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8 Cards in this Set
- Front
- Back
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what can a voltage clamp measure?
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current as a function of time
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what are gk / gna dependent on?
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voltage and time
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How do we know na and k channels differ?
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1. substitute choline for Na and no AxP
2. radioisotopes for Na/K and measure accumulation of ions entering/leaving 3. voltage clam |
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How does myelin increase velocity of an AxP?
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The myelin layer contributes a high total membrane resistance - resistances in series, and a lower total membrane capacitance - capacitances in series. This increases the velocity because there is less accumulated charge on the membrane to be discharged, so the membrane charges faster and at a longer distance ahead of the action potential.
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does tau (time constant) depend on radius?
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NO! independent of radius because
tau =Rm*Cm ohms cm2 * F/cm2 |
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what's the safety mechanism in AxP propagation?
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saltatory conduction allows you to miss one node
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What explains the threshold ionic situation?
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So it's a battle between the voltage-sensitive Na channels and the non-voltage-sensitive K channels (that are mostly responsible for the resting potential).
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what gives upper limit to AxP firing frequency?
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absolute refractory period
requires hyperpolarization and time |
