Lecture 19 - Nervous System I

All concentrations of ions have about a 30 40 times

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All concentrations of ions have about a 30-40 times difference between inside and  outside Na and Cl are way more common outside the cell than inside K is the reverse, very concentrated inside the cell
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There are other ions and these concentrations render both fluid compartments  electrically neutral The difference between in and out is what drives the AP Plasma membrane permeability to each ion is independently determined Na and K are usually the most important in determining RP, but Ca can play a role in  some cells Na/K differences inside and outside are determined by Na/K ATP-ase pumps that pump  Na out and K in RMP depends on Differences in specific ion []s  Differences in membrane permeabilities to specific ions The number of open channels in the membrane for each ion How do differences in Na and K create RMPs? A. Initially, no open channels, no ion flow No potential difference B. Open the K channels The membrane is permeable to only K and it will diffuse odwn its concentration gradient  towards the NaCl compartment This will cause a potential difference because after a few K ions leave the KCl  compartment will become negative Excess of positive on the left and excess of negative on the right Remember, neither Cl nor Na can move This will continue and the right will be more and more negative
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All the potential difference increases, the flow of K ions slows because the excess  negative charges attracts K and pulls it back This will balance with the chemical gradient and cause and equilibrium There will STILL be a charge difference This is what causes the RMP EQ potentials can be calculated Nernst equation If the concentration gradient is known 61 incorporates temperature, Universal Gas Constant, and faraday electrical constant If the resting membrane potential is negative, that means that the potassium is driving  the RMs Resting membrane potential is NOT the EQ potential of K, but it is closer the the K value  which means that K is more dominant K is more mobile across the membrane than Na
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