrete the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). These are the fight or flight hormones that prepare the body for activity when it is threatened or in a state of excitement. The effects of adrenaline and nor-adrenaline include:

Ageing is associated with a decline in the secretion of adrenaline, but adrenaline plasma levels remain relatively constant

as clearance by the kidneys is usually reduced. There is some evidence that older men secrete less adrenaline in response to acute stress than younger men (Seals and Esler, 2000).

The adrenal cortex synthesises a varietyof steroidal hormones from cholesterol, mainly aldosterone and cortisol.

Aldosterone is a mineralocorticoid that regulates plasma levels of sodium and potassium, and plays an important role in water balance and blood pressure control. Research has revealed an age-related decrease in serum aldosterone levels, effectively reducing the bodys ability to retain sodium.

Decreased aldosterone secretion may contribute to postural hypotension and the light-headedness that is often experienced by older people when they stand up. This is supported by research demonstrating significant reductions in serum aldosterone levels in older people when they are upright, as opposed to recumbent (Hegstad et al, 1983).

Since sodium attracts water into the cardiovascular system via osmosis, lower plasma sodium levels (hyponatraemia) can lead to reduced blood volume and blood pressure. Several medications commonly prescribed to older people such as opiates, non-steroidal anti-inflammatory drugs, diuretics and antidepressants can exacerbate hyponatraemia (Liamis et al, 2008). Blood volume and blood pressure may be further reduced by age-related increases in the secretion of atrial natriuretic hormone (ANH), a powerful diuretic produced by the heart (Miller, 2009).

Cortisol is a glucocorticoid and its release is triggered by biological stressors such as physical injury or starvation. It is a natural anti-inflammatory and plays an important role in the breakdown of protein and fat.

Research into how cortisol levels change with ageing is often contradictory. Initial studies suggested that there could be a 20-50% increase in the mean levels of cortisol secretion between the ages of 20 and 80 (Chahal and Drake, 2007). More recently, however, it has been shown that this is not necessarily true: in some people, cortisol secretion diminishes with age, in others levels remain relatively stable throughout life (Wolf, 2015).

There appears to be a link between increased cortisol levels, reduced bone density and increased risk of bone fracture. There is also growing evidence that a higher cortisol concentration can contribute to the loss of cells from the hippocampus, resulting in hippocampal atrophy. This is often associated with a reduction in cognitive function in older people (Chahal and Drake, 2007). Other studies have shown that age-related increases in cortisol may also be linked to memory loss and sleep disorders (Chahal and Drake, 2007; Wolf et al, 2005).

There is some evidence that exercising regularly and maintaining a low percentage of body fat may slow the onset of the somatopause, help maintain bone density and improve the control of blood glucose. Supplementation with synthetic growth hormone has recently been shown to increase lean muscle mass in older people. However, this kind of therapy is associated with many side-effects such as joint pain, oedema and impaired glucose tolerance (Jonas et al, 2015).

The most famous and most thoroughly researched hormone replacement therapies are those that are used to treat the complications of the menopause. These therapies will be explored in the next article in this series.

Braverman ER et al (2009) Age-related increases in parathyroid hormone may be antecedent to both osteoporosis and dementia. BioMed Central Endocrine Disorders; 9: 21, 1-10.

Brown JE (2012) The ageing pancreas. British Journal of Diabetes and Vascular Disease; 12: 3, 141-145.

Bubenik GA, Konturek SJ (2011) Melatonin and aging: prospects for human treatment Journal of Physiology and Pharmacology; 62: 1, 13-19.

Chahal HS, Drake WM (2007) The endocrine system and ageing. Journal of Pathology; 211: 2, 173-180.

Gentili A (2015) Growth hormone replacement in older men. Medscape.

Gong Z, Muzumdar RH (2012) Pancreatic function, type 2 diabetes, and metabolism in aging. International Journal of Endocrinology; 2012: 320482.

Hegstad R et al (1983) Ageing and aldosterone. American Journal of Medicine; 74: 3, 442-448.

Jonas M et al (2015) Aging and the endocrine system. Postpy Nauk Medycznych; 28: 7, 451-457.

Knight J, Nigam Y (2017) Diabetes management 1: disease types, symptoms and diagnosis. Nursing Times; 113: 4, 40-44.

Ko GT et al (2006) Effects of age on plasma glucose levels in non-diabetic Hong Kong Chinese. Croatian Medical Journal; 47: 5, 709-713.

Liamis G et al (2008) A review of drug-induced hyponatremia. American Journal of Kidney Disease; 52: 1, 144-153.

Miller M (2009) Fluid balance disorders in the elderly. American Society of Nephrology online curricula: geriatric nephrology.

Peeters RP (2008) Thyroid hormones and aging. Hormones; 7: 1, 28-35.

Portale AA et al (1997) Aging alters calcium regulation of serum concentration of parathyroid hormone in healthy men. American Journal of Physiology; 272: 139-146.

Seals DR, Esler MD (2000) Human ageing and the sympathoadrenal system. Journal of Physiology; 528: 3, 407-417.

Shamonki IM et al (1980) Age-related changes of calcitonin secretion in females. Journal of Clinical Endocrinology and Metabolism; 50: 3, 437-439.

Tiegs RD et al (1986) Secretion and metabolism of monomeric human calcitonin: effects of age, sex, and thyroid damage. Journal of Bone and Mineral Research; 4: 339-349.

Veldhuis JD et al (2005) Joint mechanisms of impaired growth-hormone pulse renewal in aging men. Journal of Clinical Endocrinology and Metabolism; 9: 7, 4177-4183.

Wade AG et al (2007) Efficacy of prolonged release melatonin in insomnia patients aged 55-80 years: quality of sleep and next-day alertness outcomes. Current Medical Research and Opinion; 23: 10, 2597-2605.

Wolf OT (2015) Effects of Stress on Memory: Relevance for Human Aging. Encyclopedia of Geropsychology. Singapore: Springer Science.

Wolf OT et al (2005) Subjective memory complaints in aging are associated with elevated cortisol levels. Neurobiology of Aging; 26: 10, 1357-1363.

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Anatomy and physiology of ageing 7: the endocrine system - Nursing Times