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Homework 3 Solutions

# In the table 101 webster 4th ed pco2 3348 mmhg

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Unformatted text preview: l − ]S + Ⱥlog I0 + + log[Cl − ]G Ⱥ ln10 ⋅ kT q Ⱥ Ⱥ Ⱥ −0.5 Ⱥ = − log[Cl − ]S + Ⱥ−6 + − 3Ⱥ Ⱥ 60 m Ⱥ € = − log[Cl − ]S 17.3 c. Next assume the membrane is permeable only to Ca2+ and the trapped Ca2+ concentration between the membrane and the gate of the ISFET is 1 mmol/L. As before derive and sketch, on logarithmic axes, the drain current as a function of Ca2+ concentration. For Ca2+, z = +2: Ⱥ Ⱥ 1 −VTH 1 log( I DS ) = ⋅ log[ A z ]S + Ⱥlog I0 + − ⋅ log[ A z ]G Ⱥ z ln10 ⋅ kT q z Ⱥ Ⱥ Ⱥ Ⱥ −VTH = 0.5 ⋅ log[Ca 2+ ]S + Ⱥlog I0 + − 0.5 ⋅ log[Ca 2+ ]G Ⱥ ln10 ⋅ kT q Ⱥ Ⱥ Ⱥ Ⱥ −0.5 = 0.5 ⋅ log[Ca 2+ ]S + Ⱥ−6 + + 1.5Ⱥ Ⱥ Ⱥ 60 m € = 0.5 ⋅ log[Ca 2+ ]S − 12.8 Slopes are 1,  ­1 and 0.5 respectively. Problem 3: Short response (no more than one paragraph each). a. What is a rheobase current and where is it used? The Strength ­Duration Curve for a typical neural membrane flattens out with long stimulus durations, reaching an asymptote called the RHEOBASE. When the stimulus strength is below the rheobase, stimulation is ineffective even when stimulus duration is very long. The rheobase tells the minimum strength of stimulation for effective stimulation. Source: http://en.wikipedia.org/wiki/File:Rheobase_chronaxie.png http://www.medicine.mcgill.ca/physio/vlab/cap/S ­D.htm b. What is the difference between macroshock and microshock? Macroshock: Current is applied externally and flows throughout the body. A small fraction of total current flows through the heart. Safety limit: 10 ­20 mA Microshock: Invasive devices apply current. All current...
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