Introduction to Physiological Principles Physiology

Introduction to Physiological Principles Physiology “The study of how animals work” Knut Schmidt-Nielsen (1915–2007) Structure and function of various parts How these parts work together/are integrated Diversity of animals More than 1 million species live on Earth Unifying themes Apply to all physiological processes History of Animal Physiology Hippocrates (460–circa 377 B.C.) Father of medicine Careful observation Aristotle (384–322 B.C.) Father of natural history Relationship between structure and function Claudius Galenus, “Galen” (129–circa 199) First experimental physiologist Systematic and carefully designed expts to probe the function of the body Detailed descriptions of anatomy Described the basis of many physiological processes Founder of Physiology History of Animal Physiology – cont’d Ibn al-Nafis (1213–1288) [Middle Ages] Anatomy of heart and lungs Andreas Vesalius (1514–1564) First modern anatomy textbook De Humani Corporis Fabrica Showed that Galen had made errors Triggered the modern study of anatomy and physiology William Harvey (1578–1657) Circulation of blood through the body by contractions of the heart Postulated closed circulation History of Animal Physiology – cont’d Herman Boerhaave and Albrecht von Haller (1700s) Bodily functions are a combination of chemical and physical processes Prior to this all physiologists were either Iatrochemists (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’d Matthias 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 environment Walter Cannon (1871–1945) “Homeostasis” History of Animal Physiology – cont’d Before 20th century, little distinction between animal physiology and medical physiology In 20th century, became interested in applying the emerging physiological principles to understand diversity Per Scholander (1905–1980) Comparative physiology C. Ladd Prosser (1907–2002) Central pattern generators Knut Schmidt-Nielsen (1915–2007) Animals in harsh and unusual environments History of Animal Physiology – cont’d George 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 subcellular Physiological Subdisciplines Based on and categorized by: Biological level of organization Process that causes physiological variation Ultimate goals of the research Many physiological questions encompass elements from each subdiscipline 1. Biological Level of Organization Cell and molecular physiology Genetics, metabolism, organelles Systems physiology Function of organs/interactions Organismal physiology Whole animal Ecological physiology Animal and its environment Integrative physiology Multiple levels of organization Biological Level of Organization – cont’d Figure 1.2 Biological Level of Organization Physiologists often study processes at more than one level Reductionism – understand a system by studying the function of its parts Emergence – the whole is more than the sum of its parts Physiologists are interested in these emergent properties – study interactions 2. Process that Causes Physiological Variation Developmental physiology Change as animal grows Environmental physiology Change in response to environment Evolutionary physiology Change due to natural selection Each can be addressed at any of the biological levels of organization 3. Ultimate Goals of the Research Pure physiology No specific goal, other than knowledge Applied physiology Medical physiology Comparative physiology Origins and nature of physiological diversity August Krogh principle – “For every biological system there is an organism on which it can be most conveniently studied” Model species Features conducive to experimentation Can provide insight into how process works in species of interest e.g. squid giant axon Unifying Themes in Physiology Physiological processes obey physical and chemical laws Physiological processes are usually regulated Homeostasis – maintenance of internal constancy Physiological phenotype is a product of genotype and environment Genotype – genetic makeup Phenotype – morphology, physiology, and behavior Genotype is the product of evolution i. Physics and Chemistry Physical properties of cells and tissue are linked to structure and function (e.g. bone) Molecular interactions are governed by chemical laws Thermodynamics and kinetics Electrical laws describe membrane function; especially excitable cells Body size has profound effects on physiological processes Allometric scaling Variables do not change linearly with body mass Physics and Chemistry Figure 3 Allometric Scaling, retrieved from http://universe-review.ca/I10-83-metabolic.jpg, 18/12/2008 ii. Physiological Regulation Strategies for coping with changing conditions Conformers – allow internal conditions to change with external conditions Regulators – maintain relatively constant internal conditions regardless of external conditions Figure 1.4. 2006 Homeostasis Maintenance of internal conditions in the face of environmental perturbations Controlled by feedback loops or reflex control pathways Negative feedback loops Response sends a signal back to stimulus, reducing stimulus Positive feedback loops Homeostasis Figure 1.4 Antagonistic Controls Set point iii. Phenotype, Genotype, and the Environment Phenotype is a product of genotype and its interaction with the environment Genotype – genetic makeup Phenotype – observable traits morphology, physiology, and behavior Phenotypic plasticity – single genotype generates more than one phenotype depending on environmental conditions Factors Influencing Phenotype Figure 1.1 Phenotype, Genotype, and the Environment Figure 1.5 Phenotypic Plasticity Can be irreversible or reversible Irreversible Polyphenism – developmental plasticity Reversible Acclimation – under laboratory conditions Acclimatization – natural environment iv. Physiology and Evolution One 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 environments Two types of questions (Evolutionary Physiologist) Proximate cause How did this develop? Ultimate cause Why are these changes helpful? Adaptive significance Adaptation Two distinct meanings Change in a population over evolutionary time (i.e., many generations) Most common usage Definition used in this book Synonym for acclimation Many argue this is an incorrect usage Basis for Evolution and Natural Selection Variation among individuals for specific traits Traits must be heritable Traits must increase fitness That is, must increase reproductive success Relative fitness of different genotypes depends on the environment If the environment changes, the trait may no longer be beneficial Not All Differences are Adaptations Genetic drift Random changes in the frequency of genotypes over time Independent of adaptive evolution Most common in small populations For example, forest fire resulting in founder effect Evolutionary Relationships Understanding evolution is necessary to understanding physiological diversity Despite the diversity in animal form and function, there are many similarities Common evolutionary ancestors Closely related species share more features than distantly related species Eukaryotes Invertebrates Animalia Arthropods Insects Re?Familiarize yourself with the following: Energy Bonds Water Biomolecules Enzymes