BIO 203 Lecture Notes - Lecture 2: Ideal Gas Law, Positive Feedback, Homeostasis
8 Sep 2017
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Document Summary
All life is constrained by the laws of physics and chemistry. Physical environment governs what cells can and can"t accomplish. Cells can utilize these laws to their advantage (i. e. signaling) The sa/v ratio is an index of relative sa for exchange. Therefore, as radius gets bigger, the sa/v ratio gets smaller and relative sa for exchange. All life can tolerate only a limited range of conditions. Salts, h 2 o, o 2 , co 2 , nutrients, waste elimination, temp, ph. The process of maintaining these conditions when tolerable ranges is called homeostasis. De(cid:128)nition of homeostasis : maintenance of relatively constant internal environment. All feedback systems have the following components: Sensor : measures some aspect of the internal. Integrator : compares the sensor measurement to a reference value (set point) (i. e. normal temp) E(cid:130)fector : the output of the system that changes the internal environment (i. e. high temp) *set point is the desired temp (i. e. 70 o f)
