BIO2A03-2011-L21 - Biology2A032009 Lecture21 Recall:

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Biology 2A03 -2009 Lecture 21
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Recall: Equilibrium potential (E N ) via the Nernst Equation E N  = “A hypothetical value for the membrane potential at which the electrical  driving force is equal and opposite to the chemical driving force producing an  electrochemical driving force of zero.” If E N  = E M  for an ion then  no electrochemical driving force   acting on it to move  in or out of the cell. If E N  ≠ E there will be a driving force for that ion in or out of the cell  depending on the  direction and size of the force . (E N ) for Na + : = 61 log [145 mM]    =      +60 mV               [15 mM] For example  Na requires large positive outward directed electrical force (that is far  from E M ) to counteract a large  inward concentration gradient . So Na has a large  driving force for inward movement.
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Fig  8.10, pg  225 We a k S tim ulus S tro ng  S tim ulus Inhibitory, K + Cl - G.P. is “graded” in proportion to the strength of the stimulus Increased G Na +   Increased G K + or G Cl -
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G.P’s at synapses on dendrites or soma are  Post-Synaptic Potentials threshold threshold At e xc ita to ry s yna ps e s , the  ne uro - tra ns m itte r g e ne ra lly o pe ns  b o th  Na + K +  c ha nne ls  ==> inc re a s e d G Na+ inc re a s e d G K+ ==> ne t de po la riza tio n “Exc ita to ry Po s t-S yna ptic  Po te ntia l
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This note was uploaded on 04/12/2011 for the course BIOL 2A03 taught by Professor Mccelland&dej during the Winter '11 term at McMaster University.

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BIO2A03-2011-L21 - Biology2A032009 Lecture21 Recall:

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