BIO%20203.09%20Lecture%202s

BIO%20203.09%20Lecture%202s - BIO 203 Lecture 2...

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1 BIO 203: Lecture 2 - Physiological Ecology Prof. William Collins Office: 534 Life Sciences Building Office Hours: Mondays, 9:00 - 10:00 PM (on-line) Tuesdays, 11:30 AM - 12:30 PM Thursdays, 4:00 - 5:00 PM All Life Can Tolerate Only a Limited Range of Conditions • Conditions include: salts, H 2 O, O 2 , CO 2 , nutrients, waste elimination, temperature, pH, ……… The process of maintaining these conditions within tolerable ranges is called homeostasis • Definition of Homeostasis: maintenance of a relatively constant internal environment Requires cell-to-cell communication • Nervous system, hormonal system, intrinsic system Requires negative feedback
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2 Feedback Systems • All feedback systems have the following components: Sensor : measures some aspect of the internal environment (e.g., temp) Integrator : compares the sensor measurement to a reference value (set point ) (e.g., normal temp) Effector : the output of the system that changes the internal environment (e.g., increases temp) Thermostat Example of Negative Feedback Sensor detects temp Set Point is the desired temperature - e.g., 70 o F Integrator compares temp to Set Point 75 o F too warm 65 o F too cold Turn on AC cool air reduce temp Turn on heat warm air increase temp
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3 Negative Feedback Too warm, turn on AC Too cold, turn on heat Effector counteracts (is opposite to) stimulus Set point Room Temperature Time Regulatory System: Types of Feedback • Negative Feedback The effector counteracts the initial sensor stimulus • e.g., an increase in temperature measured by the sensor results in the effector causing a decrease in temperature Critical for maintaining homeostasis • Positive Feedback The effector increases the initial sensor stimulus • e.g., an increase in temperature measured by the sensor results in the effector causing a further increase in temperature Leads to rapid changes
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BIO%20203.09%20Lecture%202s - BIO 203 Lecture 2...

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