Physiology. Biol 219 Lec 1 Fall The Science of Body Function. Themes of Physiology. Themes of Physiology

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1 Physiology The Science of Body Function Themes of Physiology 1. Physical-chemical basis of body function Scientific method to study and understand the body Descriptive and quantitative Focus on processes and mechanisms. Themes of Physiology 1. Physical-chemical basis of body function 2. Structure-function relationships Body function depends on structure at all levels of biological organization. 1

2 Levels of Organization Ø Chemical basis of biological function: water, ions, organic molecules Ø The cell is the basic unit of life. Ø Tissues are the living fabric of the body. Ø Organs perform specific physiological functions. Ø Organ systems perform major physiological processes. Ø The organism is the most complex and integrated level. Themes of Physiology 1. Physical-chemical basis of body function 2. Structure-function relationships 3. Energy use The body needs a continuous supply of energy. Cells get energy through metabolism of high-energy molecules: cellular respiration. Cellular Respiration: Harvesting Energy to form ATP 2

3 Themes of Physiology 1. Physical-chemical basis of body function 2. Structure-function relationships 3. Energy use 4. Homeostasis Maintenance of relatively constant internal conditions in the body Themes of Physiology 1. Physical-chemical basis of body function 2. Structure-function relationships 3. Energy use 4. Homeostasis 5. Integration Organs and organ systems are functionally connected and work together to sustain life. Integration of Organ Systems Ø Organ systems work together to maintain body function Ø Organ systems share a common, regulated internal environment. Ø The nervous system and endocrine system control other organ systems. Ø The circulatory system transports and exchanges materials with other organ systems. 3

4 Environments and Fluid Compartments External Environment Intracellular Fluid (ICF) Extracellular Fluid (ECF) Ø The ICF (cytosol) is contained within trillions of individual cells Ø The ECF consists of the interstitial fluid and the blood plasma. Ø The ECF is the internal environment of the body. The ICF makes up about ⅔ of total body water The ECF makes up about ⅓ of TBW (interstitial fluid + blood plasma) 4

5 The ICF and the ECF have different chemical composition. ECF ICF ECF ICF ECF K + Na + A Cl ICF ICF ECF ICF Ø Most solutes in the ICF and ECF are ions Boundaries Between Environments 1. The cell membrane forms the boundary between the ICF and the ECF. Cell membrane(s) Questions: What molecules make up the structure of the cell membrane? How are these molecules arranged in the cell membrane? Structure of the Cell Membrane (plasma membrane) 5

6 Boundaries Between Environments 2. Epithelium forms the boundary between the internal environment (ECF) and external environment. Epithelium General Structure of Epithelium free surface Ø Epithelial tissues cover and line organs. Inter nal envir onm ent (ECF) Ø The free surface faces the external environment or the lumen of a hollow organ. Ø Epithelial tissue also forms glands. Questions: What are some common subtypes of epithelium? What are some specific locations for each subtype? Homeostasis Maintenance of relatively constant internal conditions in the body 6

7 1. Homeostasis is a steady state process (law of mass balance) 2. Energy is required to maintain homeostasis The sodium-potassium pump uses energy from ATP to maintain homeostasis of the ICF and ECF. 7

8 3. The ECF (= internal environment) is regulated to maintain suitable and stable conditions for the cells. Variable Normal Values body temperature 37ºC arterial blood pressure 120/75 mm Hg (mean 90 mm Hg) arterial ph 7.4 arterial PO2 100 mm Hg arterial PCO2 40 mm Hg blood glucose concentration 90 mg/dl plasma osmolarity 290 mosm 4. Homeostasis is maintained by negative feedback control. Stimulus: change in Response: Homeostatic Control of Body Temperature physiological variables are maintained in relation to a set point corrective response is in the opposite direction of the change away from the set point 8

9 Example: Homeosatic Regulation of Body Temperature Homeostatic control of body temperature: physiological responses to cold. Set point = 37ºC + + Positive Feedback non-homeostatic results in rapid change of a physiological variable 9

10 The LH surge triggers ovulation: an example of positive feedback. 10