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Life at the Extremes
The debut of a female Steve Jones – likeable, literate, lucid and laconic. A sprightly, lavishly illustrated book on the science of human survival.
How do people survive extremes of heat, cold, depth, speed and altitude? This book explores the limits of human survival and the physiological adaptations which enable us to exist under extreme conditions. In man’s battle for survival in the harshest of environments, the knowledge imparted by physiology, the ‘logic of life’, is crucial. What causes mountain sickness? Why is it possible to reach the top of Everest without supplementary oxygen, yet be killed if a plane depressurises suddenly at the same altitude. Why are astronauts unable to stand without fainting when they return to Earth? Why do human divers get the bends but sperm whales don’t? Will men always be able to run faster than women? Why don’t penguins get frostbite?
How do people survive extremes of heat, cold, depth, speed and altitude? This book explores the limits of human survival and the physiological adaptations which enable us to exist under extreme conditions. In man’s battle for survival in the harshest of environments, the knowledge imparted by physiology, the ‘logic of life’, is crucial. What causes mountain sickness? Why is it possible to reach the top of Everest without supplementary oxygen, yet be killed if a plane depressurises suddenly at the same altitude. Why are astronauts unable to stand without fainting when they return to Earth? Why do human divers get the bends but sperm whales don’t? Will men always be able to run faster than women? Why don’t penguins get frostbite?
354 pages, Kindle Edition
First published July 3, 2000
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About the author
Frances Ashcroft
6 books25 followersFrances Ashcroft MA PhD FRS is a British physiologist. She is Royal Society GlaxoSmithKline Research Professor in the University of Oxford. She is a fellow of Trinity College and, with Kay Davies and Peter Donnelly is a director of the Oxford Centre for Gene Function.
Her research group has an international reputation for work on insulin secretion, type II diabetes and neonatal diabetes. Her work with Professor Andrew Hattersley has helped enable children born with diabetes to switch from insulin injections to tablet therapy.
She is the author of the book Life at the Extremes: The Science of Survival.
Her research group has an international reputation for work on insulin secretion, type II diabetes and neonatal diabetes. Her work with Professor Andrew Hattersley has helped enable children born with diabetes to switch from insulin injections to tablet therapy.
She is the author of the book Life at the Extremes: The Science of Survival.
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May 23, 2022
Labai faina ir tiršta informacijos knyga, tiesiog kaip puslapis – taip įdomybė. Visų jų nė nemėginčiau sutalpinti į apžvalgą, bet papasakosiu kelias, labiau įstrigusias.
Lipant ar skrendant į viršų problema – per žemas slėgis. O problema todėl, kad deguonis nepatenka į plaučius bei kūno audinius, t.y. viršum jo esantis oras tiesiog nesustumia deguonies plaučiuosna, maža to, mūsų organizmas savaime gamina vandens garų, kurie užima deguonies vietą plaučių alveolėse. Trūkstant deguonies, kūnas po biškį atjunginėja savo dalis: nebegali pajudinti galūnių (raumenys naudoja daug deguonies ir labai neefektyviai – daug energijos išeina šilumos pavidalu, dėl to būna šilta pasimankštinus), paskui pradedi haliucionuoti, kartais ištinka net euforija – pavyzdžiui, tokie trys prancūzai kilo oro balionu, ir sutarė, kad naudos deguonies balionus tik kai jau visai nebegalės, kas buvo prasta mintis, nes nuo deguonies trūkumo visi jautėsi labai gerai ir drąsiai, o paskui prarado sąmonę. Vienas kažkaip atsipaipaliojo ir nuleido balioną, bet kiti numirė. Ir, taip – dėl to lėktuve ir iškrenta tos deguonies kaukės, kai sutrinka slėgis salone. Jei keleiviai sėdės ramiai ir nesimakaluos, tai nepraras sąmonės, kol pilotas nutupdys lėktuvą. Sykį – sako autorė – vienam lėktuve sugedo slėgis salone ir pilotas jau ketino užsidėti deguonies kaukę, bet prieš tai pasilenkė pakelti nukritusių akinių, ir prarado sąmonę. Gerai, kad kitas pilotas buvo protingesnis, užsidėjo deguonies kaukę ir saugiai nutupdė lėktuvą.
Nardant atsiranda daug problemų, iš kurių gal akivaizdžiausia – nėra oro. Tačiau ją galima apeiti pumpuojant orą: sistemą tam atrado du broliai, kai užsidegė jų tvartas: vienas užsidėjo senovinį šalmą, prijungė prie jo žarną, o kitas pumpavo orą į tą žarną. Aišku, jei esi po vandeniu, reikia pumpuoti daugiau, nes slėgis didesnis ir atitinkamai sumažėja dujų tūris. Ankstyviesiems narams teko tai gana nemaloniai patirti savo kailiu – jei oro tiekimas sutrikdavo, vanduo tiesiog sustumdavo naro kūną į jo šalmą ir prie jo prijungtą vamzdį (palieku įsivaizduoti jums).
Slėgis sukelia ir kitą pavojingą problemą, kuri išryškėja tik išneriant: esant aukštesniam slėgiui, skysčiuose (šiuo atveju, kraujyje) lengviau ištirpsta dujos (pavyzdžiui, azotas, sudarantis didžiąją dalį mūsų kvėpuojamo oro). Išnėrinėjant su tuo kraujyje ištirpusiu azotu nutinka tas pats, kas su anglies dioksidu gazuotuose gėrimuose: susiformuoja burbuliukai, kas sukelia skausmus sąnariuose, trukdo įkvėpti (jei plaučiuose), o jei smegenyse, tai gali išvis numirti. Dėl to narai naudoja tą pačią techniką, kaip ir mes, jei nenorime, kad mus apipurkštų atsukinėjamas buteliukas – iškilinėja labai lėtai ir etapais.
Dar vienas juokingas, bet paprastas efektas: kai stovi ant žemės, dėl gravitacijos daugiau kraujo kaupiasi kojose, bet jei panyri į vandenį, vandens slėgis veikia kaip priešinga gravitacijai jėga ir pastumia tavo kraują aukštyn krūtinės link, dėl to širdis ima plakti greičiau, išsiplečia prieširdis, o nuo to išsiskiria du hormonai, paskatinantys inkstus apdoroti daugiau vandens – tai štai dėl to panirę į vandenį užsimanome sisioti, hehe.
Žuvys turi plaukimo pūslę, kuri palaiko žuvies plūdrumą, bet tik tam tikroj zonoj – jei pūslė pernelyg susitraukia, žuvis gali nuskęsti:( Rykliai tokios pūslės neturi, tai privalo visada judėti, kad nenuskęstų (panašiai kaip lėktuvai privalo judėti, kad nenukristų).
O kaipgi paukščiai? Jie gi aukštai ir ilgai skraido, kodėl jų nekankina deguonies trūkumas, kurį minėjau pradžioje? Aplink jų plaučius, pasirodo, yra du maišai orui. Įkvepiant prisipildo priekinis, o iškvepiant tas oras per jėgą stumiamas per plaučius – tokias groteles – ir atsiduria galiniame maiše, kol pirmas maišas jau pildosi naujai įkvepiamo oro. Taip sparčiau vyksta oro apykaita ir deguonis agresyviau stumiamas į plaučius (ne taip, kaip pas mus, kur tiesiog reikia laukti, kol jis savaime prasiskverbs)
Panašią sistemą, tik kitu tikslu, turi gazelės – jos gyvena karštose vietose, be to, turi daug bėgioti, kas sugeneruoja daug karščio. Dėl to gazelės nusprendė vėsinti tik smegenis: aplink jų nosį yra kraujagyslių tinklas, kur įkvepiamas oras vėsina TIK į smegenis patenkantį kraują. Šitaip gazelės, net ir perkaitusios visu kūnu, išlaiko šaltą galvą, o kūną vėliau, naktį, atsivėsina.
Bet juk šiluma kaulų nelaužo, tai kur čia problema? Pasirodo, žmonės (ir kiti žinduoliai) gali toleruoti didelį šaltį, o va karščio ne: jei žmogaus kūno vidaus temperatūra pakyla iki 42˚, numiršti. Va taip, tiesiog – sutrūkinėja, t.y. “iškepa” svarbūs baltymai. Ypač jautrios karščiui yra smegenys ir sėklidės – dėl to jos ir tabaluoja išorėje (sėklidės, ne smegenys), ten labiau pasivėsina.
O kaipgi pirtis? – klausiate jūs ir esate teisūs – žmonės gali toleruoti daug aukštesnę temperatūrą, bet tik jei oras labai sausas. Toks ponas Bladgenas sykį nuėjo į užkaitintą iki 105˚ laipsnių, bet labai sauso oro kambarį, nešdamasis kiaušinių bei kumpio ir vedinas šunimi. Po penkiolikos minučių kiaušiniai buvo išvirę, kupis iškepęs, o ponas ir šuo – sveiki (tiesa, šunį patalpino į krepšį, nes jam kaito loputės).
Žmonės vėsinasi gana paprastai – prakaituoja, nes vandens virtimas į garus suvalgo daug karščio (taip pat, kaip puode verdant vandenį). Norint daug išprakaituoti, geriau turėti kuo didesnį kūno paviršių, ilgas plonas rankas ir kojas, pvz kaip kupranugaris. Tačiau kupranugariui dykumoje iškyla kita problema – kur savo kūne turėti maisto sandėliuką? Išskirstyti riebalus po visą kūną negerai, nes riebalų sluoksnis trukdo vėsintis, todėl geriausia viską saugoti vienoje vietoje – kuproje. Žmonės irgi turi tokią kuprą, o vadinasi ji užpakalis.
Kai kurie gyvūnai susirėdė priešingai: jie turi vieną kūno dalį, per kurią vėsinasi. Pavyzdžiui, dramblys turi ausis, o kai kurie paukščiai – ilgas kojas. Kartais jie tas kojas dar ir apsimyža, taip pasidarydami dar vieną vandens (na, skysčio) sluoksnį, kurį garinant naudotųsi kūno šiluma.
Manau, nereikia daug įrodinėti, kad šaltis žmogui irgi gali pakenkti – ir kad galima nuo jo iki kažkokio laipsnio apsisaugoti. Autorė pasakoja apie savo senelį, kuris sužeistas I pasauliniam kare (pašautas į koją, žaizdoj išplito infekcija, prasidėjo uždegimas) buvo gabenamas laivu namo, karščiuojantis prirštas prie gulto. Lyg to būtų negana, laivas buvo pašautas ir nuskendo, o senelis su visu gultu liko plūduriuoti vandenyje. Po daugelio valandų jį visgi išgelbėjo ir senelis išgyveno, kitaip negu daug visiškai sveikų laivo keleivių. KAIP?? Prie to prisidėjo keli veiksniai, sako autorė: pirma, jis buvo pririštas prie gulto ir negalėjo judėti (taigi prarado mažiau šilumos per konvekciją – vandens sluoksnis prie jo kūno mažiau keitėsi), antra, ant kūno turėjo nemažai nuo šalčio saugančių riebalų, o trečia – karštinė gamino jo kūne daugiau šilumos.
Kai šalta, nervai ima prasčiau perdavinėti impulsus į smegenis, dėl to šaltą dieną sunku sugraibyti raktą ar palto sagas. Krentant temperatūrai, odos kraujagyslės susitraukia, kad nešvaistytų šilumos. Paskui, bijodamos, kad negaudami deguonies nugangrenuos pirštai, vėl išsiplečia, paskui vėl susitraukia. Dėl to jūreivių nosys raudonos, nebūtinai nuo girtavimo! Gyvūnai, aišku, vėl turi visokių fainų adaptacijų, pvz žiemojančios varlės pačios gaminasi antifrizą, neleidžiantį kraujui užšalti. Naktiniai drugiai vibruoja sparnais, kad raumenų veikla prigamintų šilumos. Bitės irgi vibruoja savo raumenis, bet taip subtiliai, kad nesimato.
Toliau pasakojama apie sportininkų ribas, bet gal kitąsyk parašysiu, o gal ir ne!
Nesušalkit, neiškepkit ir nesusislėkit!
Lipant ar skrendant į viršų problema – per žemas slėgis. O problema todėl, kad deguonis nepatenka į plaučius bei kūno audinius, t.y. viršum jo esantis oras tiesiog nesustumia deguonies plaučiuosna, maža to, mūsų organizmas savaime gamina vandens garų, kurie užima deguonies vietą plaučių alveolėse. Trūkstant deguonies, kūnas po biškį atjunginėja savo dalis: nebegali pajudinti galūnių (raumenys naudoja daug deguonies ir labai neefektyviai – daug energijos išeina šilumos pavidalu, dėl to būna šilta pasimankštinus), paskui pradedi haliucionuoti, kartais ištinka net euforija – pavyzdžiui, tokie trys prancūzai kilo oro balionu, ir sutarė, kad naudos deguonies balionus tik kai jau visai nebegalės, kas buvo prasta mintis, nes nuo deguonies trūkumo visi jautėsi labai gerai ir drąsiai, o paskui prarado sąmonę. Vienas kažkaip atsipaipaliojo ir nuleido balioną, bet kiti numirė. Ir, taip – dėl to lėktuve ir iškrenta tos deguonies kaukės, kai sutrinka slėgis salone. Jei keleiviai sėdės ramiai ir nesimakaluos, tai nepraras sąmonės, kol pilotas nutupdys lėktuvą. Sykį – sako autorė – vienam lėktuve sugedo slėgis salone ir pilotas jau ketino užsidėti deguonies kaukę, bet prieš tai pasilenkė pakelti nukritusių akinių, ir prarado sąmonę. Gerai, kad kitas pilotas buvo protingesnis, užsidėjo deguonies kaukę ir saugiai nutupdė lėktuvą.
Nardant atsiranda daug problemų, iš kurių gal akivaizdžiausia – nėra oro. Tačiau ją galima apeiti pumpuojant orą: sistemą tam atrado du broliai, kai užsidegė jų tvartas: vienas užsidėjo senovinį šalmą, prijungė prie jo žarną, o kitas pumpavo orą į tą žarną. Aišku, jei esi po vandeniu, reikia pumpuoti daugiau, nes slėgis didesnis ir atitinkamai sumažėja dujų tūris. Ankstyviesiems narams teko tai gana nemaloniai patirti savo kailiu – jei oro tiekimas sutrikdavo, vanduo tiesiog sustumdavo naro kūną į jo šalmą ir prie jo prijungtą vamzdį (palieku įsivaizduoti jums).
Slėgis sukelia ir kitą pavojingą problemą, kuri išryškėja tik išneriant: esant aukštesniam slėgiui, skysčiuose (šiuo atveju, kraujyje) lengviau ištirpsta dujos (pavyzdžiui, azotas, sudarantis didžiąją dalį mūsų kvėpuojamo oro). Išnėrinėjant su tuo kraujyje ištirpusiu azotu nutinka tas pats, kas su anglies dioksidu gazuotuose gėrimuose: susiformuoja burbuliukai, kas sukelia skausmus sąnariuose, trukdo įkvėpti (jei plaučiuose), o jei smegenyse, tai gali išvis numirti. Dėl to narai naudoja tą pačią techniką, kaip ir mes, jei nenorime, kad mus apipurkštų atsukinėjamas buteliukas – iškilinėja labai lėtai ir etapais.
Dar vienas juokingas, bet paprastas efektas: kai stovi ant žemės, dėl gravitacijos daugiau kraujo kaupiasi kojose, bet jei panyri į vandenį, vandens slėgis veikia kaip priešinga gravitacijai jėga ir pastumia tavo kraują aukštyn krūtinės link, dėl to širdis ima plakti greičiau, išsiplečia prieširdis, o nuo to išsiskiria du hormonai, paskatinantys inkstus apdoroti daugiau vandens – tai štai dėl to panirę į vandenį užsimanome sisioti, hehe.
Žuvys turi plaukimo pūslę, kuri palaiko žuvies plūdrumą, bet tik tam tikroj zonoj – jei pūslė pernelyg susitraukia, žuvis gali nuskęsti:( Rykliai tokios pūslės neturi, tai privalo visada judėti, kad nenuskęstų (panašiai kaip lėktuvai privalo judėti, kad nenukristų).
O kaipgi paukščiai? Jie gi aukštai ir ilgai skraido, kodėl jų nekankina deguonies trūkumas, kurį minėjau pradžioje? Aplink jų plaučius, pasirodo, yra du maišai orui. Įkvepiant prisipildo priekinis, o iškvepiant tas oras per jėgą stumiamas per plaučius – tokias groteles – ir atsiduria galiniame maiše, kol pirmas maišas jau pildosi naujai įkvepiamo oro. Taip sparčiau vyksta oro apykaita ir deguonis agresyviau stumiamas į plaučius (ne taip, kaip pas mus, kur tiesiog reikia laukti, kol jis savaime prasiskverbs)
Panašią sistemą, tik kitu tikslu, turi gazelės – jos gyvena karštose vietose, be to, turi daug bėgioti, kas sugeneruoja daug karščio. Dėl to gazelės nusprendė vėsinti tik smegenis: aplink jų nosį yra kraujagyslių tinklas, kur įkvepiamas oras vėsina TIK į smegenis patenkantį kraują. Šitaip gazelės, net ir perkaitusios visu kūnu, išlaiko šaltą galvą, o kūną vėliau, naktį, atsivėsina.
Bet juk šiluma kaulų nelaužo, tai kur čia problema? Pasirodo, žmonės (ir kiti žinduoliai) gali toleruoti didelį šaltį, o va karščio ne: jei žmogaus kūno vidaus temperatūra pakyla iki 42˚, numiršti. Va taip, tiesiog – sutrūkinėja, t.y. “iškepa” svarbūs baltymai. Ypač jautrios karščiui yra smegenys ir sėklidės – dėl to jos ir tabaluoja išorėje (sėklidės, ne smegenys), ten labiau pasivėsina.
O kaipgi pirtis? – klausiate jūs ir esate teisūs – žmonės gali toleruoti daug aukštesnę temperatūrą, bet tik jei oras labai sausas. Toks ponas Bladgenas sykį nuėjo į užkaitintą iki 105˚ laipsnių, bet labai sauso oro kambarį, nešdamasis kiaušinių bei kumpio ir vedinas šunimi. Po penkiolikos minučių kiaušiniai buvo išvirę, kupis iškepęs, o ponas ir šuo – sveiki (tiesa, šunį patalpino į krepšį, nes jam kaito loputės).
Žmonės vėsinasi gana paprastai – prakaituoja, nes vandens virtimas į garus suvalgo daug karščio (taip pat, kaip puode verdant vandenį). Norint daug išprakaituoti, geriau turėti kuo didesnį kūno paviršių, ilgas plonas rankas ir kojas, pvz kaip kupranugaris. Tačiau kupranugariui dykumoje iškyla kita problema – kur savo kūne turėti maisto sandėliuką? Išskirstyti riebalus po visą kūną negerai, nes riebalų sluoksnis trukdo vėsintis, todėl geriausia viską saugoti vienoje vietoje – kuproje. Žmonės irgi turi tokią kuprą, o vadinasi ji užpakalis.
Kai kurie gyvūnai susirėdė priešingai: jie turi vieną kūno dalį, per kurią vėsinasi. Pavyzdžiui, dramblys turi ausis, o kai kurie paukščiai – ilgas kojas. Kartais jie tas kojas dar ir apsimyža, taip pasidarydami dar vieną vandens (na, skysčio) sluoksnį, kurį garinant naudotųsi kūno šiluma.
Manau, nereikia daug įrodinėti, kad šaltis žmogui irgi gali pakenkti – ir kad galima nuo jo iki kažkokio laipsnio apsisaugoti. Autorė pasakoja apie savo senelį, kuris sužeistas I pasauliniam kare (pašautas į koją, žaizdoj išplito infekcija, prasidėjo uždegimas) buvo gabenamas laivu namo, karščiuojantis prirštas prie gulto. Lyg to būtų negana, laivas buvo pašautas ir nuskendo, o senelis su visu gultu liko plūduriuoti vandenyje. Po daugelio valandų jį visgi išgelbėjo ir senelis išgyveno, kitaip negu daug visiškai sveikų laivo keleivių. KAIP?? Prie to prisidėjo keli veiksniai, sako autorė: pirma, jis buvo pririštas prie gulto ir negalėjo judėti (taigi prarado mažiau šilumos per konvekciją – vandens sluoksnis prie jo kūno mažiau keitėsi), antra, ant kūno turėjo nemažai nuo šalčio saugančių riebalų, o trečia – karštinė gamino jo kūne daugiau šilumos.
Kai šalta, nervai ima prasčiau perdavinėti impulsus į smegenis, dėl to šaltą dieną sunku sugraibyti raktą ar palto sagas. Krentant temperatūrai, odos kraujagyslės susitraukia, kad nešvaistytų šilumos. Paskui, bijodamos, kad negaudami deguonies nugangrenuos pirštai, vėl išsiplečia, paskui vėl susitraukia. Dėl to jūreivių nosys raudonos, nebūtinai nuo girtavimo! Gyvūnai, aišku, vėl turi visokių fainų adaptacijų, pvz žiemojančios varlės pačios gaminasi antifrizą, neleidžiantį kraujui užšalti. Naktiniai drugiai vibruoja sparnais, kad raumenų veikla prigamintų šilumos. Bitės irgi vibruoja savo raumenis, bet taip subtiliai, kad nesimato.
Toliau pasakojama apie sportininkų ribas, bet gal kitąsyk parašysiu, o gal ir ne!
Nesušalkit, neiškepkit ir nesusislėkit!
September 16, 2020
I've found 1st year physiology to be a really fun subject, mostly because, unlike most of the other subjects we've covered thus far, you can really think through a lot of the concepts to completion, without ridiculous amounts of rote learning.
This book essentially takes a lot of those concepts and applies them to some of the stresses a human being might experience - climbing at high altitudes, diving, dealing with high and low temperatures, and lastly, being in space. The stuff on altitude and pressure at depth was all quite intuitive, together with the discussion on thermoregulation - a nice summary of the physiology I learnt through lectures I suppose!
However, it was in the chapter on space where a lot of links really came together. The control of blood pressure is extremely complex. Without going into excessive detail, it is a homeostatic system that is altered significantly when in orbit. The heart adapts to a reduced return of blood to it from the veins in the legs (because the muscles in the legs are contracting less to propel the blood back to the heart), shrinking in size and reducing its maximal output. This isn't a big issue in space, but creates a lot of problems upon a return to Earth. Some of us may have experienced a slight sensation of almost blacking out after standing up, having sat down for too long. Astronauts experience a far more severe version of this upon their return to Earth - orthostatic intolerance.
The key issue is that when we stand up, blood that has pooled in our legs has a harder time returning to the heart (consider how the return is vertical now, rather than horizontal), so this reduces the return of blood to the heart. This produces an acute reduction in the cardiac output, which the blood pressure receptors usually detect very quickly, responding by increasing the cardiac output by increasing the heart rate. However, astronauts, because of their time in space, have diminished cardiac muscle mass, and cannot respond to their blood pressure receptors signals to increase the heart rate as effectively. As a result, they apparently end up fainting upon standing up quite frequently in their first few days back on Earth!
Most of the book is dedicated to the intricacies of the responses of the human body to acute or prolonged physiological stresses, but at the end, it deals with permanent adaptations displayed by some species. It is one thing to have compensation of some kind that allows some physiological reprieve when stuck in extreme cold or heat; archaea and some bacteria have the capacity to grow and thrive in such environments. A good example raised was the evocatively named baccillus infernus - the "bacteria from hell" which dwells deep within the Earth's core, at pressures close to 600 atmospheres, and temperatures approaching 1000 degrees celsius.
The reverse would be organisms that survive in the extreme cold. The most immediate problem this presents is the freezing of water, the main solvent for the cells of most (if not all) organisms. For smaller, single celled organisms, this sounds feasible on paper, because biological antifreezes like glycerol can help to stop water freezing, and forming crystals that might puncture their cell membranes. The real challenge is faced by multicellular organisms, like the Siberian salamander, which essentially goes into cyrostasis during the long winter, shutting down nearly all metabolic processes. It eventually "thaws out" for the summer, to reproduce and gather the nutrients it needs to survive the next winter.
Overall, I really enjoyed this book, it was a nice way to relax, while simultaneously revising some physiology before my exam!
This book essentially takes a lot of those concepts and applies them to some of the stresses a human being might experience - climbing at high altitudes, diving, dealing with high and low temperatures, and lastly, being in space. The stuff on altitude and pressure at depth was all quite intuitive, together with the discussion on thermoregulation - a nice summary of the physiology I learnt through lectures I suppose!
However, it was in the chapter on space where a lot of links really came together. The control of blood pressure is extremely complex. Without going into excessive detail, it is a homeostatic system that is altered significantly when in orbit. The heart adapts to a reduced return of blood to it from the veins in the legs (because the muscles in the legs are contracting less to propel the blood back to the heart), shrinking in size and reducing its maximal output. This isn't a big issue in space, but creates a lot of problems upon a return to Earth. Some of us may have experienced a slight sensation of almost blacking out after standing up, having sat down for too long. Astronauts experience a far more severe version of this upon their return to Earth - orthostatic intolerance.
The key issue is that when we stand up, blood that has pooled in our legs has a harder time returning to the heart (consider how the return is vertical now, rather than horizontal), so this reduces the return of blood to the heart. This produces an acute reduction in the cardiac output, which the blood pressure receptors usually detect very quickly, responding by increasing the cardiac output by increasing the heart rate. However, astronauts, because of their time in space, have diminished cardiac muscle mass, and cannot respond to their blood pressure receptors signals to increase the heart rate as effectively. As a result, they apparently end up fainting upon standing up quite frequently in their first few days back on Earth!
Most of the book is dedicated to the intricacies of the responses of the human body to acute or prolonged physiological stresses, but at the end, it deals with permanent adaptations displayed by some species. It is one thing to have compensation of some kind that allows some physiological reprieve when stuck in extreme cold or heat; archaea and some bacteria have the capacity to grow and thrive in such environments. A good example raised was the evocatively named baccillus infernus - the "bacteria from hell" which dwells deep within the Earth's core, at pressures close to 600 atmospheres, and temperatures approaching 1000 degrees celsius.
The reverse would be organisms that survive in the extreme cold. The most immediate problem this presents is the freezing of water, the main solvent for the cells of most (if not all) organisms. For smaller, single celled organisms, this sounds feasible on paper, because biological antifreezes like glycerol can help to stop water freezing, and forming crystals that might puncture their cell membranes. The real challenge is faced by multicellular organisms, like the Siberian salamander, which essentially goes into cyrostasis during the long winter, shutting down nearly all metabolic processes. It eventually "thaws out" for the summer, to reproduce and gather the nutrients it needs to survive the next winter.
Overall, I really enjoyed this book, it was a nice way to relax, while simultaneously revising some physiology before my exam!
February 18, 2013
As a Christmas present to myself, I decided to read Life at the Extremes: The Science of Survival by Frances Ashcroft, professor of physiology at the University of Oxford. And what a Christmas present it was! This book was a hidden gem in the library.
Life at the Extremes is all about the effects of the extreme environmental conditions on the human body, including heat and cold, height and depths, space, microgravity and, with regards to sport, pushing your body to the limit.
Highly accessible and filled with science, this book is perfect for anyone, but I would especially recommend this to A Level Biology students like me or those who want to do Biology or Medicine at university. The book covers so many aspects of physiology that we experience almost daily in our lives like how we regulate heat and cold, the energy demands of speed and stamina, and aspects that we do not, such as living in microgravity and high altitude, etc.
The book is divided into 7 sections: Life at the Top, Life under Pressure, Life in the Hot Zone, Life in the Cold, Life in the Fast Lane, The Final Frontier and The Outer Limits.
Life at the Top talks about the high life - literally. It talks about altitude sickness and why it occurs. What I love most about this book, and especially this chapter, is that there is also some history of how these conditions were studied.
Altitude sickness is a condition that usually occurs when you're at a high altitude (usually above 8,000 feet), which occurs when you climb up too quickly without allowing your body to acclimatise to the conditions on top of the mountain.
This occurs because the air pressure at higher altitudes are lower than at sea level. As a result, the amount of oxygen we get into our blood is lowered and the body has to acclimatise. If this acclimatisation process does not occur, the condition can be fatal and there are unpleasant symptoms such as headaches, dizziness, exhaustion and nausea, which take their toll when you're climbing a snow-coated and dangerous mountain like the Everest.
In the chapter, Ashcroft discusses the lungs and the role of haemoglobin in our red blood cells and how this globular protein transports oxygen to our cells. The role of the hormone erythropoetin, the chemical that stimulates the production of red blood cells, is also discussed and it is interesting to note that some athletes used this hormone to improve their performance by using it to increase their red blood cell levels, and it is even more interesting to note that it is probably of little benefit!
The next chapter, Life under Pressure, is about how humans cope in the depths of the oceans. There is definitely a lot more science in this chapter, especially the physics of pressure, which can sometimes be difficult to keep up with, however, all is explained clearly. History about the development of the diving suit is recounted and how the first cases of the bends came about.
The bends, or decompression sickness, occurs when a diver who has been at depths of over 10m under water for a long period of time rises quickly. This happens because a lot of nitrogen dissolves into the blood under pressure. When the diver rises quickly, the pressure is suddenly lowered and so the nitrogen can no longer stay dissolved into the blood and so it comes out of the solution to form gas bubbles inside your body and blocks the flow of blood in small blood vessels, resulting in joint pain and paralysis, especially when the blood vessels to the brain are blocked. The phenomenon is similar to the fizzing of a fizzy drink like coca-cola when you open a can. Carbon dioxide dissolved under high pressure suddenly comes out of the solution as the pressure drops. The condition can be fatal due to the lack of oxygen and nutrients provided to the cells and tissues when blood vessels are blocked.
The biology in the chapter is incredible fascinating. Ashcroft also explains that whales don't get the bends because they limit the gas dissolving into their blood by breathing out before a dive, and limiting blood flow to the lungs.
Chapter three, Life in the Hot Zone, discusses how heat affects the human body and how we sense heat. There is also plentiful history about the development of the thermometer. Ashcroft talks about how and why we regulate our bodies: homoeostasis, the processes that occur in the body to keep our body functioning normally.. Homeostasis is important to keep our body functioning properly, and this involves regulating the temperature so that the core body temperature reaches the "just right" temperature, which is important as our metabolism depends on enzymes which work best at the "just right," optimum temperature. This is why when it's too cold or too hot, we can die from hypothermia or hyperthermia, because cellular activity is affected hugely.
There is also a lot about physiology in this chapter, especially about the thermoregulatory system and how the skin disperses body heat into the atmosphere, but the chapter reads well because it is in the form of stories and analogies so it doesn't sound like a textbook. As a result, it is so easy to become engrossed in this book.
Life in the Cold is about... life in the cold! Frostbite, hypothermia and related conditions are explained in this chapter. Other animals are also discussed, indeed a large part of this section talks about how different animals are adapted to coldness, penguins especially.
I think it is amazing how Emperor penguins can coordinate themselves to be in a large group to conserve heat and huddle for warmth, facing continuous darkness and temperatures below -70 degrees Celsius. Incredible! It is also amazing that babies are born with "brown fat," or brown adipose tissue, which have a greater number of ATP-producing, energy-providing mitochondria. Mitochondria produce ATP which can provide energy to burn the fat and act as a heater for babies so that they do not suffer from hypothermia. Babies have this brown fat because of their larger surface area to volume ratio, which means that their rate of heat loss is much quicker than in adults.
ATP is discussed in more detail in Life in the Fast Lane, the chapter about pushing the human body to the limits of speed, strength and stamina. So much information is provided but it is beneficial most especially for A Level Biology students!
I think this is the most interesting section of the book. Ashcroft describes how muscle contraction occurs, from the triggering by calcium ions, to how glycogen stores are depleting, turning them into glucose, which is used to make ATP, to the protein filaments interlocking and breaking bonds and reforming them. Incredible.
The chapter also discusses the difference between men and women's physique, and how it contributes to being better in a certain sport. For example, women tend to have a greater fat percentage than men do, so women are often better in long distance swimming where buoyancy is important, and men are better in sprinting where as little a ratio of fat to muscle mass is required. The chapter ends with the thought that although moderate exercise can slow bone loss in older women.
The next chapter, The Final Frontier, truly appealed to my inner space nerd. It is so enthralling to hear about astronauts in outer space taking that giant leap for mankind, but it is even more engrossing to hear the stories in relation to the effects of microgravity in space. Space is the ultimate frontier - the ultimate extreme. It is a vacuum. It is freezing but the ultraviolet rays from the sun would burn your skin. To get there, you must be accelerated to over 25,056 miles per hour, subjecting you to extreme g-forces and when you're there, you exist in microgravity. As a result, many physiological changes occur such as a shift in body fluids.
Usually, fluid accumulated in the lower half of the body due to gravity; in microgravity, body fluids migrate to the chest and head and redistribute again, causing the moon-face appearance of some astronauts. The heart does not pump as hard due to not having to pump against gravity.
Equilibrioception (the sense of balance) can also be damaged. Dizziness can occur due to Space Adaptation Syndrome, a condition suffered by astronauts in orbit when the state of weightlessness stops their vestibular system from working properly. Reduced production of red blood cells, bone loss, muscle wasting - these are all trials and tribulations that greet the brave astronaut in space.
The last chapter, The Outer Limits, although not about human physiology, is also very fascinating. How some microorganisms can grow at 113 degrees Celsius, and others can grow at a pH of 2 is incredible. And even life without oxygen is possible! For certain microorganisms, that is. It seems so bizarre that oxygen, something that we is vital to our survival, is toxic to other organisms.
Ashcroft truly amazes the reader in this chapter. It is very well-researched and has prompted me to do some research myself - it turns out that there are microorganisms that have even adapted to build their DNA using arsenic, which is toxic to humans! Wow. Such is the incredible diversity of life.
I cannot recommend this book enough! It is a delightful read and it bears witness to the human tenacity. Part-survival guide, part-scientific textbook, Life at the Extremes should be in the shelves of every armchair adventurer, explorer, science enthusiast and Biology students.
Life at the Extremes is all about the effects of the extreme environmental conditions on the human body, including heat and cold, height and depths, space, microgravity and, with regards to sport, pushing your body to the limit.
Highly accessible and filled with science, this book is perfect for anyone, but I would especially recommend this to A Level Biology students like me or those who want to do Biology or Medicine at university. The book covers so many aspects of physiology that we experience almost daily in our lives like how we regulate heat and cold, the energy demands of speed and stamina, and aspects that we do not, such as living in microgravity and high altitude, etc.
The book is divided into 7 sections: Life at the Top, Life under Pressure, Life in the Hot Zone, Life in the Cold, Life in the Fast Lane, The Final Frontier and The Outer Limits.
Life at the Top talks about the high life - literally. It talks about altitude sickness and why it occurs. What I love most about this book, and especially this chapter, is that there is also some history of how these conditions were studied.
Altitude sickness is a condition that usually occurs when you're at a high altitude (usually above 8,000 feet), which occurs when you climb up too quickly without allowing your body to acclimatise to the conditions on top of the mountain.
This occurs because the air pressure at higher altitudes are lower than at sea level. As a result, the amount of oxygen we get into our blood is lowered and the body has to acclimatise. If this acclimatisation process does not occur, the condition can be fatal and there are unpleasant symptoms such as headaches, dizziness, exhaustion and nausea, which take their toll when you're climbing a snow-coated and dangerous mountain like the Everest.
In the chapter, Ashcroft discusses the lungs and the role of haemoglobin in our red blood cells and how this globular protein transports oxygen to our cells. The role of the hormone erythropoetin, the chemical that stimulates the production of red blood cells, is also discussed and it is interesting to note that some athletes used this hormone to improve their performance by using it to increase their red blood cell levels, and it is even more interesting to note that it is probably of little benefit!
The next chapter, Life under Pressure, is about how humans cope in the depths of the oceans. There is definitely a lot more science in this chapter, especially the physics of pressure, which can sometimes be difficult to keep up with, however, all is explained clearly. History about the development of the diving suit is recounted and how the first cases of the bends came about.
The bends, or decompression sickness, occurs when a diver who has been at depths of over 10m under water for a long period of time rises quickly. This happens because a lot of nitrogen dissolves into the blood under pressure. When the diver rises quickly, the pressure is suddenly lowered and so the nitrogen can no longer stay dissolved into the blood and so it comes out of the solution to form gas bubbles inside your body and blocks the flow of blood in small blood vessels, resulting in joint pain and paralysis, especially when the blood vessels to the brain are blocked. The phenomenon is similar to the fizzing of a fizzy drink like coca-cola when you open a can. Carbon dioxide dissolved under high pressure suddenly comes out of the solution as the pressure drops. The condition can be fatal due to the lack of oxygen and nutrients provided to the cells and tissues when blood vessels are blocked.
The biology in the chapter is incredible fascinating. Ashcroft also explains that whales don't get the bends because they limit the gas dissolving into their blood by breathing out before a dive, and limiting blood flow to the lungs.
Chapter three, Life in the Hot Zone, discusses how heat affects the human body and how we sense heat. There is also plentiful history about the development of the thermometer. Ashcroft talks about how and why we regulate our bodies: homoeostasis, the processes that occur in the body to keep our body functioning normally.. Homeostasis is important to keep our body functioning properly, and this involves regulating the temperature so that the core body temperature reaches the "just right" temperature, which is important as our metabolism depends on enzymes which work best at the "just right," optimum temperature. This is why when it's too cold or too hot, we can die from hypothermia or hyperthermia, because cellular activity is affected hugely.
There is also a lot about physiology in this chapter, especially about the thermoregulatory system and how the skin disperses body heat into the atmosphere, but the chapter reads well because it is in the form of stories and analogies so it doesn't sound like a textbook. As a result, it is so easy to become engrossed in this book.
Life in the Cold is about... life in the cold! Frostbite, hypothermia and related conditions are explained in this chapter. Other animals are also discussed, indeed a large part of this section talks about how different animals are adapted to coldness, penguins especially.
I think it is amazing how Emperor penguins can coordinate themselves to be in a large group to conserve heat and huddle for warmth, facing continuous darkness and temperatures below -70 degrees Celsius. Incredible! It is also amazing that babies are born with "brown fat," or brown adipose tissue, which have a greater number of ATP-producing, energy-providing mitochondria. Mitochondria produce ATP which can provide energy to burn the fat and act as a heater for babies so that they do not suffer from hypothermia. Babies have this brown fat because of their larger surface area to volume ratio, which means that their rate of heat loss is much quicker than in adults.
ATP is discussed in more detail in Life in the Fast Lane, the chapter about pushing the human body to the limits of speed, strength and stamina. So much information is provided but it is beneficial most especially for A Level Biology students!
I think this is the most interesting section of the book. Ashcroft describes how muscle contraction occurs, from the triggering by calcium ions, to how glycogen stores are depleting, turning them into glucose, which is used to make ATP, to the protein filaments interlocking and breaking bonds and reforming them. Incredible.
The chapter also discusses the difference between men and women's physique, and how it contributes to being better in a certain sport. For example, women tend to have a greater fat percentage than men do, so women are often better in long distance swimming where buoyancy is important, and men are better in sprinting where as little a ratio of fat to muscle mass is required. The chapter ends with the thought that although moderate exercise can slow bone loss in older women.
The next chapter, The Final Frontier, truly appealed to my inner space nerd. It is so enthralling to hear about astronauts in outer space taking that giant leap for mankind, but it is even more engrossing to hear the stories in relation to the effects of microgravity in space. Space is the ultimate frontier - the ultimate extreme. It is a vacuum. It is freezing but the ultraviolet rays from the sun would burn your skin. To get there, you must be accelerated to over 25,056 miles per hour, subjecting you to extreme g-forces and when you're there, you exist in microgravity. As a result, many physiological changes occur such as a shift in body fluids.
Usually, fluid accumulated in the lower half of the body due to gravity; in microgravity, body fluids migrate to the chest and head and redistribute again, causing the moon-face appearance of some astronauts. The heart does not pump as hard due to not having to pump against gravity.
Equilibrioception (the sense of balance) can also be damaged. Dizziness can occur due to Space Adaptation Syndrome, a condition suffered by astronauts in orbit when the state of weightlessness stops their vestibular system from working properly. Reduced production of red blood cells, bone loss, muscle wasting - these are all trials and tribulations that greet the brave astronaut in space.
The last chapter, The Outer Limits, although not about human physiology, is also very fascinating. How some microorganisms can grow at 113 degrees Celsius, and others can grow at a pH of 2 is incredible. And even life without oxygen is possible! For certain microorganisms, that is. It seems so bizarre that oxygen, something that we is vital to our survival, is toxic to other organisms.
Ashcroft truly amazes the reader in this chapter. It is very well-researched and has prompted me to do some research myself - it turns out that there are microorganisms that have even adapted to build their DNA using arsenic, which is toxic to humans! Wow. Such is the incredible diversity of life.
I cannot recommend this book enough! It is a delightful read and it bears witness to the human tenacity. Part-survival guide, part-scientific textbook, Life at the Extremes should be in the shelves of every armchair adventurer, explorer, science enthusiast and Biology students.
January 18, 2020
Amazing book on the human physiology, explicitly describing how the processes in human body are reacting on the extreme conditions, such as high/low pressure and temperature, microgravity and etc . Great examples on the other living organisms not only surviving but actively flourishing at the environment, fatal to the human beings, and what are the natural mechanisms allowing them to do so. Recommended!
Read
June 10, 2017I noticed that people complain about abundance of facts in the book, which otherwise could be easily fetched to you by Google. Yes there are facts, numbers and statistics. And for good reason.
However, these digits and stories of history's firsts don't constitute the bulk of the book, or at least the most interesting and practical part of it. IMHO readers benefit most from detailed explanation of how your body (and those of some other living creatures) reacts to exposure to most extreme conditions at different levels. It is extremely curious and enlightening. A lot of these facts (especially regarding helping the injured) run against the grain of conventional wisdom.
However, these digits and stories of history's firsts don't constitute the bulk of the book, or at least the most interesting and practical part of it. IMHO readers benefit most from detailed explanation of how your body (and those of some other living creatures) reacts to exposure to most extreme conditions at different levels. It is extremely curious and enlightening. A lot of these facts (especially regarding helping the injured) run against the grain of conventional wisdom.
May 21, 2020
İnsan vücudunun sınırlarını zorlayacak kadar hayatı uçlarda yaşayan o küçük azınlığına mensupsanız bu kitabı muhakkak okumalısınız. Ama benim gibi insanlığın geri kalan tembel yığının mutlu bir parçasıysanız da genel kültür açısından okumanız faydalı olabilir. Kitap boyunca yer yer klasik İngiliz espri anlayışına maruz kalınsa da kullanılan dil kolay ve anlaşılır. Baskı kalitesi de ayrıca başarılı.
July 2, 2018
I genuinely feel like I've learnt SO MUCH from reading this book! It reminds me of some of my all-time favourite books that I read as a child - not Malory Towers, but books like 100 Most Dangerous Things on the Planet, Deadly Peril and anything to do with catastrophes. It was a real joy to read Life At The Extremes, just as those aforementioned books were enjoyable, because there were new facts and ideas lurking on every page, and I couldn't help but share my newly discovered information with anyone around me, probably to their dismay.
August 28, 2021
Pretty in-depth review of physiology at extreme environments, at times a bit ardorous & outdated
February 12, 2023
Интересный нонфикшн для того, чтобы фонтанировать фактами на вечеринке)
Эта книга рассказывает об экстремальных условиях, в которых может выжить и выживает человек (и не человек вовсе). Каждая глава посвящена определенному типу условий - водная глубина, полярный холод, горные высоты и тд. И понятным простым (по возможности ) ) языком объясняются реакции нашего организма на такие условия.
Что такое кесонная болезнь? Как можно выжить в парилке под 110 градусов? Почему люди отмораживают пальцы и как это спасает им жизнь? На эти вопросы вы найдете ответы в этой книжке.
Удивительно, на что способен наш организм и как в то же время он хрупок по сравнению с ребятками, которые выдерживают температуры кипения, например.
Как раз про таких экстремалов есть последняя глава, которая мне не зашла, хотелось ее побыстрее пролистать, но в остальном - отличное чтение)
Эта книга рассказывает об экстремальных условиях, в которых может выжить и выживает человек (и не человек вовсе). Каждая глава посвящена определенному типу условий - водная глубина, полярный холод, горные высоты и тд. И понятным простым (по возможности ) ) языком объясняются реакции нашего организма на такие условия.
Что такое кесонная болезнь? Как можно выжить в парилке под 110 градусов? Почему люди отмораживают пальцы и как это спасает им жизнь? На эти вопросы вы найдете ответы в этой книжке.
Удивительно, на что способен наш организм и как в то же время он хрупок по сравнению с ребятками, которые выдерживают температуры кипения, например.
Как раз про таких экстремалов есть последняя глава, которая мне не зашла, хотелось ее побыстрее пролистать, но в остальном - отличное чтение)
April 16, 2013
Fascinating! Scientific findings are interspersed with interesting personal observations making it a fluid read despite being filled to the brim with information. However, although I enjoyed that parallels were drawn and scientific findings illustrated with examples from the author's personal experience, it was clear that unsubstantiated assumptions were being sometimes made. For examples, it was clear that the author only had observed schoolchildren in the UK when he states that "...Raynaud's syndrome (like chilblains) is less common in countries with relatively severe winters, like...Sweden, than in milder countries such as Britain and Italy, perhaps because the harsher climate ensures that people take better precautions. In Britain, for example, schoolchildren play outside in winter and are thus chronically exposed to cold." Although I'm certain that the first theory is correct (in terms of clothing), the deduction that British children play more outside in the winter than Swedish children would make anyone who has been to these countries laugh out loud. After having lived for at least 5 years in each of these three countries, I can confidently say that Swedish schoolchildren spend the most time playing outside in the winter (and Italian children the least). The Swedish saying that "there is no such thing as bad weather, only bad clothing" is known to all Swedish children old enough to go to school.
As could be expected considering that I bought this book more than ten years ago, some of the (sports) nutritional "advice" is somewhat outdated and newer findings and records are obviously not included. Still, I think that almost everyone interested in science will find that this provides an enjoyable, rewarding and fascinating read.
As could be expected considering that I bought this book more than ten years ago, some of the (sports) nutritional "advice" is somewhat outdated and newer findings and records are obviously not included. Still, I think that almost everyone interested in science will find that this provides an enjoyable, rewarding and fascinating read.
October 7, 2007
I just wrote a long review for this book and then it got erased so screw it.
This book is about a bunch of crazy people who did things before warning labels were invented sometimes in the name of science sometimes just in the spirit of extremism. If you want to learn a lot about phsyiological limits how people have pushed them over the years (temperature, pressure, oxygen, physical feats, etc) give it a look. The chapters are pretty independant of one another too which is nice because you can just skip to what interests you.
Okay now where is that f-ing save button.
This book is about a bunch of crazy people who did things before warning labels were invented sometimes in the name of science sometimes just in the spirit of extremism. If you want to learn a lot about phsyiological limits how people have pushed them over the years (temperature, pressure, oxygen, physical feats, etc) give it a look. The chapters are pretty independant of one another too which is nice because you can just skip to what interests you.
Okay now where is that f-ing save button.
January 12, 2017
I very much enjoyed the various topics covered in this book and the way in which they were covered. I wish I would have had a copy when I was a boy since it presents so many interesting ways of dissecting the world around us and beyond. The details may change or be corrected over time, but the thinking framework presented by Ashcroft offers a recipe for lifelong curiosity.
October 3, 2020
First read this book 5 years ago and absolutely loved it. Interesting re-reading now I have a Biomed degree, as so much of the content of this book was revision!! Still quite incredible though.
I'm going to be such a boss at trivia in my old age. So fascinating!
I'm going to be such a boss at trivia in my old age. So fascinating!
February 1, 2022
Anyone interested in the limits of human physiology will find this book fascinating. Technically, its subject matter is broader than that, considering the environmental limits of living creatures, generally. However, all but the last chapter focuses on how humans react to (and adapt to) extreme conditions. Chapters one through six explore the challenges and limitations of humans under extreme conditions of elevation (ch. 1,) of pressure [underwater] (ch. 2,) of heat (ch. 3,) of cold (ch. 4,) of intense physical activity [running-centric, but deals with strength and power as well] (ch. 5,) and in space (ch. 6.) Then, each chapter reflects upon examples of species that are extremely well-adapted to said conditions, and why. (e.g. After learning about how and why humans have to acclimate to survive high elevation treks, one learns about the bar-headed goose, a bird that can go from sea level to flying over Everest – all in the same day.)
The final chapter (ch. 7) is a bit different in that it discusses extremophiles, creatures that can survive in a wide range of conditions (e.g. acidity, temperature, lack of moisture, lack of oxygen, etc.) that would be certain death not only for humans but for any animals. Most of the species discussed are either single-celled creatures or tiny multi-cellular life (e.g. Tardigrades.) With respect to humans, there is a discussion of the limits and present understanding of suspended animation.
This book offers an intriguing look at life at the extremes. While written by a Professor of Physiology, it’s highly readable for a general audience. It mixes narrative examples in with the discussion of physiology to make the material approachable and engaging. I’d highly recommend this book.
The final chapter (ch. 7) is a bit different in that it discusses extremophiles, creatures that can survive in a wide range of conditions (e.g. acidity, temperature, lack of moisture, lack of oxygen, etc.) that would be certain death not only for humans but for any animals. Most of the species discussed are either single-celled creatures or tiny multi-cellular life (e.g. Tardigrades.) With respect to humans, there is a discussion of the limits and present understanding of suspended animation.
This book offers an intriguing look at life at the extremes. While written by a Professor of Physiology, it’s highly readable for a general audience. It mixes narrative examples in with the discussion of physiology to make the material approachable and engaging. I’d highly recommend this book.
December 5, 2020
I decided to read this book because I am interested in physiology and will hopefully be studying it in more depth at university next year.
The book basically describes and explains some of the difficulties encountered by the body's normal homeostatic mechanisms in extreme environments, from the high altitudes and low pressures experienced by mountaineers and fighter pilots to the high pressures and low temperatures of deep sea diving. There are chapters on very hot environments, very cold environments, space, and, my personal favourite, high level sports physiology.
I liked the narrative style. Ashcroft succinctly describes some of the interesting and often dangerous (probably unethical today) experiments and unfortunate accidents that have led to the current physiological interpretations.
This book is very accessible; a reasonable grasp of high school level physical science concepts is needed to understand some of the explanations given. I recommend to any interested in how the body works.
The book basically describes and explains some of the difficulties encountered by the body's normal homeostatic mechanisms in extreme environments, from the high altitudes and low pressures experienced by mountaineers and fighter pilots to the high pressures and low temperatures of deep sea diving. There are chapters on very hot environments, very cold environments, space, and, my personal favourite, high level sports physiology.
I liked the narrative style. Ashcroft succinctly describes some of the interesting and often dangerous (probably unethical today) experiments and unfortunate accidents that have led to the current physiological interpretations.
This book is very accessible; a reasonable grasp of high school level physical science concepts is needed to understand some of the explanations given. I recommend to any interested in how the body works.
November 14, 2021
A cool book for geeks; nicely illustrated with a good list of additional readings. I came across it on a list of suggested readings for pre-Med students. It’s written by a physiologist who describes what happens to the human body at extremes of high altitude, or upon rapid depressurization, in outer space, deep in the ocean, or when exposed to great cold, heat, physical exertion, and so on. How much can our bodies endure, and what causes them to fail? She also discusses how humans function compared with other animals under the same circumstances and explains why these differences exist. It’s an endless stream of the kind of spiffy trivia that the television character Gil Grissom spouts on every episode of Crime Scene Investigation. It’s also interesting (and, presumably, encouraging for physiology students) how many of these phenomena are still unexplained.
December 1, 2025
What a fascinating book! I’m not a scientist by any stretch of the imagination but this book presented science in such a fascinating way that I learned a ton without hardly knowing it. The British flare (written by an Oxford professor) made it extra fun, though more centigrade-Fahrenheit comparisons would have been nice.
The only thing that would have made it better was if it gave God the credit for creating such amazing human bodies and other creatures, and this wild and wonderful extreme world we all live in. There is no conceivable way all of this could have just evolved! 😂
This is now required reading for my kids as they get to high school level (assigning it now to my advanced reader 13yo).
The only thing that would have made it better was if it gave God the credit for creating such amazing human bodies and other creatures, and this wild and wonderful extreme world we all live in. There is no conceivable way all of this could have just evolved! 😂
This is now required reading for my kids as they get to high school level (assigning it now to my advanced reader 13yo).
February 15, 2025
Heavy on the science with nice interjections of personal and anecdotal accounts from the author’s life as well as frequent and informative illustrations.
However, some aspects and information were very outdated but if anything serve as a means to show just how far we’ve come as a species in the 25 years since this was published. I did also find the final chapter focusing on bacteria and other single cell organisms very dull and did take away from my overall enjoyment of the book.
3.5* rounded up to 4*
However, some aspects and information were very outdated but if anything serve as a means to show just how far we’ve come as a species in the 25 years since this was published. I did also find the final chapter focusing on bacteria and other single cell organisms very dull and did take away from my overall enjoyment of the book.
3.5* rounded up to 4*
August 15, 2018
Kitap çok ekstrem koşulları harika bir şekilde özetlemiş. Aynı zamanda dağcılık, dalgıçlık gibi konularda detaylı bir şekilde hangi durumlarda neler yapılmalı ve nasıl yapılmalı olarak ele almış. Çok sade ve yalın bir dili olduğu için hiç sıkılmadan okunabilecek bir kitap.
October 3, 2018
Bazen insana ansiklopedi okuyormus hissi verse de asiri kosullarda insanin sinirlarini detaylica ve kimi zaman hikayelerle bezeyerek anlatan cok degisik bilimsel bir kitap. Ozellikle asiri durumlara ilgi duyanlara guzel bir okuma olur.
August 18, 2020
An absolute pleasure to read, rammed with fun and interesting facts that sometimes challenged my comprehension but never put me off.
This book has given me insight into topics that I have read upon further to broaden my understanding and is a great overview into the extremes of survival.
This book has given me insight into topics that I have read upon further to broaden my understanding and is a great overview into the extremes of survival.
November 25, 2024
Коллекция занимательных фактов о возможностях человеческого организма в экстремальных условиях: высота, глубина, невесомость, скорость. Написано больше популярно, нежели научно, не так подробно и детально, как другая книга Экшкрофт. Ожидания были выше. Но и явного разочарования нет.
October 14, 2017
Informative.
October 27, 2017
Последняя глава показалась лишней и ооочень скучной. Без нее книга отличная
February 12, 2018
I thoroughly enjoyed reading this book. Filled with lots of interesting facts, it did get a bit technical at times, but well worth the effort to read it.
April 26, 2018
A good angle to understand physiology from.
January 1, 2019
İnsanın sınırlarını tanımak için çok güzel ve akıcı bir kitap
April 30, 2019
Excellent book, love all the science and physiology.
August 11, 2019
A neat approach to understanding human physiology.
June 20, 2020
A fascinating book about the extremes that life can exist. Quite technical in parts but I skimmed over those bits. Fascinating insight into the wonder of life on Earth.
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