BIO 365R lecture 5 - The action potential Threshold...

Info iconThis preview shows pages 1–15. Sign up to view the full content.

View Full Document Right Arrow Icon
The action potential Threshold • overshoot • peak of AP • repolarization • after hyperpolarization • refractory period •All-or-none (I) Refractory period 1 msec.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Voltage clamp circuitry
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The early current is carried by Na + A B C D
Background image of page 4
Pharmacological dissection of I K and I Na TEA TTX Note: I Na is brief
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
I-V curves (current-voltage curves) Na + reversal potential = E Na
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Why does the I-V curve for the Na + current look so weird? Note: This is an I-V curve made by plotting the peak amplitude of the Na + current at each voltage. Leao et al., 2005
Background image of page 8
Why does the I-V curve for the Na + current look so weird? Leao et al., 2005 Na + channels start to open at this voltage All the Na + channels are open at this voltage NO Na + channels open when at or below - 60 mV ALL Na + channels open when at or above -20 mV
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Why does the I-V curve for the Na + current look so weird? Leao et al., 2005 Na + channels start to open at this voltage All the Na + channels are open at this voltage NO Na + channels open when at or below - 60 mV ALL Na + channels open when at or above -20 mV High Driving force Low
Background image of page 10
How do we explain the weird I-V curve for Na + ? 1) The driving force for Na + ions is greatest when the membrane potential is at rest. It decreases as the membrane potential becomes more positive, becomes 0 when the membrane is at E Na and reverses if we clamp the cell to values more positive than E Na (which cannot happen normally). 2) No channels are open at rest (or hyperpolarized potentials; all channels are open ~ -20 mV. I Na = g Na ( V m " E Na )
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Na + reversal potential = E Na The Na + current becomes outward at voltages more positive then E Na .
Background image of page 12
The early current is carried by Na + A B C D
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
What happens to E Na
Background image of page 14
Image of page 15
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/12/2009 for the course BIO 51340 taught by Professor Zakon during the Spring '09 term at University of Texas at Austin.

Page1 / 34

BIO 365R lecture 5 - The action potential Threshold...

This preview shows document pages 1 - 15. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online