HW1_Solutions - BME 365R Quantitative Physiology Homework 1...

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BME 365R Quantitative Physiology Homework 1 Due September 9, 2009; 12:30PM 1. (25 points) Review the article on Induced Hypothermia posted on Blackboard in the HW1 folder. A. Select three physiological systems mentioned in the section “physiologic effects of IH” and identify at least two effects of induced hypothermia for that system (you should have 6 effects). B. Review the section entitled “Clinical Applications of IH” and select three clinical applications of IH and indicate whether IH is generally accepted, somewhat accepted, controversial or not generally accepted and provide a brief explanation supporting your answer in each case. 2. (25 points) In the process of action potential propagation, voltage gated Na channels open when the membrane potential rises about 20 mV above the rest potential; this potential is called the "threshold". Subsequent to reaching the threshold, about 5 x 10 8 Na + ions rush into the cell over a time period of 0.5 ms; A. What is the average value of the Na + ion current in MS units into the cell over the 0.5ms? Current is: I=e(5  10 8 )/(0.5 10 -3 )=16 10 -8 A = 0.16 uA B. If the average electrical potential across the membrane (inner potential less outer potential) while the Na + ions enter the cell is -25mV, what is the electrical power associated with the influx of Na + ions? Power is the effort X flow: Power (Watts)=0.025 X 0.16 10 -6 =4 nW C. If you consider the membrane as a generic electrical element (e.g., resistor or capacitor), what is the sign (positive or negative) of electrical power
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HW1_Solutions - BME 365R Quantitative Physiology Homework 1...

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