Physiology of Excitable Cells - Membrane Biophysics - Flashcards in University Biology

1. measure of ability to pass ionic current (s) allows us to see voltage dependent behaviour independent of driving force (11)
7. increases conduction velocity of nerve axon because myelin increases Rm and lowers Cm. allows action potential to be conducted very rapidly from one node of Ranvier to next, making AP appear to jump from node to node in form of conduction = SALTATORY (11)
8. measure value where concentration gradient and electrical gradients balance each other = EA = (58/z)log10(([A]o/[A]i)) - theoretical assumes membrane perfectly selective for that ion (6, 8)

2. cant be predicted precisely, independent behaviour of individual channels (10, 9)
3. Two voltage dependent gates ( activation and inactivation), resting - closed, depolarisation - open, 4 homologous domains, each domain six transmembrane segments (2, 8)
4. technique of controlling membrane potential and measuring current to rapidly return membrane potential to chosen level, compensates (therefore measures) current. Clamps voltage and providing current equal and opposite - can measure current (7, 5)
5. τ=R*C equals time taken for voltage to rise exponentially by 63% of the difference between its initial and final values (4, 8)
6. closed and open state, tetramers -4 identical peptide units channels can co assemble with subunits - diff sub groups - increasing functional diversity. (1, 8)
9. Distance over which the change in potential decreases to 1/e (37%) of its maximal value. increasing axonal diameter increases length constant, decreasing Rm increases leak conductance - decrease in length constant. Dependent on Rm and Ra = √(Rm/Ra) (6, 8)
10. selectivity filter in closed state. Open state - inner helices apart - aperture permitting ions to move through. Closed state - inner helices bundled - narrows pore preventing ions to pass through (3, 7, 6)

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