Lecture 4 Action Potential _ Ion Channels web

Lecture 4 Action Potential _ Ion Channels web - The Action...

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The Action Potential & n Channels Ion Channels Chapter 4
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Announcements FIRST QUIZ: posted on Sakai: 10 questions Submit on-line: DEADLINE 10 PM Friday, Sept. 17 STUDY GROUP: Professor Charles Page ednesday mornings: 10:15 1:15 Wednesday mornings: 10:15 11:15 • Room 336 MSLC, ARC Bldg Busch Campus irst meeting: September 15 th First meeting: September 15
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ction Potential (AP) Action Potential (AP) • Rapid change in Vm – Changes from inside negative to positive & back to resting negative haracteristics • Characteristics 1. ____________triggered by ‘depolarization’ to ~ -40 mV 2. _______________irrespective of strength, if stimulus is above reshold amplit de & form of 1 msec threshold, amplitude & form of AP are constant 3. period: ‘absolute’ & _________ p ‘relative’
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Voltage clamp technique V m is held constant (‘clamped’) at a set value (‘command voltage’) by current passing electrode. Current injected by amplifier is equal (and opposite) to current across membrane caused by evoked change in conductance.
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oltage clamp recording Voltage clamp recording Depolarization results in a transient _______current, and a ________, maintained outward current
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Removing Na + from ECF affects _____ current, ut not urrent but not ________ current 1 3 2 4
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TTX blocks the sodium current TEA blocks the potassium current Tetrodotoxin, TTX, (found in puffer fish), selectively blocks Na + channels etraethylammonium TEA blocks K + hannels Tetraethylammonium, TEA, blocks K channels Hodgkin & Huxley calculated voltage- and time- dependent changes in g na and g k by rearranging equation for current: g ion = I ion /(Vm – E ion )
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Calculation of ____ & ___ from voltage clamp data: ____ = I ion /(Vm – E ion )
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Voltage clamp data mostly supported earlier hypothesis of AP & provided new insights • _______ dependency of g na embrane depolarization above threshold crease – membrane depolarization above threshold increase in g na – increased Na influx ‘depolarization’ further increase in g na
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This note was uploaded on 10/03/2010 for the course RUT 146:356 taught by Professor Gol during the Spring '10 term at Rutgers.

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Lecture 4 Action Potential _ Ion Channels web - The Action...

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