Bioelectricity and Biophotonics Engineering Past Paper Notes PDF

WSC331 Bioelectricity and Biophotonics Engineering Felipe Iza P 3G Plasma and Pulsed Power Group Loughborough University, U.K. Slide S...

WSC331 Bioelectricity and Biophotonics Engineering Felipe Iza P 3G Plasma and Pulsed Power Group Loughborough University, U.K. Slide Set Bioelec 6 [email protected] www.lboro.ac.uk/eese/ourpeople 1 Recap from previous lecture Interior / Cytoplasm Im + IC Ik INa ICl Vm gk gNa gCl Cm Ek ENa ECl - Extracellular medium 2  Nernst and resting potentials  Nernst Potential: Equilibrium transmembrane potential for a single ion. “Electrical measure of the strength of diffusion of one ion.” e RT  C p  Ep  ln i Z p F  C p   Resting Potential: Equilibrium (Itotal=0) transmembrane potential when multiple ions are present. Weighted average of Nernst potentials based on the conductivities of the channels. Vm   gE p p Goldman-Hodgkin-Katz g p equation 3  Example Nerve (Squid axon) Intracellular Extracellular Conductance mM mM mS/cm2 K+ 397 20 0.415 Na+ 50 437 0.010 Cl- 40 556 0.582  What is the resting potential of a squid axon?  At the resting potential, is there any net current flowing across the membrane?  At the resting potential, is there any net flow of ions across the membrane? 4  Answer + Ik INa ICl gk gNa gCl Vm Ek ENa ECl - 25 20 E K  ln  74.7mV 1 397 g K 0.415 mS/cm2 25 437 E Na  ln 54.2mV g Na 0.010 mS/cm2 1 50 25 556 g Cl 0.582 mS/cm2 E Cl  ln  65.8mV 1 40 g K E K  g Na E Na  g Cl E Cl Vm   68mV g K  g Na  g Cl 5  Ionic currents ENa 0 ECl -68 Vm EK VVmm>E >EKK   IIKK>0>0 ?   efflux of potassium influx/efflux of potassium ions ions? VVmm