Kip McGilliard Eastern Illinois University Lauralee Sherwood Hillar Klandorf Paul Yancey Chapter 1 Homeostasis and Integration: The Foundations of Physiology

1.1 Introduction  Characteristics of living things Organize themselves using energy and raw materials from their surroundings (metabolism) Maintain integrity in the face of disturbances (homeostasis) Reproduce

1.1 Introduction  Explanation of biological adaptations Mechanistic (proximate) explanation Emphasizes mechanisms Cause-and-effect sequences Evolutionary (ultimate) explanation Variation and natural selection Species must cope with selective pressures Adaptations -- beneficial features that enhance overall survival of the species

1.1 Introduction  Adaptations reflect evolutionary history including cost-benefit trade-offs Example: Shivering in mammals Cost -- requires energy Benefit -- maintains body temperature in the cold

1.1 Introduction  Physiology is an integrative discipline Closely interrelated with anatomy, physics, chemistry, biochemistry, molecular biology, and genetics  Physiology is a comparative discipline Comparing physiological features in different types of organisms Krogh principle -- for every adaptation, there will be a particular species in which it is most conveniently studied

1.2 Methods in Physiology  Scientific method 1.Ask a question about nature 2.Propose alternative hypotheses to explain the phenomenon Hypothesis = Tentative explanation about some aspect of nature Induction = Taking specific information and creating a general explanation Hypotheses must be testable and falsifiable

1.2 Methods in Physiology  Scientific method 3.Design experiments that test the hypothesis by making testable predictions Deduction = Making specific predictions based on a hypothesis and testing those predictions 4. Conduct experiments 5. Refine earlier questions and hypotheses, and design new tests

1.2 Methods in Physiology  Scientific method When a hypothesis has been consistently supported and all alternative hypotheses have been falsified, a hypothesis may be elevated to a scientific theory.

1.3 Levels of Organization in Organisms  Basic functions essential for survival of the cell Self-organization Self-regulation Self-support and movement Self-replication

1.3 Levels of Organization in Organisms  Examples of specialized functions of some cells Gland cells secrete digestive enzymes. Neurons generate and transmit electrical impulses. Kidney cells selectively retain needed substances while eliminating unwanted substances in the urine. Muscle cells produce movement.

Figure 1-2 p8 (a) Chemical level: a molecule in the membrane that encloses a cell (b) Cellular level: a cell in the stomach lining (c) Tissue level: layers of tissue in the stomach wall (d) Organ level: the stomach (e) Body system level: the digestive system (f) Organism level: the whole body

1.4 Size and Scale among Organisms  Organisms range in size from unicellular prokaryotes to large multicellular eukaryotes over a scale of  Scaling = Study of the effects of size on anatomy and physiology

1.4 Size and Scale among Organisms

 Larger organisms have smaller surface- area-to-volume ratios Surface area is related to the square of the radius Volume is related to the cube of the radius Advantage of smaller surface-area-to-volume ratio (larger animals) -- better retention of heat Disadvantage -- reduced ability to obtain enough nutrients to meet the needs of the larger volume

1.5 Homeostasis: Basic Mechanisms and Enhancements  Claude Bernard documented the ability of mammals to maintain a relatively constant state of the internal environment (milieu interieur).  Walter B. Cannon coined the term “homeostasis”  Homeostasis = Maintenance of a consistent internal state  Homeostasis is not a fixed state, but a dynamic steady state.

1.5 Homeostasis: Basic Mechanisms and Enhancements  Majority of cells in a multicellular organism are not in direct contact with the external environment.  The internal environ- ment consists of the extracellular fluid. Plasma Interstitial fluid

Homeostasis is essential for proper cell function, and most cells, as a part of an organized system, contribute to homeostasis 1.5 Homeostasis: Basic Mechanisms and Enhancements

 Homeostatically regulated factors of the internal environment Concentration of energy-rich molecules Concentration of O 2 and CO 2 Concentration of waste products pH Concentration of water, salt, and other electrolytes Volume and pressure Temperature Social parameters

1.5 Homeostasis: Basic Mechanisms and Enhancements  Animals vary in their homeostatic abilities (e.g. thermoregulation) Regulators Use internal mechanisms to defend a relatively constant state Conformers Internal state varies with that of the environment Avoiders Minimize internal variations by avoiding environmental disturbances

1.5 Homeostasis: Basic Mechanisms and Enhancements  Negative feedback is the main regulatory mechanism for homeostasis Negative feedback occurs when a change in a controlled variable triggers a response that opposes the change.

1.5 Homeostasis: Basic Mechanisms and Enhancements  Components of a negative feedback system Sensor -- Measures the variable being regulated Integrator -- Compares the sensed information with a set point Effector -- Makes the corrective response  Examples Control of room temperature Mammalian thermoregulation

1.5 Homeostasis: Basic Mechanisms and Enhancements

1.6 Regulated Change  Positive feedback systems Output is continually enhanced so that the controlled variable continues to move in the direction of the initial change. Create rapid change Example: Oxytocin release and uterine contractions during mammalian birth

1.6 Regulated Change

 Disruptions in regulation can lead to illness and death. Pathophysiology -- altered physiology of organisms associated with disease Example: Congestive heart failure is a positive feedback cycle leading to death

1.7 Organization of Regulatory and Organ Systems  Homeostasis and other regulation is hierarchically distributed. Regulation at the cellular level Intrinsic controls Regulation by a tissue or organ for its own benefit Extrinsic controls Regulatory mechanisms initiated outside an organ to alter its activity Coordinated regulation of several organs toward a common goal

1.7 Organization of Regulatory and Organ Systems  Organ systems can be grouped according to their contributions to the organism. Maintenance systems Circulatory system Immune system Respiratory system Excretory system Digestive system Integumentary system Reproductive system

1.7 Organization of Regulatory and Organ Systems

 The physiology of an animal is well suited to the environment in which it has evolved. This is explained by the process of ADAPTATION- gradual change over many generations.  Acclimatization is a change of an individual over its lifetime of biochemical or anatomical alterations  Acclimation is like acclimatization but induced by experimentation.