Physiology History PDF

Physiology Mark Sholdice HS 2220 What is physiology? the study of normal functions of a healthy body from the Greek word physis (nature) often involves reducing functions to smaller processes e.g. nutrition involves alimentation, mastication, swallowing, digestion, absorpt...

Physiology Mark Sholdice HS 2220 What is physiology? the study of normal functions of a healthy body from the Greek word physis (nature) often involves reducing functions to smaller processes e.g. nutrition involves alimentation, mastication, swallowing, digestion, absorption, transportation, growth, repair, and excretion connections to anatomy (study of structure of the body) often, physiological problems cause disfunction (e.g. diabetes) but abnormal physiology does not always cause disease Historical and conceptual themes I mechanism vs. vitalism mechanism: life can be explained by chemical and physical forces (body operates like a machine) e.g. Hobbes, Descartes vitalism: life is governed by forces unique to living things e.g. Georg Ernst Stahl (1659-1734): “animism”  Historical and conceptual themes II teleology vs. empiricism teleology: explanation of phenomena by referring to the ends they serve e.g. Ptolemy’s astronomy: earth is centre of the universe, because earth is home of humanity and humanity is purpose of universe empiricism: explanation of phenomena by referring to information/data collected through observation e.g. Galileo's astronomy: sun is the centre of the solar system, based on observation with telescopes Historical and conceptual themes III speculation and experimentation speculation: use of reason and observation experimentation: scientific method is a relatively new way of conducting science (developed by Francis Bacon [1561- 1626]), but physiological experiments had occurred for thousands of years physiology as a distinct discipline identity of practitioners changes over time: philosopher → anatomist/physician → scientist Ancient ideas for ancient Greeks, the four humours are the basis of physiology black bile, yellow bile, phlegm, and blood humoural/elemental theories also seen in Ayurvedic and traditional Chinese medicine, along with other medical systems around the world Galenic physiology 1) food is consumed, absorbed, and transformed in the liver into blood with natural spirit (pneuma physicon) 2) blood flows away from liver, and throughout body, like water in an irrigation ditch (non- circulating) 3) blood passes through pores in the heart, where vital spirit is added (pneuma zoticon); lungs help cool the heart 4) blood flows outward from left ventricle to all parts of body; brain adds animal spirit (pneuma psychicon) Galenic physiology, continued an open-ended system: blood and air just dissipates at the ends of the veins and arteries led to teleological anatomy: each body part has a specific function (attractive, retentive, alterative, repulsive, or eliminative) evidence of Galen’s dissection work with animals: rete mirabile does not exist in humans Galen’s teleology: "In fact, those who are enslaved to their sects are not merely devoid of all knowledge, but they will not even stop to learn! Instead of listening as they ought, to the reasons why liquid can enter the bladder through the ureters, but is unable to go back the same way... they refuse to learn; they even go so far as to scoff and maintain that the kidneys as well as many other things have been made by nature for no purpose!... If we are not going to grant the kidneys a faculty for attracting this particular quality... we shall discover no other reason. For surely as everyone sees that either the kidneys must attract the urine or the veins propel it." Physiology from antiquity to early modern period after the fall of Western Roman Empire (AD 476), little development of physiology in the West (closely following Galen) some early criticism of Galen in the Islamic world e.g. Ibn al-Nafis (1213-1288) argued blood does not pass through the heart in pores, but from right to left ventricle and then to lungs more criticism of Galen in western Europe during Renaissance e.g. Realdo Colombo (c. 1515-1559) proposed blood flowed from lungs to heart via pulmonary vein; also thought beat signaled heart pushing blood through arteries Harvey and mechanistic explanation William Harvey (1578- 1657) studies in Padua (anatomy teachers familiar with Vesalius) discovers circulation of the blood if blood does not circulate, liver would have to produce 1800 litres of blood per day threat to Galenism heart is a self-adjusting pump that does not need More mechanistic explanations and innovations Harvey’s discoveries part of a larger trend in science toward use of mathematics and measurement Santorio Santorio (1561-1636) invented pendulum machine to count pulse, large thermometer, and metabolic balance chair René Descartes (1596-1650) muscles work according to hydraulic principles argued soul exists independently of body (mind-body dualism) and probably located in pineal gland Descartes’ human clock "A sick man is in truth no less the creation of God than is man in full health... A clock, composed of wheels and counterweights, is no less exactly obeying all the laws of nature when it is badly made and does not mark the time correctly than when it completely fulfills the intention of its maker; so also the human body may be considered as a machine, so built and composed of bones, nerves, muscles, veins, blood, and skin that even if there were no mind in it, it would not cease to move in all the ways it does at present when it is not moved under the direction of the will." – Descartes, Meditations (1641) Iatromechanists and Iatrochemists Iatromechanists (aka Iatrophysicists) defined disease through analogies drawn from physics (e.g. pumps, levers, springs, and pulleys) e.g. Descartes and Harvey Iatrochemists noticed that some bodily processes were similar to chemical phenomena like fermentation, combustion, and decomposition e.g. Paracelsus (c. 1493- 1541) John Mayow (1641–1679) chemist and physiologist who studied living things as units of combustion famous experiments comparing air consumption of candle and mouse Robert Boyle (1627-1691) had proved that air was necessary for combustion, but Mayow showed that only a certain part of the air was used in combustion and respiration Mayow called this spiritus nitro- aereus, which he thought was a chemical compound Positivism I Auguste Comte (1798-1857) French sociologist who formulates “Positivism” main points: evolution of knowledge: theological → metaphysical → positive most positive systems of knowledge are math and astronomy; least are biology and social sciences stop searching for causes and meanings of things positive knowledge comes from observation use quantification to avoid subjectivism establish laws through correlating facts Positivism II impact on physiology: observation and experimentation became more important than speculation and theory debate over vivisection of animals Claude Bernard (1813-1878) develops experimental physiology: observe a phenomenon, localize it in anatomical structure, and then surgically alter structure Experimentation physiology research depended (and still depends) on animal experimentation anti-vivisection movement grew in late 19th and early 20th centuries “Brown Dog Affair” of 1903-1910 in 1906, anti-vivisection activists create memorial in London, UK to memory of dog used in experiments medical students riot several times and try 20th-century advances further development of mechanistic theory e.g. cardiac contraction and circulation is both electrical as well as muscular; respiration involves chemical reactions at cellular and molecular levels hormones and vitamins identified as enzymes of living processes new discoveries in genetics e.g. Murray Barr and the “Barr body” psychology and psychiatry increasingly understood in physiological terms Recent developments physiological research is divided among various specialties e.g. circulatory, respiratory, reproductive, neurological, and digestive systems Western medicine celebrated for scientific discoveries and therapeutic developments, but other areas may be neglected e.g. social, cultural, environmental, and economic determinants of health teleology and vitalism have been rejected in favour of