Topic 17 INTRODUCTION TO ANIMAL PHYSIOLOGY lecture 26 OBJECTIVES 1 Know the basic constraints on passive diffusion into and inside of organisms as modeled by the passive diffusion equation 2 Understand the basic physical interactions between an organism and its environment Physiology is the study of the physico chemical basis of function that is physical and chemical principles in conjunction with anatomical information are used to examine functional processes at the cell tissue organ and systemic multiple organ systems levels It is one of the oldest of all disciplines of biology Hierarchy of biological structure 1 cells individual independent units usually specialized for a particular function ca nerve cells muscle fibers cells red blood cells etc 2 tissue an aggregation of similar cells playing a common functional role epithelial tissue protection transport connective tissue support protection 3 organs a collection tissues which together perform a very specialized function ca stomach liver heart etc 4 organ systems assembly of organs which together are involved in a particular function table 40 1 is overview of the various organ systems in this last unit we will explore the digestive circulatory respiratory immune excretory endocrine nervous and muscular systems Interactions between processes going on internally and the environment Fig 40 10 animals are heterotrophs they obtain carbon from other organisms The process by which carbon compounds are catabolized is known as bioenergetics 1 2 3 4 5 6 food intake from the outside food processing and absorption cellular catabolism yielding ATP and waste heat waste heat is generally dissipated to the outside waste carbon compounds are eliminated the above processes must involve influx of oxygen and efflux of CO 2 water is also exchanged between the inside and the outside of the organism bottom line food oxygen and generally water must be transported in and wastes sometimes water and CO2 must be transported out 1 The design body plan and size of animal influence how materials can be transported in and out of organisms PASSIVE Diffusion recall in our discussion of membrane transport we said that diffusion in the passive movement of materials from areas of high concentration to areas of low concentration the principles of diffusion can also be applied to diffusion into and diffusion inside of an organism We can make the diffusion equation more accurate by adding another to term to it namely the distance through which the material is diffusing d J P x A x C d Where J rate of diffusion A area over which the material is diffusing C concentration gradient d diffusion distance If we change P to D the diffusion coefficient defines the intrinsic diffusivity of a substance in a material the equation becomes J D x A x C d what is important here is that J is directly proportional to D and indirectly proportional to d D values for many substances in organisms are low Furthermore the larger the animal the slower the rate of diffusion from the outside to the interior due to the fact that the d value is much larger There are important practical implicationsFig 40 7 small organisms unicellular or thin organisms Hydra can rely exclusively on the passive diffusion of substances in and out However larger organisms cannot they rely on convection convection the bulk movement of the medium air or fluid and all the materials dissolved or suspended in it Fig 40 8 the constraints of passive diffusion in relation to structural complexity size and activity have led to the evolution of a variety of bulk transport systems in animals 1 ingestion of food involves bulk movement of suspended or dissolved materials throughout GI tract absorbed nutrients are transferred to blood where there are moved by convection throughout 2 Oxygen and carbon dioxide movement in and out of respiratory system primarily by convection in large active organisms and gases are transported by convection in blood 3 Certain waste materials are transported out of the blood and into the urine where they leave the body by bulk transport 2
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