Principles of Animal Physiology 2/e - Chapter 1

Introduction to Physiological PrinciplesPhysiology“The study of how animals work” Knut Schmidt-Nielsen (1915–2007)Structure and function of various partsHow these parts work together/are integratedDiversity of animalsMore than 1 million species live on EarthUnifying themesApply to all physiological processesHistory of Animal PhysiologyHippocrates (460–circa 377 B.C.)Father of medicineCareful observationAristotle (384–322 B.C.)Father of natural historyRelationship between structure and functionClaudius Galenus, “Galen” (129–circa 199)First experimental physiologistSystematic and carefully designed expts to probe the function of the bodyDetailed descriptions of anatomyDescribed the basis of many physiological processesFounder of PhysiologyHistory of Animal Physiology – cont’dIbn al-Nafis (1213–1288) [Middle Ages]Anatomy of heart and lungsAndreas Vesalius (1514–1564)First modern anatomy textbook De Humani Corporis Fabrica Showed that Galen had made errorsTriggered the modern study of anatomy and physiologyWilliam Harvey (1578–1657)Circulation of blood through the body by contractions of the heart Postulated closed circulationHistory of Animal Physiology – cont’dHerman Boerhaave and Albrecht von Haller (1700s)Bodily functions are a combination of chemical and physical processesPrior to this all physiologists were eitherIatrochemists (body functions involved only chemical reactions)Iatrophysicists (body functions involved only physical processes) laid the foundation for the modern, integrated study of physiology History of Animal Physiology – cont’dMatthias Schleiden and Theodor Schwann (1838)“Cell theory”Claude Bernard (1813–1878)Hb carries O2; liver contains glycogen; ductless glands produce hormones…Milieu interieur (internal environment) Internal environment distinct from external environmentWalter Cannon (1871–1945)“Homeostasis”History of Animal Physiology – cont’dBefore 20th century, little distinction between animal physiology and medical physiologyIn 20th century, became interested in applying the emerging physiological principles to understand diversityPer Scholander (1905–1980)Comparative physiologyC. Ladd Prosser (1907–2002)Central pattern generatorsKnut Schmidt-Nielsen (1915–2007)Animals in harsh and unusual environmentsHistory of Animal Physiology – cont’dGeorge Bartholomew (1923–2006)Ecological physiology‘how an organism interacts with its environment’Peter Hochachka (1937–2002) and George Somero (1941– )Biochemical adaptations‘how molecules make organisms work best in their own specific environments’First to go subcellularPhysiological SubdisciplinesBased on and categorized by:Biological level of organizationProcess that causes physiological variationUltimate goals of the researchMany physiological questions encompass elements from each subdiscipline1. Biological Level of OrganizationCell and molecular physiologyGenetics, metabolism, organellesSystems physiologyFunction of organs/interactionsOrganismal physiologyWhole animalEcological physiologyAnimal and its environmentIntegrative physiologyMultiple levels of organizationBiological Level of Organization – cont’dFigure 1.2Biological Level of OrganizationPhysiologists often study processes at more than one levelReductionism – understand a system by studying the function of its partsEmergence – the whole is more than the sum of its partsPhysiologists are interested in these emergent properties – study interactions2. Process that Causes Physiological VariationDevelopmental physiologyChange as animal growsEnvironmental physiologyChange in response to environmentEvolutionary physiologyChange due to natural selectionEach can be addressed at any of the biological levels of organization3. Ultimate Goals of the ResearchPure physiologyNo specific goal, other than knowledgeApplied physiologyMedical physiologyComparative physiologyOrigins and nature of physiological diversityAugust Krogh principle – “For every biological system there is an organism on which it can be most conveniently studied”Model speciesFeatures conducive to experimentationCan provide insight into how process works in species of intereste.g. squid giant axonUnifying Themes in PhysiologyPhysiological processes obey physical and chemical lawsPhysiological processes are usually regulatedHomeostasis – maintenance of internal constancyPhysiological phenotype is a product of genotype and environmentGenotype – genetic makeupPhenotype – morphology, physiology, and behaviorGenotype is the product of evolutioni. Physics and ChemistryPhysical properties of cells and tissue are linked to structure and function (e.g. bone)Molecular interactions are governed by chemical lawsThermodynamics and kineticsElectrical laws describe membrane function; especially excitable cellsBody size has profound effects on physiological processesAllometric scalingVariables do not change linearly with body massPhysics and ChemistryFigure 3 Allometric Scaling, retrieved from http://universe-review.ca/I10-83-metabolic.jpg, 18/12/2008ii. Physiological RegulationStrategies for coping with changing conditionsConformers – allow internal conditions tochange with external conditionsRegulators – maintain relatively constant internal conditions regardless of external conditions Figure 1.4. 2006HomeostasisMaintenance of internal conditions in the face of environmental perturbationsControlled by feedback loops or reflex control pathwaysNegative feedback loopsResponse sends a signal back to stimulus, reducing stimulusPositive feedback loopsHomeostasisFigure 1.4Antagonistic ControlsSet pointiii. Phenotype, Genotype, and the EnvironmentPhenotype is a product of genotype and its interaction with the environmentGenotype – genetic makeupPhenotype – observable traitsmorphology, physiology, and behaviorPhenotypic plasticity – single genotype generates more than one phenotype depending on environmental conditions Factors Influencing PhenotypeFigure 1.1Phenotype, Genotype, and the EnvironmentFigure 1.5Phenotypic PlasticityCan be irreversible or reversibleIrreversiblePolyphenism – developmental plasticityReversibleAcclimation – under laboratory conditionsAcclimatization – natural environmentiv. Physiology and EvolutionOne fundamental challenge of Animal Physiology is to:Understand and account for diversity of animal body form and strategies that animals use/have evolved to cope with their environmentsTwo types of questions (Evolutionary Physiologist)Proximate causeHow did this develop?Ultimate causeWhy are these changes helpful?Adaptive significanceAdaptationTwo distinct meaningsChange in a population over evolutionary time (i.e., many generations) Most common usageDefinition used in this bookSynonym for acclimationMany argue this is an incorrect usageBasis for Evolution and Natural SelectionVariation among individuals for specific traitsTraits must be heritableTraits must increase fitnessThat is, must increase reproductive successRelative fitness of different genotypes depends on the environmentIf the environment changes, the trait may no longer be beneficialNot All Differences are AdaptationsGenetic drift Random changes in the frequency of genotypes over timeIndependent of adaptive evolutionMost common in small populationsFor example, forest fire resulting in founder effectEvolutionary RelationshipsUnderstanding evolution is necessary to understanding physiological diversityDespite the diversity in animal form and function, there are many similaritiesCommon evolutionary ancestorsClosely related species share more features than distantly related speciesEukaryotes Invertebrates Animalia Arthropods InsectsRe?Familiarize yourself with the following:EnergyBondsWaterBiomoleculesEnzymes