PreLab – Neuron Circuit Model Name:
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As the battery approaches full charge, the charge flow will stop Q = VC; V = IR Charging: VC = ε (1 - e-t / RC) I = (ε /R) e-t / RC ln(I) = ln(ε / R) – t / RC
Conversely, when the switch is thrown, in Figure 2, the capacitor starts discharging, initially the charge flow is greatest in the opposite direction while the voltage is dropping quickly.
Discharging: VC = Vo e-t / RC I = -Vo/R e-t / RC ln(I) = ln (-Vo / R) – t / RC
1. The most common name for Figure 1 is a(n) ______ circuit. Hint: Check your lab manual
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2. As discussed in Capacitors Pre-Lab and Neuron Circuit Model lab manual, t is called the _______; where t = RC.
Figure 5 represents the 3-step process for modeling the electronic pulse of the neuron.
3. The first step represents charging across the large resistance of the ___________.
4. The second step represents the opening of the lower resistance ______ channel.
5. The third step represents the opening of the very low resistance ________ channel causing a rapid discharge. |
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Below is data similar to today’s lab that is analogous to charging a neuron across its cell membrane that introduces a resistance of 3 MW. Analyze the data as requested in the lab manual.
y = m x + b ln(I) = (-1/τ) t + ln (ε / R)
(Note: To solve for ε to simplify you should use SI units and plot in Amps, not μA.)
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time (sec) |
0 |
15 |
30 |
45 |
60 |
75 |
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I (μA) |
82 |
74 |
67 |
60.5 |
54.5 |
49 |
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Use LineFit (or your favorite method) to graph the above data