Introduction to Physiological Principles

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Grading for the first term * ATTENDANCE IN ALL LABS IS MANDATORY. **MIDTERMS: Combinations of multiple choice, short answers, long answers. Note: ALL midterms, class presentations, research paper and lab requirements must be completed to obtain a passing grade in the course.

Research Paper Use peer-reviewed journal papers (since 2005) as source of your research paper. 3 - 5 word-processed pages (not including references or figures/tables). Structure : Title page, Abstract/Summary, Main text (depending on the topic you selected, you can have several subheadings in this section), Conclusion, References, Tables, List of figures and figures. The grading criteria: originality and relevance of the topic; thorough understanding of the cited papers; clarity of presentation; organization of the presentation in an easy to follow/understood format.

Physiology “The study of how animals work” Knut Schmidt-Nielsen (1915–2007) Structure and function of various parts How these parts work together Diversity of animals More than 1 million species live on Earth Unifying themes Apply to all physiological processes

Physiological Subdisciplines Based on Biological level of organization Process that causes physiological variation Ultimate goals of the research Many physiological questions encompass elements from each subdiscipline

Biological Level of Organization Organismal physiology Systems physiology Ecological physiology Cell and molecular physiology Integrative physiology 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

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

Ultimate Goals of the Research Pure physiology No specific goal, other than knowledge Applied physiology Medical physiology Comparative physiology August Krogh principle – “For every biological system there is an organism on which it can be most conveniently studied”

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

Physics and Chemistry Physical properties of cells and tissue are linked to structure and function (linked to molecular structure) Molecular interactions are governed by chemical laws Thermodynamics and kinetics Electrical laws describe membrane function; especially excitable cells Membrane potential used to send signals within and between cells (i.e. nerves and muscles)

Physics and Chemistry Body size influences physiological patterns Allometric scaling Figure 1.3

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

Homeostasis Maintenance of internal conditions in the face of environmental perturbations Animals initiate specific responses to control/regulate a particular variable Some strategies are effective in the short term Some strategies require significant resources and longer time to take effect Some stressors are predictable (often cyclic) Cyrcadian Sesonal Lunar cycles

Homeostasis Controlled by feedback loops or reflex control pathways Antagonistic controls – independent regulators with opposite effects Negative feedback loops Positive feedback loops Figure 1.4

Phenotype, Genotype, and the Environment Phenotype is a product of genotype and its interaction with the environment Genotype – genetic makeup Phenotype – morphology, physiology, and behavior

Factors Influencing Phenotype Figure 1.1

Phenotypic plasticity Single genotype generates more than one phenotype depending on environmental conditions. Can be irreversible or reversible Irreversible Polyphenism – developmental plasticity Reversible Acclimation – under laboratory conditions Acclimatization – natural environment Figure 1.5

Phenotypic Plasticity - Polyphenism

Physiology and Evolution Diversity of anatomic and physiologic strategies animals use to cope with their environment Two types of questions Proximate cause How did these develop? Ultimate cause Why are these changes helpful?

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 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 Understanding evolution is necessary to understanding physiological diversity

Unifying Themes in Physiology Table 1.1