2011 Homeostasis and Passive Transport

2011 Homeostasis and Passive Transport - C - 1Dr. Kennon M.

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Unformatted text preview: C - 1Dr. Kennon M. GarrettHOMEOSTASIS AND PASSIVE SOLUTE TRANSPORT Reading: Widmaier et al., Vander’s Human Physiology, 12thed. pp. 5-12, 46-51, 96-102. Behavioral Objectives 1. Describe differences between negative and positive feedback systems. 2. List intracellular and extracellular concentrations of Na+, K+, Ca++, Mg++and Cl-. 3. List functions of membranes. 4. List characteristics of passive transport systems. 5. List variables that affect diffusion of solutes across membranes and know how changes in those variables affect diffusion of solutes. 6. List which types of solutes can and cannot diffuse across membranes and what types of solutes require transport system to pass across membranes. 7. List the types of channels and know their characteristics. 8. List characteristics of facilitated diffusion. I. Homeostasis Most physiological variables are maintained in a relatively constant range. In the late 1800s Claude Barnard recognized that the preservation of the stability of the “internal milieu” was essential for life. Walter Cannon coined term “homeostasis” in the 1930s to describe the process of maintaining the composition of extracellular fluid. Homeostasis is a dynamicprocess with continuousadjustments being made to maintain the variables in a range that is required for life. Each organ system contributes to the overall homeostasis of the organism. (Table 1-1) The physiological variables are maintained within a certain range by homeostatic control systems. These control systems include negative feedback and positive feedback, and feed forward systems. C - 2A. Negative Feedback 1. Negative feedback systems react to changes in the physiological variable to cause the variable to return to the normal values. 2. Negative feedback diagram Controlled variable – what is regulated Sensor – detects controlled variable Set point – ideal value of controlled variable Integrator – detects differences between set point and actual value of variable Effector – changes values of controlled variable Afferent pathway – information from sensor to integrator Efferent pathway – information from integrator to effector For homeostatic control systems, the controlled variableis a physiological variable such as blood pressure, body temperature, plasma sodium concentration, etc. In negative control homeostatic systems the sensormeasures the value of the controlled variable and sends this information to the integrator via an afferent pathway (carrying information to the integrator). The integratorcompares the value of the controlled variable with the set pointvalue for that variable. If there is a difference in the value and the set point, a signal is sent out to the effectorvia the efferent pathway(carrying information away from the integrator) to adjust the controlled variable back to the set point value....
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This note was uploaded on 10/01/2011 for the course PSYO 5016 taught by Professor Staff during the Fall '11 term at The University of Oklahoma.

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2011 Homeostasis and Passive Transport - C - 1Dr. Kennon M.

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