The electrical Field within a polarized cell membrane is measured to be 4.0 kV/m

Question

The electrical Field within a polarized cell membrane is measured to be 4.0 kV/m. The thickness of the membrane is 9 nm. Find the transmembrane potential Problem 10.11 in the textbook (John Enderle). Explain what will happen when the Ag/AgCI gel of an ECG electrode used to monitor a patient in the ICU dries out over time. Problem 10.10 in the textbook (John Enderle). Cadmium and zinc electrodes arc placed in an electrolyte solution. Calculate the current that will flow through the electrodes if the equivalent resistance of the solution is equal to 14 kW. Problem 10.37 in the textbook (John Enderle). A pH electrode is attached to a sensitive voltmeter which reads 0. 652V when the electrode is immersed in a buffer solution with a pH of 6.7. After the pH electrode is moved to an unknown buffer solution, the reading of the voltmeter is decreased by 20%. Calculate the pH of the unknown buffer solution. Assume the temperature is 25 degree C. Problem 10.39 in the textbook (John Enderle). An unknown sample solution whose concentration is 1.55 10^-3 g/L is placed in a 1cm clear holder and found to have a transmittance (I/I_0) of 44%. The concentration of this sample is changed such that its transmittance has increased to 57%. Calculate the new concentration of the sample. (Problem 10.33 and 10.34 in the textbook (John Enderle)). Explain why the value of the normalized ratio (R) in a pulse oximeter is independent of the volume of arterial blood entering the tissue during systole and the skin pigmentation.

Explanation / Answer

In a pulse oximeter, the absorbance of infrared light traversing from the light emitter through the tissue and blood-vessels till it reaches the detector decreases and modulates according to the volume of blood flowing through the blood vessel and is dependent upon the red light absorbance by oxygenated hemoglobin. Since absolute values of oxygen saturation also change with distance of the red blood cell from the pulmonary bed and systolic pumping, a normalized value of oxygen saturation is normally determined. This normalized value of oxygen saturation provided by a pulse oximeter is dependent only upon the extent of light absorbed by oxygenated and deoxygenated hemoglobin. Thus, the rate of systole and skin pigmentation do not affect the extent of light absorption thus, do not affect the normalized or absolute values of provided by a pulse oximeter.

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