BIOS1171 Lecture Notes - Lecture 5: Membrane Potential, Nernst Equation, Reflex Arc
22 Aug 2018
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Extracellular fluid: sodium (na+) 145mm [+, potassium (k+) 4mm [+, chloride (cl-) 120mm [-, anions (other ions to balance charge) Messages in the reflex arc are action potentials. 1 mole of an ion (6 x 1023 ions) 1mm (millimolar) = 6 x 1020 ions/litre: positive = 145 + 4 = 149, negative = 120, therefore 149 > 120, so there are more positive ions outside the cell than inside; so the cell is positive outside. Diffusion potential: equilibrium is reached when 2 forces equal each other, produces a potential difference in/out of the cell membrane (produces a voltage) Equilibrium potential of k+: equilibrium occurs when forces are equal, electric force measured in terms of electric potential, electric potential has units of volt (v, potential to get k+ into equilibrium = -97mv, cell is negative inside. Charge separation: only 3k+ out of 50,000k+ is required to produce equilibrium (very small) Membrane potential: since more k+ is conducted than na+ via the.
